MPICH 4.2.0 released

A new stable release of MPICH, 4.2.0, is now available for download. This is the first stable release in the 4.2.x series. It can be found on our downloads page. For the full set of commits see https://github.com/pmodels/mpich/compare/v4.1.2…v4.2.0/

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                       Changes in 4.2.0
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# Complete support MPI 4.1 specification

# Experimental thread communicator feature (e.g. MPIX_Threadcomm_init).
See paper "Frustrated With MPI+Threads? Try MPIxThreads!",
https://doi.org/10.1145/3615318.3615320.

# Experimental datatype functions MPIX_Type_iov_len and MPIX_Type_Iov

# Experimental op MPIX_EQUAL for MPI_Reduce and MPI_Allreduce (intra
communicator only)

# Use --with-{pmi,pmi2,pmix]=[path] to configure external PMI library.
Convenience options for Slurm and cray deprecated. Use
--with-pmi=oldcray for older Cray environment.

# Error checking default changed to runtime (used to be all).

# Use the error handler bound to MPI_COMM_SELF as the default error
handler.

# Use ierror instead of ierr in "use mpi" Fortran interface. This
affects user code if they call with explicit keyword, e.g. call
MPI_Init(ierr=arg). "ierror" is the correct name specified in the MPI
specification. We only added subroutine interface in "mpi.mod" since
4.1.

# Handle conversion functions, such as MPI_Comm_c2f, MPI_Comm_f2c, etc.,
are no longer macros. MPI-4.1 require these to be actual functions.

# Yaksa updated to auto detect the GPU architecture and only build for
the detected arch. This applies to CUDA and HIP support.

# MPI_Win_shared_query can be used on windows created by MPI_Win_create,
MPI_Win_allocate, in addition to windows created by
MPI_Win_allocate_shared. MPI_Win_allocate will create shared memory
whenever feasible, including between spawned processes on the same
node.

# Fortran mpi.mod support Type(c_ptr) buffer output for MPI_Alloc_mem,
MPI_Win_allocate, and MPI_Win_allocate_shared.

# New functions added in MPI-4.1: MPI_Remove_error_string,
MPI_Remove_error_code, and MPI_Remove_error_class

# New functions added in MPI-4.1: MPI_Request_get_status_all,
MPI_Request_get_status_any, and MPI_Request_get_status_some.

# New function added in MPI-4.1: MPI_Type_get_value_index.

# New functions added in MPI-4.1: MPI_Comm_attach_buffer,
MPI_Session_attach_buffer, MPI_Comm_detach_buffer,
MPI_Session_detach_buffer, MPI_Buffer_flush, MPI_Comm_flush_buffer,
MPI_Session_flush_buffer, MPI_Buffer_iflush, MPI_Comm_iflush_buffer,
and MPI_Session_iflush_buffer. Also added constant
MPI_BUFFER_AUTOMATIC to allow automatic buffers.

# Support for "mpi_memory_alloc_kinds" info key. Memory allocation kind
requests can be made via argument to mpiexec, or as info during
session creation. Kinds supported are "mpi" (with standard defined
restrictors) and "system". Queries for supported kinds can be made on
MPI objects such as sessions, comms, windows, or files. MPI 4.1 states
that supported kinds can also be found in MPI_INFO_ENV, but it was
decided at the October 2023 meeting that this was a mistake and will
be removed in an erratum.

# Fix potential crash in GPU memory hooks