Mpi4py

==========================

* Bug fixes:

+ Fix handling of readonly buffers in support for Python 2 legacy
buffer interface. The issue triggers only when using a buffer-like
object that is readonly and does not export the new Python 3
buffer interface.
+ Fix build issues with Open MPI 4.0.x series related to removal of
many MPI-1 symbols deprecated in MPI-2 and removed in MPI-3.
+ Minor documentation fixes.

==========================

* Bug fixes:

+ Fix ``Comm.scatter()`` and other collectives corrupting input send
list. Add safety measures to prevent related issues in global
reduction operations.
+ Fix error-checking code for counts in ``Op.Reduce_local()``.

* Enhancements:

+ Map size-specific Python/NumPy typecodes to MPI datatypes.
+ Allow partial specification of target list/tuple arguments in the
various ``Win`` RMA methods.
+ Workaround for removal of ``MPI_{LB|UB}`` in Open MPI 4.0.
+ Support for Microsoft MPI v10.0.

==========================

* New features:

+ `mpi4py.futures`: Execute computations asynchronously using a pool
of MPI processes. This package is based on ``concurrent.futures``
from the Python standard library.
+ `mpi4py.run`: Run Python code and abort execution in case of
unhandled exceptions to prevent deadlocks.
+ `mpi4py.bench`: Run basic MPI benchmarks and tests.

* Enhancements:

+ Lowercase, pickle-based collective communication calls are now
thread-safe through the use of fine-grained locking.
+ The ``MPI`` module now exposes a ``memory`` type which is a
lightweight variant of the builtin ``memoryview`` type, but
exposes both the legacy Python 2 and the modern Python 3 buffer
interface under a Python 2 runtime.
+ The ``MPI.Comm.Alltoallw()`` method now uses ``count=1`` and
``displ=0`` as defaults, assuming that messages are specified
through user-defined datatypes.
+ The ``Request.Wait[all]()`` methods now return ``True`` to match
the interface of ``Request.Test[all]()``.
+ The ``Win`` class now implements the Python buffer interface.

* Backward-incompatible changes:

+ The ``buf`` argument of the ``MPI.Comm.recv()`` method is
deprecated, passing anything but ``None`` emits a warning.
+ The ``MPI.Win.memory`` property was removed, use the
``MPI.Win.tomemory()`` method instead.
+ Executing ``python -m mpi4py`` in the command line is now
equivalent to ``python -m mpi4py.run``. For the former behavior,
use ``python -m mpi4py.bench``.
+ Python 2.6 and 3.2 are no longer supported. The ``mpi4py.MPI``
module may still build and partially work, but other pure-Python
modules under the ``mpi4py`` namespace will not.
+ Windows: Remove support for legacy MPICH2, Open MPI, and DeinoMPI.

==========================

* Support for MPI-3 features.

+ Matched probes and receives.
+ Nonblocking collectives.
+ Neighborhood collectives.
+ New communicator constructors.
+ Request-based RMA operations.
+ New RMA communication and synchronisation calls.
+ New window constructors.
+ New datatype constructor.
+ New C++ boolean and floating complex datatypes.

* Support for MPI-2 features not included in previous releases.

+ Generalized All-to-All collective (``Comm.Alltoallw()``)
+ User-defined data representations (``Register_datarep()``)

* New scalable implementation of reduction operations for Python
objects. This code is based on binomial tree algorithms using
point-to-point communication and duplicated communicator
contexts. To disable this feature, use
``mpi4py.rc.fast_reduce = False``.

* Backward-incompatible changes:

+ Python 2.4, 2.5, 3.0 and 3.1 are no longer supported.
+ Default MPI error handling policies are overridden. After import,
mpi4py sets the ``ERRORS_RETURN`` error handler in ``COMM_SELF``
and ``COMM_WORLD``, as well as any new ``Comm``, ``Win``, or
``File`` instance created through mpi4py, thus effectively
ignoring the MPI rules about error handler inheritance. This way,
MPI errors translate to Python exceptions. To disable this
behavior and use the standard MPI error handling rules, use
``mpi4py.rc.errors = 'default'``.
+ Change signature of all send methods,
``dest`` is a required argument.
+ Change signature of all receive and probe methods,
``source`` defaults to ``ANY_SOURCE``,
``tag`` defaults to ``ANY_TAG``.
+ Change signature of send lowercase-spelling methods,
``obj`` arguments are not mandatory.
+ Change signature of recv lowercase-spelling methods,
renamed 'obj' arguments to 'buf'.
+ Change ``Request.Waitsome()`` and ``Request.Testsome()``
to return ``None`` or ``list``.
+ Change signature of all lowercase-spelling collectives,
``sendobj`` arguments are now mandatory,
``recvobj`` arguments were removed.
+ Reduction operations ``MAXLOC`` and ``MINLOC`` are no longer
special-cased in lowercase-spelling methods ``Comm.[all]reduce()``
and ``Comm.[ex]scan()``, the input object must be specified as a
tuple ``(obj, location)``.
+ Change signature of name publishing functions.
The new signatures are
``Publish_name(service_name, port_name, info=INFO_NULL)`` and
``Unpublish_name(service_name, port_name, info=INFO_NULL).
+ ``Win`` instances now cache Python objects exposing memory by
keeping references instead of using MPI attribute caching.
+ Change signature of ``Win.Lock()``.
The new signature is
``Win.Lock(rank, lock_type=LOCK_EXCLUSIVE, assertion=0)``.
+ Move ``Cartcomm.Map()`` to ``Intracomm.Cart_map()``.
+ Move ``Graphcomm.Map()`` to ``Intracomm.Graph_map()``.
+ Remove the ``mpi4py.MPE`` module.
+ Rename the Cython definition file for use with ``cimport``
statement from ``mpi_c.pxd`` to ``libmpi.pxd``.

==========================

* Regenerate C wrappers with Cython 0.19.1 to support Python 3.3.

* Install ``*.pxd`` files in ``<site-packages>/mpi4py`` to ease the
support for Cython's ``cimport`` statement in code requiring to
access mpi4py internals.

* As a side-effect of using Cython 0.19.1, ancient Python 2.3 is no
longer supported. If you really need it, you can install an older
Cython and run ``python setup.py build_src --force``.

========================

* Now ``Comm.recv()`` accept a buffer to receive the message.

* Add ``Comm.irecv()`` and ``Request.{wait|test}[any|all]()``.

* Add ``Intracomm.Spawn_multiple()``.

* Better buffer handling for PEP 3118 and legacy buffer interfaces.

* Add support for attribute attribute caching on communicators,
datatypes and windows.

* Install MPI-enabled Python interpreter as
``<path>/mpi4py/bin/python-mpi``.

* Windows: Support for building with Open MPI.