jexplore.steps.stretch
======================

.. py:module:: jexplore.steps.stretch

.. autoapi-nested-parse::

   This module define the class for a MH step based on stretch proposal.



Classes
-------

.. autoapisummary::

   jexplore.steps.stretch.Stretch


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

.. py:class:: Stretch[Tepoch: jexplore.sampling.EpochMH, Tstate: jexplore.sampling.StateMH, Tsampling: jexplore.sampling.SamplingMH](a = 2.0, ngroups = 2, permute = False)

   Bases: :py:obj:`jexplore.steps.colored.ColoredSC`\ [\ :py:obj:`Tepoch`\ , :py:obj:`Tstate`\ , :py:obj:`Tsampling`\ ]


   Class implementing a MH steps based on stretch proposal

   :param a: stretch proposal `a` parameter
   :param ngroups: number of groups. Default 2.
   :param permute: if true walkers are permuted at each iteration.


   .. py:attribute:: npart
      :type:  int
      :value: 1


      number of partners needed to build the proposal


   .. py:attribute:: a
      :type:  float

      stretch proposal `a` parameter


   .. py:attribute:: sa


   .. py:method:: sample_z(key, size)

      Sample the z distribution

      :param key: PRNG key
      :param size: output size

      :return: samples



   .. py:method:: proposal(key, state, group, cgroup)

      Propose a new state according to the stretch proposal algorithm.

      :param key: PRNG key
      :param state: current state
      :param group: indexes of the color chains
      :param cgroup: indexes of the complementary chains for this color.

      :return: new state and the boolean mask of the chains modified by the step.