:py:mod:`pygsti.algorithms.contract`
====================================

.. py:module:: pygsti.algorithms.contract

.. autoapi-nested-parse::

   GST contraction algorithms






Module Contents
---------------


Functions
~~~~~~~~~

.. autoapisummary::

   pygsti.algorithms.contract.contract



.. py:function:: contract(model, to_what, dataset=None, maxiter=1000000, tol=0.01, use_direct_cp=True, method='Nelder-Mead', verbosity=0)

   Contract a Model to a specified space.

   All contraction operations except 'vSPAM' operate entirely on the gate
   matrices and leave state preparations and measurments alone, while 'vSPAM'
   operations only on SPAM.

   Parameters
   ----------
   model : Model
       The model to contract

   to_what : string
       Specifies which space is the model is contracted to.
       Allowed values are:

       - 'TP'     -- All gates are manifestly trace-preserving maps.
       - 'CP'     -- All gates are manifestly completely-positive maps.
       - 'CPTP'   -- All gates are manifestly completely-positive and trace-preserving maps.
       - 'XP'     -- All gates are manifestly "experimentally-positive" maps.
       - 'XPTP'   -- All gates are manifestly "experimentally-positive" and trace-preserving maps.
       - 'vSPAM'  -- state preparation and measurement operations are valid.
       - 'nothing' -- no contraction is performed.

   dataset : DataSet, optional
       Dataset to use to determine whether a model is in the
       "experimentally-positive" (XP) space.  Required only when
       contracting to XP or XPTP.

   maxiter : int, optional
       Maximum number of iterations for iterative contraction routines.

   tol : float, optional
       Tolerance for iterative contraction routines.

   use_direct_cp : bool, optional
       Whether to use a faster direct-contraction method for CP
       contraction.  This method essentially transforms to the
       Choi matrix, truncates any negative eigenvalues to zero,
       then transforms back to a operation matrix.

   method : string, optional
       The method used when contracting to XP and non-directly to CP
       (i.e. use_direct_cp == False).

   verbosity : int, optional
       How much detail to send to stdout.

   Returns
   -------
   Model
       The contracted model