mpi4py

The MPI for Python package.

The Message Passing Interface (MPI) is a standardized and portable message-passing system designed to function on a wide variety of parallel computers. The MPI standard defines the syntax and semantics of library routines and allows users to write portable programs in the main scientific programming languages (Fortran, C, or C++). Since its release, the MPI specification has become the leading standard for message-passing libraries for parallel computers.

MPI for Python provides MPI bindings for the Python programming language, allowing any Python program to exploit multiple processors. This package build on the MPI specification and provides an object oriented interface which closely follows MPI-2 C++ bindings.

Runtime configuration options

mpi4py.rc: This object has attributes exposing runtime configuration options that become effective at import time of the MPI module.

Attributes Summary

`initialize`	Automatic MPI initialization at import
`threads`	Request initialization with thread support
`thread_level`	Level of thread support to request
`finalize`	Automatic MPI finalization at exit
`fast_reduce`	Use tree-based reductions for objects
`recv_mprobe`	Use matched probes to receive objects
`irecv_bufsz`	Default buffer size in bytes for `irecv()`
`errors`	Error handling policy

Attributes Documentation

mpi4py.rc.initialize

Automatic MPI initialization at import.

Type:: bool
Default:: True

See also

MPI4PY_RC_INITIALIZE

mpi4py.rc.threads

Request initialization with thread support.

Type:: bool
Default:: True

See also

MPI4PY_RC_THREADS

mpi4py.rc.thread_level

Level of thread support to request.

Type:: str
Default:: "multiple"
Choices:: "multiple", "serialized", "funneled", "single"

See also

MPI4PY_RC_THREAD_LEVEL

mpi4py.rc.finalize

Automatic MPI finalization at exit.

Type:: None or bool
Default:: None

See also

MPI4PY_RC_FINALIZE

mpi4py.rc.fast_reduce

Use tree-based reductions for objects.

Type:: bool
Default:: True

See also

MPI4PY_RC_FAST_REDUCE

mpi4py.rc.recv_mprobe

Use matched probes to receive objects.

Type:: bool
Default:: True

See also

MPI4PY_RC_RECV_MPROBE

mpi4py.rc.irecv_bufsz

Default buffer size in bytes for irecv().

Type:: int
Default:: 32768

See also

MPI4PY_RC_IRECV_BUFSZ

New in version 4.0.0.

mpi4py.rc.errors

Error handling policy.

Type:: str
Default:: "exception"
Choices:: "exception", "default", "abort", "fatal"

See also

MPI4PY_RC_ERRORS

Example

MPI for Python features automatic initialization and finalization of the MPI execution environment. By using the mpi4py.rc object, MPI initialization and finalization can be handled programmatically:

import mpi4py
mpi4py.rc.initialize = False  # do not initialize MPI automatically
mpi4py.rc.finalize = False    # do not finalize MPI automatically

from mpi4py import MPI # import the 'MPI' module

MPI.Init()      # manual initialization of the MPI environment
...             # your finest code here ...
MPI.Finalize()  # manual finalization of the MPI environment

Environment variables

The following environment variables override the corresponding attributes of the mpi4py.rc and MPI.pickle objects at import time of the MPI module.

Note

For variables of boolean type, accepted values are 0 and 1 (interpreted as False and True, respectively), and strings specifying a YAML boolean value (case-insensitive).

MPI4PY_RC_INITIALIZE

Type:: bool
Default:: True

Whether to automatically initialize MPI at import time of the mpi4py.MPI module.

See also

mpi4py.rc.initialize

New in version 4.0.0.

MPI4PY_RC_FINALIZE

Type:: None | bool
Default:: None
Choices:: None, True, False

Whether to automatically finalize MPI at exit time of the Python process.

See also

mpi4py.rc.finalize

New in version 4.0.0.

MPI4PY_RC_THREADS

Type:: bool
Default:: True

Whether to initialize MPI with thread support.

See also

mpi4py.rc.threads

New in version 3.1.0.

MPI4PY_RC_THREAD_LEVEL

Default:: "multiple"
Choices:: "single", "funneled", "serialized", "multiple"

The level of required thread support.

See also

mpi4py.rc.thread_level

New in version 3.1.0.

MPI4PY_RC_FAST_REDUCE

Type:: bool
Default:: True

Whether to use tree-based reductions for objects.

See also

mpi4py.rc.fast_reduce

New in version 3.1.0.

MPI4PY_RC_RECV_MPROBE

Type:: bool
Default:: True

Whether to use matched probes to receive objects.

See also

mpi4py.rc.recv_mprobe

MPI4PY_RC_IRECV_BUFSZ

Type:: bool
Default:: True

Default buffer size in bytes for irecv().

See also

mpi4py.rc.irecv_bufsz

New in version 4.0.0.

MPI4PY_RC_ERRORS

Default:: "exception"
Choices:: "exception", "default", "abort", "fatal"

Controls default MPI error handling policy.

See also

mpi4py.rc.errors

New in version 3.1.0.

MPI4PY_PICKLE_PROTOCOL

Type:: int
Default:: pickle.HIGHEST_PROTOCOL

Controls the default pickle protocol to use when communicating Python objects.

See also

PROTOCOL attribute of the MPI.pickle object within the MPI module.

New in version 3.1.0.

MPI4PY_PICKLE_THRESHOLD

Type:: int
Default:: 262144

Controls the default buffer size threshold for switching from in-band to out-of-band buffer handling when using pickle protocol version 5 or higher.

See also

THRESHOLD attribute of the MPI.pickle object within the MPI module.

New in version 3.1.2.

Miscellaneous functions

mpi4py.profile(name, *, path=None)

Support for the MPI profiling interface.

Parameters:

name (str) – Name of the profiler library to load.
path (sequence of str, optional) – Additional paths to search for the profiler.

Return type:

None

mpi4py.get_include()

Return the directory in the package that contains header files.

Extension modules that need to compile against mpi4py should use this function to locate the appropriate include directory. Using Python distutils (or perhaps NumPy distutils):

import mpi4py
Extension('extension_name', ...
          include_dirs=[..., mpi4py.get_include()])

Return type:: str

mpi4py.get_config()

Return a dictionary with information about MPI.

Changed in version 4.0.0: By default, this function returns an empty dictionary. However, downstream packagers and distributors may alter such behavior. To that end, MPI information must be provided under an mpi section within a UTF-8 encoded INI-style configuration file mpi.cfg located at the top-level package directory. The configuration file is read and parsed using the configparser module.

Return type:: dict[str, str]