pygsti.objectivefns.objectivefns
Defines objectivefunction objects
Module Contents
Classes
A factory class for building objective functions. 

So far, this is just a base class for organizational purposes 

An objective function that acts on probabilities and counts directly. 

Contains all the information that we'd like to persist when performing 

Additionally holds quantities at a specific modelparameterspace point. 

An objective function whose probabilities and counts are given by a Model and DataSet, respectively. 

The function N(pf)^2 / p 

The function N[x + 1/(alpha * x^alpha)  (1 + 1/alpha)] where x := p/f. 

The function N(pf)^2 / f 

The function custom_weight^2 (pf)^2, with custom weights that default to 1. 

The function N*f*log(f/p)  N*(fp). 

The function N*f*log(f/p). 

The function N*f*log(f) (note this doesn't depend on the probability!). 

The function 0.5 * pf. 

A timeindependent modelbased ( 

Modelbased chisquared function: N(pf)^2 / p 

Modelbased chialpha function: N[x + 1/(alpha * x^alpha)  (1 + 1/alpha)] where x := p/f. 

Modelbased frequencyweighted chisquared function: N(pf)^2 / f 

Modelbased customweighted chisquared function: cw^2 (pf)^2 

Modelbased poissonpicture delta loglikelihood function: N*f*log(f/p)  N*(fp). 

Modelbased delta loglikelihood function: N*f*log(f/p). 

Modelbased maximummodel loglikelihood function: N*f*log(f) 

Modelbased TVD function: 0.5 * pf. 

A timedependent modelbased objective function 

Chisquared function that can handle timedependent circuits and data. 

Poissonpicture delta loglikelihood function that can handle timedependent circuits and data. 

A wildcardbudget bolton to an existing objective function. 

Holds various values of an objective function at a particular point. 
 class pygsti.objectivefns.objectivefns.ObjectiveFunctionBuilder(cls_to_build, name=None, description=None, regularization=None, penalties=None, **kwargs)
Bases:
pygsti.baseobjs.nicelyserializable.NicelySerializable
A factory class for building objective functions.
This is useful because often times the user will want to specify some but not all of the information needed to create an actual objective function object. Namely, regularization and penalty values are known ahead of time, while the model, dataset, and circuits are supplied later, internally, when running a protocol.
Parameters
 cls_to_buildclass
The
MDCObjectiveFunction
derived objective function class to build. namestr, optional
A name for the built objective function (can be anything).
 descriptionstr, optional
A description for the built objective function (can be anything)
 regularizationdict, optional
Regularization values (allowed keys depend on cls_to_build).
 penaltiesdict, optional
Penalty values (allowed keys depend on cls_to_build).
 classmethod cast(obj)
Cast obj to an ObjectiveFunctionBuilder instance.
If obj is already an ObjectiveFunctionBuilder instance, it is simply returned. Otherwise a new ObjectiveFunctionBuilder instance is created from obj if possible.
Parameters
 objNone or str or dict or list or tuple or ObjectiveFunctionBuilder
Object to cast.
Returns
ObjectiveFunctionBuilder
 classmethod create_from(objective='logl', freq_weighted_chi2=False)
Creates common
ObjectiveFunctionBuilder
from a few arguments.Parameters
 objective{‘logl’, ‘chi2’}, optional
The objective function type: loglikelihood or chisquared.
 freq_weighted_chi2bool, optional
Whether to use 1/frequency values as the weights in the “chi2” case.
Returns
ObjectiveFunctionBuilder
 compute_array_types(method_names, forwardsim)
 build(model, dataset, circuits, resource_alloc=None, verbosity=0)
Build an objective function. This is the workhorse method of an
ObjectiveFunctionBuilder
.Arguments are the additional information needed to construct a
MDCObjectiveFunction
object, beyond what is stored in this builder object.Parameters
 modelModel
The model.
 datasetDataSet.
The data set.
 circuitslist
The circuits.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for objective function computations.
 verbosityint, optional
Level of detail to print to stdout.
Returns
MDCObjectiveFunction
 build_from_store(mdc_store, verbosity=0)
Build an objective function. This is a workhorse method of an
ObjectiveFunctionBuilder
.Takes a single “store” argument (apart from verbosity) that encapsulates all the remaining ingredients needed to build a
MDCObjectiveFunction
object (beyond what is stored in this builder object).Parameters
 mdc_storeModelDatasetCircuitsStore
The store object, which doubles as a cache for reused information.
 verbosityint, optional
Level of detail to print to stdout.
Returns
MDCObjectiveFunction
 class pygsti.objectivefns.objectivefns.ObjectiveFunction
Bases:
object
So far, this is just a base class for organizational purposes
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
For instance, if the objective function is DeltaLogL then this function would multiply objective_function_value by 2, whereas in the case of a chisquared objective function this function just return objective_function_value.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 class pygsti.objectivefns.objectivefns.RawObjectiveFunction(regularization=None, resource_alloc=None, name=None, description=None, verbosity=0)
Bases:
ObjectiveFunction
An objective function that acts on probabilities and counts directly.
Every
RawObjectiveFunction
is assumed to perform a “local” function elementwise on the vectors of probabilities, counts (usually for a single outcome), and totalcounts (usually for all the outcomes in a group), and sum the results to arrive at the final objective function’s value.That is, the function must be of the form: objective_function = sum_i local_function(probability_i, counts_i, total_counts_i).
Each element of this sum (local_function(probability_i, counts_i, total_counts_i)) is called a term of the objective function. A vector contains the squareroots of the terms is referred to as the leastsquares vector (since leastsquares optimizers use this vector as their objective function) and is abbreviated “lsvec”.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 set_regularization()
Set regularization values.
 fn(probs, counts, total_counts, freqs)
Evaluate the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
Returns
float
 jacobian(probs, counts, total_counts, freqs)
Evaluate the derivative of the objective function with respect to the probabilities.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
Returns
 numpy.ndarray
A 1D array of length equal to that of each argument, corresponding to the derivative with respect to each element of probs.
 hessian(probs, counts, total_counts, freqs)
Evaluate the Hessian of the objective function with respect to the probabilities.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
Returns
 numpy.ndarray
A 1D array of length equal to that of each argument, corresponding to the 2nd derivative with respect to each element of probs. Note that this is not a 2D matrix because all offdiagonal elements of the Hessian are zero (because only the ith term depends on the ith probability).
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec_and_lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the leastsquares vector together with the vector itself.
This is sometimes more computationally efficient than calling
dlsvec()
andlsvec()
separately, as the former call may require computing the latter.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 dlsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of sqrt(local_function) at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 abstract zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 abstract zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 abstract zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.ModelDatasetCircuitsStore(model, dataset, circuits=None, resource_alloc=None, array_types=(), precomp_layout=None, verbosity=0)
Bases:
object
Contains all the information that we’d like to persist when performing (multiple) evaluations of the same circuits using the same model and data set. For instance, the evaluation of mubltiple (different) objective functions.
This class holds only quantities that do not depend on the contained model’s parameters. See
EvaluatedObjectiveFunction
for a class (TODO??) that holds the values of an objective function at a certain parameterspace point. property opBasis
 num_data_params()
The number of degrees of freedom in the data used by this objective function.
Returns
int
 add_omitted_freqs(printer=None, force=False)
Detect omitted frequences (assumed to be 0) so we can compute objective fn correctly
 add_count_vectors(force=False)
Ensure this store contains count and totalcount vectors.
 class pygsti.objectivefns.objectivefns.EvaluatedModelDatasetCircuitsStore(mdc_store, verbosity)
Bases:
ModelDatasetCircuitsStore
Additionally holds quantities at a specific modelparameterspace point.
 class pygsti.objectivefns.objectivefns.MDCObjectiveFunction(raw_objfn, mdc_store, verbosity=0)
Bases:
ObjectiveFunction
,EvaluatedModelDatasetCircuitsStore
An objective function whose probabilities and counts are given by a Model and DataSet, respectively.
Instances of this class glue a model, dataset, and circuit list to a “raw” objective function, resulting in an objective function that is a function of modelparameters and contains counts based on a data set.
The model is treated as a function that computes probabilities (as a function of the model’s parameters) for each circuit outcome, and the data set as a function that similarly computes counts (and totalcounts).
Parameters
 raw_objfnRawObjectiveFunction
The raw objective function  specifies how probability and count values are turned into objective function values.
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Attributes
 namestr
The name of this objective function.
 descriptionstr
A description of this objective function.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 property name
Name of this objective function.
 property description
A description of this objective function.
 classmethod create_from(raw_objfn, model, dataset, circuits, resource_alloc=None, verbosity=0, array_types=())
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
For instance, if the objective function is DeltaLogL then this function would multiply objective_function_value by 2, whereas in the case of a chisquared objective function this function just return objective_function_value.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 abstract lsvec(paramvec=None, oob_check=False)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
 oob_checkbool, optional
Whether the objective function should raise an error if it is being evaluated in an “out of bounds” region.
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 abstract dlsvec(paramvec=None)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 terms(paramvec=None)
Compute the terms of the objective function.
The “terms” are the percircuitoutcome values that get summed together to result in the objective function value.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 dterms(paramvec=None)
Compute the jacobian of the terms of the objective function.
The “terms” are the percircuitoutcome values that get summed together to result in the objective function value. Differentiation is with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 percircuit(paramvec=None)
Compute the percircuit contributions to this objective function.
These values collect (sum) together the contributions of the outcomes of a single circuit.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nCircuits,) where nCircuits is the number of circuits (specified when this objective function was constructed).
 dpercircuit(paramvec=None)
Compute the jacobian of the percircuit contributions of this objective function.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nCircuits, nParams) where nCircuits is the number of circuits and nParams is the number of model parameters (the circuits and model were specified when this objective function was constructed).
 lsvec_percircuit(paramvec=None)
Compute the square root of percircuit contributions to this objective function.
These values are primarily useful for interfacing with a leastsquares optimizer.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nCircuits,) where nCircuits is the number of circuits (specified when this objective function was constructed).
 dlsvec_percircuit(paramvec=None)
Compute the jacobian of the sqrt(percircuit) values given by
lsvec_percircuit()
.This jacobian is primarily useful for interfacing with a leastsquares optimizer.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nCircuits, nParams) where nCircuits is the number of circuits and nParams is the number of model parameters (the circuits and model were specified when this objective function was constructed).
 fn_local(paramvec=None)
Evaluate the local value of this objective function.
When the objective function’s layout is distributed, each processor only holds a portion of the objective function terms, and this function returns only the sum of these local terms. See
fn()
for the global objective function value.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
float
 fn(paramvec=None)
Evaluate the value of this objective function.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
float
 jacobian(paramvec=None)
Compute the Jacobian of this objective function.
Derivatives are takes with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nParams,) where nParams is the number of model parameters.
 abstract hessian(paramvec=None)
Compute the Hessian of this objective function.
Derivatives are takes with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nParams, nParams) where nParams is the number of model parameters.
 abstract approximate_hessian(paramvec=None)
Compute an approximate Hessian of this objective function.
This is typically much less expensive than
hessian()
and does not require that enable_hessian=True was set upon initialization. It computes an approximation to the Hessian that only utilizes the information in the Jacobian. Derivatives are takes with respect to model parameters.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nParams, nParams) where nParams is the number of model parameters.
 class pygsti.objectivefns.objectivefns.RawChi2Function(regularization=None, resource_alloc=None, name='chi2', description='Sum of Chi^2', verbosity=0)
Bases:
RawObjectiveFunction
The function N(pf)^2 / p
Note that this equals Nf (1x)^2 / x where x := p/f.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 set_regularization(min_prob_clip_for_weighting=0.0001)
Set regularization values.
Parameters
 min_prob_clip_for_weightingfloat, optional
Cutoff for probability prob in 1 / prob weighting factor (the maximum of prob and min_prob_clip_for_weighting is used in the denominator).
Returns
None
 lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of sqrt(local_function) at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hterms_alt(probs, counts, total_counts, freqs, intermediates=None)
Alternate computation of the 2nd derivatives of the terms of this objective function.
This should give exactly the same results as
hterms()
, but may be a little faster.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.RawChiAlphaFunction(regularization=None, resource_alloc=None, name='chialpha', description='Sum of ChiAlpha', verbosity=0, alpha=1)
Bases:
RawObjectiveFunction
The function N[x + 1/(alpha * x^alpha)  (1 + 1/alpha)] where x := p/f.
This function interpolates between the loglikelihood function (alpha=>0) and the chi2 function (alpha=1).
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 alphafloat, optional
The alpha parameter, which lies in the interval (0,1].
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 set_regularization(pfratio_stitchpt=0.01, pfratio_derivpt=0.01, radius=None, fmin=None)
Set regularization values.
Parameters
 pfratio_stitchptfloat, optional
The xvalue (x = probility/frequency ratio) below which the function is replaced with it secondorder Taylor expansion.
 pfratio_derivptfloat, optional
The xvalue at which the Taylor expansion derivatives are evaluated at. If this is the same as pfratio_stitchpt then the function is smooth to 2nd order at this point. However, choosing a larger value of pfratio_derivpt will make the stitched part of the function less steep, which is sometimes more helpful to an optimizer than having the stitchpoint be smooth.
 radiusfloat, optional
If radius is not None then a “harsh” method of regularizing the zerofrequency terms (where the local function = N*p) is used. Specifically, for p < radius we splice in the cubic polynomial, (1/3)*p^3/r^2 + p^2/r + (1/3)*r (where r == radius). This has the nice properties that 1) it matches the value, firstderivative, and second derivative of N*p at p=r and 2) it, like N*p has a minimum at p=0 with value 0. The radius dictates the amount of curvature or sharpness of this stitching function, with smaller values making the function more pointed. We recommend making this value smaller than the smallest expected frequencies, so as not to alter the objective function in regions we near the ML point. If radius is None, then fmin is used to handle the zerofrequency terms.
 fminfloat, optional
The minimum expected frequency. When radius is None a “relaxed” regularization of the zerofrequency terms is used that stitches the quadratic N * C * p^2 to N*p when p < 1/C, with C = 1/(2 fmin) * (1 + alpha) / pfratio_derivpt^(2 + alpha). This matches the value of the stitch and N*p at p=1/C but not the derivative, but makes up for this by being less steep  the value of C is chosen so that the derivative (steepness) of the zerofrequency terms at the stitch point is similar to the regular nonzerofrequency terms at their stitch points.
Returns
None
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 abstract hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 abstract hlsvec(probs, counts, total_counts, freqs)
Compute the 2nd derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of sqrt(local_function) at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 class pygsti.objectivefns.objectivefns.RawFreqWeightedChi2Function(regularization=None, resource_alloc=None, name='fwchi2', description='Sum of freqweighted Chi^2', verbosity=0)
Bases:
RawChi2Function
The function N(pf)^2 / f
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 set_regularization(min_freq_clip_for_weighting=0.0001)
Set regularization values.
Parameters
 min_freq_clip_for_weightingfloat, optional
The minimum frequency that will be used in the 1/f weighting factor. That is, the weighting factor is the 1 / max(f, min_freq_clip_for_weighting).
Returns
None
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.RawCustomWeightedChi2Function(regularization=None, resource_alloc=None, name='cwchi2', description='Sum of customweighted Chi^2', verbosity=0, custom_weights=None)
Bases:
RawChi2Function
The function custom_weight^2 (pf)^2, with custom weights that default to 1.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 custom_weightsnumpy.ndarray, optional
Onedimensional array of the custom weights, which linearly multiply the leastsquares terms, i.e. (p  f). If None, then unit weights are used and the objective function computes the sum of unweighted squares.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.RawPoissonPicDeltaLogLFunction(regularization=None, resource_alloc=None, name='dlogl', description='2*Delta(log(L))', verbosity=0)
Bases:
RawObjectiveFunction
The function N*f*log(f/p)  N*(fp).
Note that this equals Nf(log(x)  1 + x) where x := p/f.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 set_regularization(min_prob_clip=0.0001, pfratio_stitchpt=None, pfratio_derivpt=None, radius=0.0001, fmin=None)
Set regularization values.
Parameters
 min_prob_clipfloat, optional
The probability below which the objective function is replaced with its second order Taylor expansion. This must be None if pfratio_stitchpt is not None, this specifies an alternate stitching method where the stitchpoint is given in x=p/f units.
 pfratio_stitchptfloat, optional
The xvalue (x = probility/frequency ratio) below which the function is replaced with it second order Taylor expansion. Conflicts with min_prob_clip, which specifies an alternate stitching method.
 pfratio_derivptfloat, optional
Specified if and only if pfratio_stitchpt is. The xvalue at which the Taylor expansion derivatives are evaluated at. If this is the same as pfratio_stitchpt then the function is smooth to 2nd order at this point. However, choosing a larger value of pfratio_derivpt will make the stitched part of the function less steep, which is sometimes more helpful to an optimizer than having the stitchpoint be smooth.
 radiusfloat, optional
If radius is not None then a “harsh” method of regularizing the zerofrequency terms (where the local function = N*p) is used. Specifically, for p < radius we splice in the cubic polynomial, (1/3)*p^3/r^2 + p^2/r + (1/3)*r (where r == radius). This has the nice properties that 1) it matches the value, firstderivative, and second derivative of N*p at p=r and 2) it, like N*p has a minimum at p=0 with value 0. The radius dictates the amount of curvature or sharpness of this stitching function, with smaller values making the function more pointed. We recommend making this value smaller than the smallest expected frequencies, so as not to alter the objective function in regions we near the ML point. If radius is None, then fmin is used to handle the zerofrequency terms.
 fminfloat, optional
The minimum expected frequency. When radius is None a “relaxed” regularization of the zerofrequency terms is used that stitches the quadratic N * C * p^2 to N*p when p < 1/C, with C = 1/(2 fmin) * (1 + alpha) / pfratio_derivpt^(2 + alpha). This matches the value of the stitch and N*p at p=1/C but not the derivative, but makes up for this by being less steep  the value of C is chosen so that the derivative (steepness) of the zerofrequency terms at the stitch point is similar to the regular nonzerofrequency terms at their stitch points.
Returns
None
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 class pygsti.objectivefns.objectivefns.RawDeltaLogLFunction(regularization=None, resource_alloc=None, name='dlogl', description='2*Delta(log(L))', verbosity=0)
Bases:
RawObjectiveFunction
The function N*f*log(f/p).
Note that this equals Nf log(x) where x := p/f.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 set_regularization(min_prob_clip=0.0001, pfratio_stitchpt=None, pfratio_derivpt=None)
Set regularization values.
Parameters
 min_prob_clipfloat, optional
The probability below which the objective function is replaced with its second order Taylor expansion. This must be None if pfratio_stitchpt is not None, this specifies an alternate stitching method where the stitchpoint is given in x=p/f units.
 pfratio_stitchptfloat, optional
The xvalue (x = probility/frequency ratio) below which the function is replaced with it second order Taylor expansion. Conflicts with min_prob_clip, which specifies an alternate stitching method.
 pfratio_derivptfloat, optional
Specified if and only if pfratio_stitchpt is. The xvalue at which the Taylor expansion derivatives are evaluated at. If this is the same as pfratio_stitchpt then the function is smooth to 2nd order at this point. However, choosing a larger value of pfratio_derivpt will make the stitched part of the function less steep, which is sometimes more helpful to an optimizer than having the stitchpoint be smooth.
Returns
None
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec_and_lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the leastsquares vector together with the vector itself.
This is sometimes more computationally efficient than calling
dlsvec()
andlsvec()
separately, as the former call may require computing the latter.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 dlsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 hlsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of sqrt(local_function) at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.RawMaxLogLFunction(regularization=None, resource_alloc=None, name='maxlogl', description='Max LogL', verbosity=0, poisson_picture=True)
Bases:
RawObjectiveFunction
The function N*f*log(f) (note this doesn’t depend on the probability!).
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec(probs, counts, total_counts, freqs, intermediates=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec(probs, counts, total_counts, freqs)
Compute the derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 dlsvec_and_lsvec(probs, counts, total_counts, freqs)
Compute the derivatives of the leastsquares vector together with the vector itself.
This is sometimes more computationally efficient than calling
dlsvec()
andlsvec()
separately, as the former call may require computing the latter.Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 dlsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 lsvec: numpy.ndarray
A 1D array of length equal to that of each array argument.
 hlsvec(probs, counts, total_counts, freqs)
Compute the 2nd derivatives of the leastsquares vector of this objective function.
Note that because each lsvec element only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of sqrt(local_function) at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.RawTVDFunction(regularization=None, resource_alloc=None, name='tvd', description='Total Variational Distance (TVD)', verbosity=0)
Bases:
RawObjectiveFunction
The function 0.5 * pf.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
Create a raw objective function.
A raw objective function acts on “raw” probabilities and counts, and is usually a statistic comparing the probabilities to count data.
Parameters
 regularizationdict, optional
Regularization values.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 terms(probs, counts, total_counts, freqs, intermediates=None)
Compute the terms of the objective function.
The “terms” are the per(probability, count, totalcount) values that get summed together to result in the objective function value. These are the “local” or “perelement” values of the objective function.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 abstract dterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise derivative (or, the diagonal of a jacobian matrix), i.e. the resulting values are the derivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 abstract hterms(probs, counts, total_counts, freqs, intermediates=None)
Compute the 2nd derivatives of the terms of this objective function.
Note that because each term only depends on the corresponding probability, this is just an elementwise 2nd derivative, i.e. the resulting values are the 2ndderivatives of the local_function at each (probability, count, totalcount) value.
Parameters
 probsnumpy.ndarray
Array of probability values.
 countsnumpy.ndarray
Array of count values.
 total_countsnumpy.ndarray
Array of total count values.
 freqsnumpy.ndarray
Array of frequency values. This should always equal counts / total_counts but is supplied separately to increase performance.
 intermediatestuple, optional
Used internally to speed up computations.
Returns
 numpy.ndarray
A 1D array of length equal to that of each array argument.
 zero_freq_terms(total_counts, probs)
Evaluate objective function terms with zero frequency (where count and frequency are zero).
Such terms are treated specially because, for some objective functions, having zero frequency is a special case and must be handled differently.
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 abstract zero_freq_dterms(total_counts, probs)
Evaluate the derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 abstract zero_freq_hterms(total_counts, probs)
Evaluate the 2nd derivative of zerofrequency objective function terms.
Zero frequency terms are treated specially because, for some objective functions, these are a special case and must be handled differently. Derivatives are evaluated elementwise, i.e. the ith element of the returned array is the 2nd derivative of the ith term with respect to the ith probability (derivatives with respect to all other probabilities are zero because of the function structure).
Parameters
 total_countsnumpy.ndarray
The total counts.
 probsnumpy.ndarray
The probabilities.
Returns
 numpy.ndarray
A 1D array of the same length as total_counts and probs.
 class pygsti.objectivefns.objectivefns.TimeIndependentMDCObjectiveFunction(raw_objfn, mdc_store, penalties=None, verbosity=0)
Bases:
MDCObjectiveFunction
A timeindependent modelbased (
MDCObjectiveFunction
derived) objective function.Parameters
 raw_objfnRawObjectiveFunction
The raw objective function  specifies how probability and count values are turned into objective function values.
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod builder(name=None, description=None, regularization=None, penalties=None, **kwargs)
Create an
ObjectiveFunctionBuilder
that builds an objective function of this type.Parameters
 namestr, optional
A name for the built objective function (can be anything).
 descriptionstr, optional
A description for the built objective function (can be anything)
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values.
Returns
ObjectiveFunctionBuilder
 classmethod create_from(raw_objfn, model, dataset, circuits, resource_alloc=None, penalties=None, verbosity=0, method_names=('fn',), array_types=())
 classmethod compute_array_types(method_names, fsim)
 set_penalties(regularize_factor=0, cptp_penalty_factor=0, spam_penalty_factor=0, errorgen_penalty_factor=0, forcefn_grad=None, shift_fctr=100, prob_clip_interval=(10000, 1000))
Set penalty terms.
Parameters
 regularize_factorfloat, optional
The prefactor of a L1 regularization term that penalizes parameter vector elements that exceed an absolute value of 1.0. Adds a penalty term: regularize_factor * max(0, parameter_value  1.0) for each model parameter.
 cptp_penalty_factorfloat, optional
The prefactor of a term that penalizes nonCPTP operations. Specifically, adds a cptp_penalty_factor * sqrt(tracenorm(choi_matrix)) penalty utilizing each operation’s (gate’s) Choi matrix.
 spam_penalty_factorfloat, optional
The prefactor of a term that penalizes invalid SPAM operations. Specifically, adds a spam_penalty_factor * sqrt(tracenorm(spam_op)) penalty where spam_op runs over each state preparation’s density matrix and each effect vector’s matrix.
 errorgen_penalty_factorfloat, optional
The prefactor of a term that penalizes nonzero error generators. Specifically, adds a errorgen_penalty_factor * sqrt(sum_i(errorgen_coeff_i)) penalty where the sum ranges over all the error generator coefficients of each model operation.
 forcefn_gradnumpy.ndarray, optional
The gradient of a “forcing function” that is added to the objective function. This is used in the calculation of linearresponse error bars.
 shift_fctrfloat, optional
An adjustment prefactor for computing the “shift” that serves as a constant offset of the forcing function, i.e. the forcing function (added to the objective function) is essentially ForceFn = force_shift + dot(forcefn_grad, parameter_vector), and force_shift = shift_fctr * forcefn_grad * (forcefn_grad + parameter_vector). Here  indicates a frobenius norm. The idea behind all this is that ForceFn as given above must remain positive (for leastsquares optimization), and so shift_fctr must be large enough to ensure this is the case. Usually you don’t need to alter the default value.
 prob_clip_intervaltuple, optional
A (min, max) tuple that specifies the minium (possibly negative) and maximum values allowed for probabilities generated by the model. If the model gives probabilities outside this range they are clipped to min or max. These values can be quite generous, as the optimizers are quite tolerant of badly behaved probabilities.
Returns
 int
The number of penalty terms.
 lsvec(paramvec=None, oob_check=False)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
 oob_checkbool, optional
Whether the objective function should raise an error if it is being evaluated in an “out of bounds” region.
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 terms(paramvec=None)
Compute the terms of the objective function.
The “terms” are the percircuitoutcome values that get summed together to result in the objective function value.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 dlsvec(paramvec=None)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 dterms(paramvec=None)
Compute the jacobian of the terms of the objective function.
The “terms” are the percircuitoutcome values that get summed together to result in the objective function value. Differentiation is with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 hessian_brute(paramvec=None)
Computes the Hessian using a brute force approach.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
The hessian of this objective function, of shape (N,N) where N is the number of model parameters.
 approximate_hessian(paramvec=None)
Compute an approximate Hessian of this objective function.
This is typically much less expensive than
hessian()
and does not require that enable_hessian=True was set upon initialization. It computes an approximation to the Hessian that only utilizes the information in the Jacobian. Derivatives are takes with respect to model parameters.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nParams, nParams) where nParams is the number of model parameters.
 hessian(paramvec=None)
Compute the Hessian of this objective function.
Derivatives are takes with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nParams, nParams) where nParams is the number of model parameters.
 class pygsti.objectivefns.objectivefns.Chi2Function(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased chisquared function: N(pf)^2 / p
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 class pygsti.objectivefns.objectivefns.ChiAlphaFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0, alpha=1)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased chialpha function: N[x + 1/(alpha * x^alpha)  (1 + 1/alpha)] where x := p/f.
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
 alphafloat, optional
The alpha parameter, which lies in the interval (0,1].
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=(), alpha=1)
 class pygsti.objectivefns.objectivefns.FreqWeightedChi2Function(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased frequencyweighted chisquared function: N(pf)^2 / f
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 class pygsti.objectivefns.objectivefns.CustomWeightedChi2Function(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0, custom_weights=None)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased customweighted chisquared function: cw^2 (pf)^2
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
 custom_weightsnumpy.ndarray, optional
Onedimensional array of the custom weights, which linearly multiply the leastsquares terms, i.e. (p  f). If None, then unit weights are used and the objective function computes the sum of unweighted squares.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=(), custom_weights=None)
 class pygsti.objectivefns.objectivefns.PoissonPicDeltaLogLFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased poissonpicture delta loglikelihood function: N*f*log(f/p)  N*(fp).
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 class pygsti.objectivefns.objectivefns.DeltaLogLFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased delta loglikelihood function: N*f*log(f/p).
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 class pygsti.objectivefns.objectivefns.MaxLogLFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0, poisson_picture=True)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased maximummodel loglikelihood function: N*f*log(f)
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=(), poisson_picture=True)
 class pygsti.objectivefns.objectivefns.TVDFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeIndependentMDCObjectiveFunction
Modelbased TVD function: 0.5 * pf.
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 descriptionstr, optional
A description for this objective function (can be anything)
 verbosityint, optional
Level of detail to print to stdout.
 enable_hessianbool, optional
Whether hessian calculations are allowed. If True then more resources are needed. If False, calls to hessianrequiring function will result in an error.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 class pygsti.objectivefns.objectivefns.TimeDependentMDCObjectiveFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
MDCObjectiveFunction
A timedependent modelbased objective function
Parameters
 mdlModel
The model  specifies how parameter values are turned into probabilities for each circuit outcome.
 datasetDataSet
The data set  specifies how counts and total_counts are obtained for each circuit outcome.
 circuitslist or CircuitList
The circuit list  specifies what probabilities and counts this objective function compares. If None, then the keys of dataset are used.
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values. Penalties usually add additional (penalty) terms to the sum of percircuitoutcome contributions that evaluate to the objective function.
 resource_allocResourceAllocation, optional
Available resources and how they should be allocated for computations.
 namestr, optional
A name for this objective function (can be anything).
 verbosityint, optional
Level of detail to print to stdout.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 classmethod builder(name=None, description=None, regularization=None, penalties=None, **kwargs)
Create an
ObjectiveFunctionBuilder
that builds an objective function of this type.Parameters
 namestr, optional
A name for the built objective function (can be anything).
 descriptionstr, optional
A description for the built objective function (can be anything)
 regularizationdict, optional
Regularization values.
 penaltiesdict, optional
Penalty values.
Returns
ObjectiveFunctionBuilder
 classmethod create_from(model, dataset, circuits, regularization=None, penalties=None, resource_alloc=None, name=None, description=None, verbosity=0, method_names=('fn',), array_types=())
 classmethod compute_array_types(method_names, fsim)
 set_penalties()
Set penalty terms.
 abstract lsvec(paramvec=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 abstract dlsvec(paramvec=None)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 class pygsti.objectivefns.objectivefns.TimeDependentChi2Function(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeDependentMDCObjectiveFunction
Chisquared function that can handle timedependent circuits and data.
This objective function can handle timedependent circuits  that is, circuits are treated as potentially timedependent and mdl as well. This function currently doesn’t support much regularization or penalization.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 set_regularization(min_prob_clip_for_weighting=0.0001, radius=0.0001)
Set regularization values.
Parameters
 min_prob_clip_for_weightingfloat, optional
Cutoff for probability prob in 1 / prob weighting factor (the maximum of prob and min_prob_clip_for_weighting is used in the denominator).
 radiusfloat, optional
Affects sharpness of the regularization of zerofrequency terms.
Returns
None
 set_penalties(regularize_factor=0, cptp_penalty_factor=0, spam_penalty_factor=0, errorgen_penalty_factor=0, prob_clip_interval=(10000, 10000))
Set penalty terms.
Parameters
 regularize_factorfloat, optional
The prefactor of a L1 regularization term that penalizes parameter vector elements that exceed an absolute value of 1.0. Adds a penalty term: regularize_factor * max(0, parameter_value  1.0) for each model parameter.
 cptp_penalty_factorfloat, optional
The prefactor of a term that penalizes nonCPTP operations. Specifically, adds a cptp_penalty_factor * sqrt(tracenorm(choi_matrix)) penalty utilizing each operation’s (gate’s) Choi matrix.
 spam_penalty_factorfloat, optional
The prefactor of a term that penalizes invalid SPAM operations. Specifically, adds a spam_penalty_factor * sqrt(tracenorm(spam_op)) penalty where spam_op runs over each state preparation’s density matrix and each effect vector’s matrix.
 errorgen_penalty_factorfloat, optional
The prefactor of a term that penalizes nonzero error generators. Specifically, adds a errorgen_penalty_factor * sqrt(sum_i(errorgen_coeff_i)) penalty where the sum ranges over all the error generator coefficients of each model operation.
 prob_clip_intervaltuple, optional
A (min, max) tuple that specifies the minium (possibly negative) and maximum values allowed for probabilities generated by the model. If the model gives probabilities outside this range they are clipped to min or max. These values can be quite generous, as the optimizers are quite tolerant of badly behaved probabilities.
Returns
 int
The number of penalty terms.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 lsvec(paramvec=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 dlsvec(paramvec=None)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 class pygsti.objectivefns.objectivefns.TimeDependentPoissonPicLogLFunction(mdc_store, regularization=None, penalties=None, name=None, description=None, verbosity=0)
Bases:
TimeDependentMDCObjectiveFunction
Poissonpicture delta loglikelihood function that can handle timedependent circuits and data.
This objective function can handle timedependent circuits  that is, circuits are treated as potentially timedependent and mdl as well. This function currently doesn’t support much regularization or penalization.
Create a new MDCObjectiveFunction.
mdc_store is thought to be a normal MDC store, but could also be an evaluated one, in which case should we take enable_hessian from it?
 set_regularization(min_prob_clip=0.0001, radius=0.0001)
Set regularization values.
Parameters
 min_prob_clipfloat, optional
The probability below which the objective function is replaced with its second order Taylor expansion.
 radiusfloat, optional
Affects sharpness of the regularization of zerofrequency terms.
Returns
None
 set_penalties(cptp_penalty_factor=0, spam_penalty_factor=0, errorgen_penalty_factor=0, forcefn_grad=None, shift_fctr=100, prob_clip_interval=(10000, 10000))
Set penalties.
Parameters
 cptp_penalty_factorfloat, optional
The prefactor of a term that penalizes nonCPTP operations. Specifically, adds a cptp_penalty_factor * sqrt(tracenorm(choi_matrix)) penalty utilizing each operation’s (gate’s) Choi matrix.
 spam_penalty_factorfloat, optional
The prefactor of a term that penalizes invalid SPAM operations. Specifically, adds a spam_penalty_factor * sqrt(tracenorm(spam_op)) penalty where spam_op runs over each state preparation’s density matrix and each effect vector’s matrix.
 errorgen_penalty_factorfloat, optional
The prefactor of a term that penalizes nonzero error generators. Specifically, adds a errorgen_penalty_factor * sqrt(sum_i(errorgen_coeff_i)) penalty where the sum ranges over all the error generator coefficients of each model operation.
 forcefn_gradnumpy.ndarray, optional
The gradient of a “forcing function” that is added to the objective function. This is used in the calculation of linearresponse error bars.
 shift_fctrfloat, optional
An adjustment prefactor for computing the “shift” that serves as a constant offset of the forcing function, i.e. the forcing function (added to the objective function) is essentially ForceFn = force_shift + dot(forcefn_grad, parameter_vector), and force_shift = shift_fctr * forcefn_grad * (forcefn_grad + parameter_vector). Here  indicates a frobenius norm. The idea behind all this is that ForceFn as given above must remain positive (for leastsquares optimization), and so shift_fctr must be large enough to ensure this is the case. Usually you don’t need to alter the default value.
 prob_clip_intervaltuple, optional
A (min, max) tuple that specifies the minium (possibly negative) and maximum values allowed for probabilities generated by the model. If the model gives probabilities outside this range they are clipped to min or max. These values can be quite generous, as the optimizers are quite tolerant of badly behaved probabilities.
Returns
 int
The number of penalty terms.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 lsvec(paramvec=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 dlsvec(paramvec=None)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to model parameters.
Parameters
 paramvecnumpy.ndarray, optional
The vector of (model) parameters to evaluate the objective function at. If None, then the model’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of model parameters.
 class pygsti.objectivefns.objectivefns.LogLWildcardFunction(logl_objective_fn, base_pt, wildcard)
Bases:
ObjectiveFunction
A wildcardbudget bolton to an existing objective function.
Currently, this existing function must be a loglikelihood type function because the computational logic assumes this. The resulting object is an objective function over the space of wildcard budget parameter vectors (not model parameters).
Parameters
 logl_objective_fnPoissonPicDeltaLogLFunction
The bare loglikelihood function.
 base_ptnumpy.ndarray
Unused. The modelparamter vector where this objective function is based.
 wildcardWildcardBudget
The wildcard budget that adjusts the “bare” probabilities of logl_objective_fn before evaluating the rest of the objective function.
 chi2k_distributed_qty(objective_function_value)
Convert a value of this objective function to one that is expected to be chi2_k distributed.
Parameters
 objective_function_valuefloat
A value of this objective function, i.e. one returned from self.fn(…).
Returns
float
 fn(wvec=None)
Evaluate this objective function.
Parameters
 wvecnumpy.ndarray, optional
The vector of (wildcard budget) parameters to evaluate the objective function at. If None, then the budget’s current parameter vector is used (held internally).
Returns
float
 terms(wvec=None)
Compute the terms of the objective function.
The “terms” are the percircuitoutcome values that get summed together to result in the objective function value.
Parameters
 wvecnumpy.ndarray, optional
The vector of (wildcard budget) parameters to evaluate the objective function at. If None, then the budget’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 lsvec(wvec=None)
Compute the leastsquares vector of the objective function.
This is the squareroot of the termsvector returned from
terms()
. This vector is the objective function value used by a leastsquares optimizer when optimizing this objective function. Note that the existence of this quantity requires that the terms be nonnegative. If this is not the case, an error is raised.Parameters
 wvecnumpy.ndarray, optional
The vector of (wildcard budget) parameters to evaluate the objective function at. If None, then the budget’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,) where nElements is the number of circuit outcomes.
 abstract dlsvec(wvec)
The derivative (jacobian) of the leastsquares vector.
Derivatives are taken with respect to wildcard budget parameters.
Parameters
 wvecnumpy.ndarray, optional
The vector of (wildcard budget) parameters to evaluate the objective function at. If None, then the budget’s current parameter vector is used (held internally).
Returns
 numpy.ndarray
An array of shape (nElements,nParams) where nElements is the number of circuit outcomes and nParams is the number of wildcard budget parameters.
 class pygsti.objectivefns.objectivefns.CachedObjectiveFunction(objective_function)
Bases:
pygsti.baseobjs.nicelyserializable.NicelySerializable
Holds various values of an objective function at a particular point.
This object is meant to be serializable, and not to facilitate computing the objective function anywhere else. It doesn’t contain or rely on comm objects. It does contain a serial or “global” layout that allows us to make sense of the elements of various probability vectors, etc., but we demand that this layout not depend on comm objects.
The cache may only have values on the rank0 proc (??)
 collection_name = "'pygsti_cached_objective_fns'"
 classmethod from_dir(dirname, quick_load=False)
Initialize a new CachedObjectiveFunction object from dirname.
 quick_loadbool, optional
Setting this to True skips the loading of components that may take a long time to load.
Parameters
 dirnamestr
The directory name.
 quick_loadbool, optional
Setting this to True skips the loading of components that may take a long time to load.
Returns
CachedObjectiveFunction