dcnum.os_env_st
===============

.. py:module:: dcnum.os_env_st


Attributes
----------

.. autoapisummary::

   dcnum.os_env_st.os_env_threading


Classes
-------

.. autoapisummary::

   dcnum.os_env_st.RequestSingleThreaded


Functions
---------

.. autoapisummary::

   dcnum.os_env_st.confirm_single_threaded
   dcnum.os_env_st.request_single_threaded


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

.. py:data:: os_env_threading
   :value: ['MKL_NUM_THREADS', 'NUMBA_NUM_THREADS', 'NUMEXPR_NUM_THREADS', 'NUMPY_NUM_THREADS',...


   environment variables that define number of threads libraries will use

.. py:class:: RequestSingleThreaded

   Context manager for starting a process with specific environment

   When entering the context, the environment variables defined in
   ``os_env_threading`` are all set to "1", telling the relevant libraries
   that they should work in single-threaded mode.
   When exiting the context, these environment variables are reset to
   their original values (or unset if applicable).

   Note that it makes only sense to use this context manager when
   starting new multiprocessing processes. When the process spawns,
   the environment from the current thread is copied. Setting the
   environment variable after e.g. importing numpy has no effect
   on how many threads numpy will use.


   .. py:attribute:: previous_env


   .. py:method:: __enter__()

      Ask nicely for single-threaded computation using `os.environ`

      Note that this only affects new processes in which the
      relevant libraries have not yet been imported.



   .. py:method:: __exit__(type, value, traceback)

      Restore the previous environment



.. py:function:: confirm_single_threaded()

   Warn via logs when environment variables are not set to single thread


.. py:function:: request_single_threaded()

   Set the environment variable to single thread

   This function must be called before importing the multithreaded
   libraries (such as numpy) in order for them to pick up the
   environment variables.