CHANGES

===============================================================================
                               Changes in 5.1
===============================================================================
# MPICH is relicensed under the Apache License 2.0. Source files carry SPDX
  license identifiers.

## MPI ABI and Fortran

# Support building both MPICH-native and MPI Standard ABI libraries simultaneously
  with --enable-mpi-abi=dual. This builds both libmpi.so and libmpi_abi.so.

# Fortran 77/90/08 bindings now supported for MPI ABI builds.

# Support standalone Fortran binding that can be configured and built independently
  from the MPI C library. mpifort now explicitly links -lmpi (or -lmpi_abi).

# Split mpix.h from mpi.h. MPIX constants are available with ABI conversion support.
  libmpi_abi provides the MPIX functions (mpicc -mpi-mpix, or its alias -mpix).

# libmpi_abi no longer exports the APIs removed from the MPI standard. With
  mpicc -mpi-legacy, mpi_legacy.h maps them to their replacements; MPI_LB and
  MPI_UB are not available in the MPI ABI.

# Added pkg-config files mpich-cxx.pc and mpich-fortran.pc, the per-ABI
  files mpich-mpich-abi.pc and mpich-mpi-abi.pc (mpich.pc links to the
  default one), and the generic links mpi-c.pc, mpi-cxx.pc and mpi-fort.pc
  used by CMake's FindMPI.

# Added MPIX_Comm_create_keyval_x and related functions for Fortran-compatible keyval
  callbacks using proxy functions.

# Added MPIX_Comm_get_attr_as_fortran / MPIX_Comm_set_attr_as_fortran for proper
  Fortran attribute handling.

# Added --enable-fortran-call-pmpi configure option to control Fortran PMPI binding.

## Collectives

# Redesigned collective algorithm selection (CSEL):
  - Removed the MPID collective interfaces. The binding layer calls
    MPIR_Xxx_impl, which calls MPIR_Coll_auto for the CSEL selection.
    Device-layer algorithms (e.g. CH4 POSIX release_gather) are selected
    through the same JSON.
  - A single JSON config file, MPIR_CVAR_COLL_SELECTION_JSON_FILE, organized
    as named subtrees. MPIR_CVAR_COLL_SELECTION_TUNING_JSON_FILE is removed.
  - JSON parsing is generated from coll_algorithms.txt and uses a built-in
    parser. The json-c submodule is removed.
  - Typed algorithm parameters, a single msg_size condition (replacing
    avg_msg_size and total_msg_size), reserved restriction set names, and
    strict validation that reports unknown names as errors.
  - MPIR_CVAR_COLLECTIVE_FALLBACK=error reports an error when a forced
    algorithm cannot run.
  - The default selection is replaced with one tuned jointly on TCP and
    PSM3 networks.

# Added support for libcncoll collectives (configure --with-cnc=<prefix>),
  available as the "cnc" algorithm for 13 blocking intracommunicator
  collectives.

# Added circulant graph (circ_graph) algorithms for Bcast, Reduce, Allgather, and
  nonblocking IBcast.

# Unified design for nonblocking and persistent collectives. Compositional
  and nonblocking algorithms run their inner calls as schedules, and GPU
  buffers are swapped to host buffers within the schedule when needed.

# Added tagged nonblocking collectives for internal use. Re-implemented nonblocking
  context-id allocation (MPI_Comm_idup) using tagged collectives, removing previous
  limitations.

## CH4 and GPU

# Added GPU/NIC affinity support in OFI netmod for improved placement of GPU
  traffic across NICs. NICs are ordered once at fabric init;
  MPIR_CVAR_CH4_OFI_ENABLE_NIC_SORT=0 disables the ordering.

# Added memory registration (MR) cache for FI_HMEM_MR in OFI netmod. The
  rendezvous read/write protocols use it for device buffers.

# Delay OFI fabric initialization until first communicator creation, reducing startup
  overhead when not all contexts are used.

# Added MPL_GPU_POINTER_DEV_MMAP pointer type with cached local device buffer mmap
  for fast GPU memcpy in put/get RMA paths. The GPU IPC handle cache is
  shared across CH4 and used by OFI for small GPU staging copies.

# MPIR_CVAR_CH4_GLOBAL_PROGRESS accepts the values normal, low, and high.

## Build, documentation, and removals

# Added --disable-bash option. Compiler wrapper scripts (mpicc, mpicxx, mpifort)
  are now generated from .def templates.

# Allow external libmpl via --with-mpl-prefix.

# Converted man pages from doctext to asciidoc format. Man pages include
  semantic descriptions, and man and html pages are added for the Fortran
  conversion (f2c/c2f) functions and the Fortran-only routines.

# Removed legacy MPIO_Request API (replaced with MPI_Request).

# ROMIO: removed fallback darray/subarray support, fallback grequest support, and
  replacement Info support. Removed SGI MPI and MPIHP dependencies.

## Other

# Enum CVARs are registered with an MPI_T enum.

# CH3: added MPIR_CVAR_SOCKET_BUFFER_SIZE. MPIR_CVAR_INTERFACE_HOSTNAME is the
  primary name of the network interface CVAR.

# Software conversion of long double for the external32 data representation.

# Allow generalized request callbacks to be NULL.


===============================================================================
                               Changes in 5.0
===============================================================================
# MPI_VERSION/MPI_SUBVERSION updated to 5 and 0. MPICH now supports the MPI 5.0
  standard.

# MPIR_CHKLMEM_ and MPIR_CHKPMEM_ macros are simplified, removing non-essential
  argument such as type case and custom error messages.

# Rename MPIR_CVAR_DEBUG_PROGRESS_TIMEOUT to MPIR_CVAR_PROGRESS_TIMEOUT, and
  enable it whether or not --enable-g=progress is used in configure.

# MPICH now generates the MPI-IO bindings when ROMIO is build inside MPICH. It
  remains the same for using ROMIO outside MPICH.

# Yaksa is now maintained inside MPICH rather than as an external submodule.  

# Added internal builtin datatypes and external builtin datatypes are mapped to
  internal types. For example, both MPI_INT and MPI_INT32_T are mapped to internal
  type MPIR_INT32. NOTE: direct usage of external MPI types are disallowed
  in MPICH internally. For example, use MPIR_INT_INTERNAL to replace direct usage
  of MPI_INT. Commonly used types include MPI_BYTE, MPI_CHAR, MPI_AINT, use
  MPIR_BYTE_INTERNAL, MPIR_CHAR_INTERNAL, MPIR_AINT_INTERNAL instead. There is no
  impact to users.

# Removed MPIR_Find_{local,external}. Added in MPIR_Comm struct with attr and
  hierarchical fields to more efficiently query communicator's hierarchical
  structure.

# Use MPIR_Comm_get_{node,node_roots}_comm to obtain node_comm and node_roots_comm.
  This provides the mechanism to create subcomms on demand. In general, use
  MPIR_Subcomm_create to create subcomms. Subcomms are marked by
  MPIR_COMM_ATTR__SUBCOMM bit in the attr field. They can be much more lightweight
  than user-visible communicators.

# ADI: MPID_Comm_get_lpid removed. Lpids are looked up from the local_group and
  remote_group in the MPIR_Comm struct.

# ADI: MPID_Intercomm_exchange_map renamed to MPID_Intercomm_exchange and
  parameters now include tag, context_id, and will perform context_id exchange
  and lpid exchange.

# Added MPI_LOGICAL1, MPI_LOGICAL2, MPI_LOGICAL4, MPI_LOGICAL8, and MPI_LOGICAL16.

# Added MPIX_BFLOAT16, and added software reduction support for MPIX_BFLOAT16
  and MPIX_C_FLOAT16.

# Reworked AVX and AVX512 support. By default, MPICH will use runtime check to
  detect if AVX or AVX512 is supported. If supported, MPICH will internally use
  AVX and AVX512 for inter-NUMA and Intel GPU device memory copy operations. The
  --enable-fast=avx and --enable-fast=avx512f options now does two things: 1)
  skips the runtime check and force enables AVX and AVX512; 2) enables the usage
  of AVX and AVX512 to build the entire libmpi.so (instead of selected memory
  copy operations). A new summary in ./configure will report info on these
  usages.

# PMI 2 is now deprecated. Please consider switching to PMI 1.

# PMI 2 thread support is removed.

# PMI 1 upgraded to PMI 1.2, adding new API PMI_Barrier_group. PMI_Barrier_group
  support KVS exchange and barrier over a group of processes rather than the
  world. Usage in multiple threads is supported.

# MPI_Session_init default to MPI_THREAD_MULTIPLE. Thread levels are global. The
  first MPI_Session_init, MPI_Init, or MPI_Init_thread sets the thread level;
  the later init will ignore users request and inherit the global thread level.

# Internal collective interface replaces the last parameter "MPIR_Errflag_t errflag"
  with "int coll_attr". Use MPIR_COLL_ATTR_SYNC for internal collective usages
  where completing the synchronization is more critical than batch latency.

# CH4:OFI added native RNDV feature. Set MPIR_CVAR_CH4_OFI_EAGER_THRESHOLD to
  enable the RNDV path. The RNDV path supports the following protocols:
  pipeline, read, write, and direct.


===============================================================================
                               Changes in 4.3
===============================================================================
# Support MPI memory allocation kinds side document.

# Support MPI ABI Proposal. Configure with --enable-mpi-abi and build with
  mpicc_abi. By default, mpicc still builds and links with MPICH ABI.

# Experimental API MPIX_Op_create_x. It supports user callback function with
  extra_state context and op destructor callback. It supports language bindings
  to use proxy function for language-specific user callbacks.

# Experimental API MPIX_{Comm,File,Session,Win}_create_errhandler_x. They allow
  user error handlers to have extra_state context and corresponding destructor.
  This allows language bindings to implement user error handlers via proxy.

# Experimental API MPIX_Request_is_complete. This is a pure request state query
  function that will not invoke progress, nor will free the request. This should
  help applications that want separate task dependency checking from progress
  engine to avoid progress contentions, especially in multi-threaded context.
  It is also useful for tools to profile non-deterministic calls such as
  MPI_Test.

# Experimental API MPIX_Async_start. This function let applications to inject
  progress hooks to MPI progress. It allows application to implement custom
  asynchronous operations that will be progressed by MPI. It avoids having to
  implement separate progress mechanisms that may either take additional
  resource or contend with MPI progress and negatively impact performance. It
  also allows applications to create custom MPI operations, such as MPI
  nonblocking collectives, and achieve near native performance.

# Added benchmark tests test/mpi/bench/p2p_{latency,bw}. 

# Added CMA support in CH4 IPC.

# Added IPC read algorithm for intranode Allgather and Allgatherv.

# Added CVAR MPIR_CVAR_CH4_SHM_POSIX_TOPO_ENABLE to enable non-temporal memcpy
  for inter-numa shm communication.

# Added CVAR MPIR_CVAR_DEBUG_PROGRESS_TIMEOUT for debugging MPI deadlock issues.  

# ch4:ucx now supports dynamic processes. MPI_Comm_spawn{_multiple} will work.
  MPI_Open_port will fail due to ucx port name exceeds current MPI_MAX_PORT_NAME
  of 256. One can work around by use an info hint "port_name_size" and use a
  larger port name buffer.

# PMI-1 defines PMI_MAX_PORT_NAME, which may be different from MPI_MAX_PORT_NAME.
  This is used by "PMI_Lookup_name". Consequently, MPI_Lookup_name accepts info
  hint "port_name_size" that may be larger than MPI_MAX_PORT_NAME. If the port
  name does not fit in "port_name_size", it will return a truncation error.

# Autogen default to use -yaksa-depth=2.

# Default MPIR_CVAR_CH4_ROOTS_ONLY_PMI to on.

# Added ch4 netmod API am_tag_send and am_tag_recv.

# Added MPIR_CVAR_CH4_OFI_EAGER_THRESHOLD to force RNDV send mode.

# Make check target will run ROMIO tests.

===============================================================================
                               Changes in 4.2
===============================================================================
# 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.


===============================================================================
                               Changes in 4.1
===============================================================================

# Thread-cs in ch4 changed to per-vci.

# Testsuite (test/mpi) is configured separately from mpich configure.

# Added options in autogen to accelerate CI builds, including using pre-built
  sub-modules. Added -yaksa-depth option to generate shallower yaksa pup code
  for faster build and smaller binaries.

# Support singleton init using hydra.

# On OSX, link option flat_namespace is no longer turned on by default.

# Generate mpi.mod Fortran interfaces using Python 3. For many compilers,
  including gfortran, flags such as -fallow-mismatched-args is no longer
  necessary.

# Fixed message queue debugger interface in ch4.

# PMI (src/pmi) is refactored as a subdir and can be separately distributed.

# Added MPIX_Comm_get_failed.

# Experimental MPIX stream API to enable explicit thread contexts.

# Experimental MPIX gpu enqueue API. It currently only supports CUDA streams.

# Delays GPU resource allocation in yaksa.

# CH3 nemesis ofi netmod is removed.

# New collective algorithms. All collective algorithms are listed in
  src/mpi/coll/coll_algorithms.txt

# Removed hydra2. We will port unique features of hydra2, including
  tree-launching, to hydra in the future release.

# Added in-repository wiki documentation.

# Added stream workq to support optimizations for enqueue operations.

# Better support for large count APIs by eliminating type conversion issues.

# Hydra now uses libpmi (src/pmi) for handling PMI messages.

# Many bug fixes and enhancements.

===============================================================================
                               Changes in 4.0
===============================================================================

# All MPI-4 APIs have been implemented. Major MPI-4 features include MPI
  sessions, partitioned point-to-point communications, events in the MPI tool
  information interface, large-count functions, persistent collectives,
  MPI_Comm_idup_with_info, MPI_Isendrecv and MPI_Isendrecv_replace,
  MPI_Info_get_string, MPI_Comm_split_type with new split_type --
  MPI_COMM_TYPE_HW_GUIDED and MPI_COMM_TYPE_HW_UNGUIDED.

# Add QMPI (experimental) support.

# Add MPIX_Delete_error_{class,code,string}.

# MPI_Info objects can be accessed before MPI_Init{_thread}.

# Generate C API interface functions including man page notes and error
  checking using Python scripts.

# Generate Fortran bindings using Python scripts.

# Generate collective entrance functions and generate per-algorithm tests.

# Support explicit --without-cuda configure option.

# Drop support for UCX version < 1.7.0.

# Configure now optionally require Python 3 (when F08 is enabled).

# Multi-NIC support in ch4:ofi.

# Default to ch4:ofi when configure doesn't have a clear choice. Add message
  block at the end of configure to advise user.

# Multiple VCI is fully implemented including the active message fallback paths.

# Extend IPC to support non-contig datatypes.

# Add AMD GPU support using HIP.

# Add generic RNDV callback mechanism with active messages.

# Refactor ch4 dynamic process functions.

# Avoid building MPL and hwloc multiple times.

# Many bug fixes and code clean-ups.

===============================================================================
                               Changes in 3.4
===============================================================================

# ch4 replaces ch3 as the default device configuration. If no network
  module is specified at configuration-time, MPICH will search the
  user environment in order to select one to build. The user will be
  prompted to choose if no preferred network library is detected.

# Add support for Yaksa datatype engine (default in ch4).

# Add support for GPU buffers (CUDA, Level Zero) in pt2pt,
  collectives, and one-sided communication.

# Add support for XPMEM.

# Add support for multiple virtual communication interfaces for more
  efficient MPI_THREAD_MULTIPLE (experimental).

# Add DAOS ADIO driver to ROMIO (contributed by Intel).

# Add Quobyte ADIO driver to ROMIO (contributed by Quobyte).

# Add support for Arm compiler toolchain

# Add support for NVIDIA HPC compilers

# Add support for flang/f18 Fortran compiler

# Add support for AddressSanitizer and UndefinedBehaviorSanitizer to
  debug configuration

# Remove mxm, llc, and portals4 netmods from ch3.

# Remove support for logical reduction operations on floating point
  types.

# Remove MPIX_Mutex interfaces.

# Further improvements to ch4 business card exchange: extra
  long address support and fixes for PMIx integration.

# Un-inline non-critical ch4 code for improved build times.

# Fix several test program bugs.

# Fix several static analysis and compiler warnings.

# Change the signature of MPID_Init to include requested and provided
  thread levels.

===============================================================================
                               Changes in 3.3.2
===============================================================================

# Add support for struct sockaddr in MPICH, Hydra, and PMI socket
  code. Works with both IPv4 and IPv6 addresses.

# Fix localhost detection on FreeBSD and macOS, avoiding long delay
  during startup.

# Fix thread-local storage detection.

# Fix several test program bugs.

# Fix several static analysis and compiler warnings.

===============================================================================
                               Changes in 3.3.1
===============================================================================

 # Fix bug in MPI_Testany/MPI_Waitany that could cause deadlock

 # Add missing functionality in Argobots library support

 # Fix configure-time detection for thread local storage support

 # Better support for reproducible builds. Thanks to Bernhard
   Wiedemann for the report and fixes

 # Fix support for XL compiler toolchain

 # Add support for -static-intel linking option

 # Fix building on systems without weak symbols

 # Fix several static analysis and compiler warnings

===============================================================================
                               Changes in 3.3
===============================================================================

 # CH4 Device: A new device layer implementation designed for low software
   overheads. CH4 has experimental support for OFI and UCX network libraries,
   and POSIX shared memory. Thanks to Intel, Mellanox, and RIKEN AICS for
   participating in the CH4 coding effort.

 # Fixed SLURM integration in Hydra for new node list format.

 # Added support for PMIx (https://pmix.github.io/pmix/) client
   library in CH4 netmods. Note that you must use a compatible PMIx
   server in this configuration.

 # Better organization of collectives in the MPI layer. The new
   scheme, which de-couples implementation from selection logic,
   enables easier integration of additional algorithms.

 # TSP collectives framework: A C++-template style framework for
   collective algorithms is added to allow single collective
   implementation to move data over generic or device-specific
   transport functions.

 # Improvements to derived datatype testing (DTPools -
   https://github.com/pmodels/mpich/blob/main/doc/wiki/design/DTPools.md).

 # Added new "non-catastrophic" error codes to expose internal
   resource exhaustion.

 # Added info hints to MPI_Comm_split_type to support splitting
   communicators by machine topology. Both on-node (socket, core,
   etc.) and off-node (switch-level) hints are defined.

 # Improvements to MPI_THREAD_MULTIPLE in CH4 through new thread safety
   models at the Virtual Network Interface (VNI) level. This introduces two
   new models that leverage work-queues to offload operations and improve
   scalability under contention.

 # Message Driven Thread Activation (MDTA). An alternative locking
   model is defined for MPI_THREAD_MULTIPLE in CH4.

 # Added PMI usage optimizations for business card exchange in CH4
   netmods.

 # Improvements on MPI_Abort. MPI_Abort invoked on subcommunicators will
   only abort the connected processes within that communicator.
`
 # Cleanup of whitespace (ch3 excluded) using the
   maint/code-cleanup.sh script. For instructions on how to update
   PRs/branches based on MPICH before the cleanup, see
   https://github.com/pmodels/mpich/wiki/Code-Cleanup-Procedure.

 # Removed the PAMI device and poe PMI client.

 # C99 compiler support is now required to build MPICH.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.2..v3.3

   A list of bugs that have been fixed is available at the following
   link:

     https://github.com/pmodels/mpich/milestone/25?closed=1

===============================================================================
                               Changes in 3.2
===============================================================================

 # Added support for MPI-3.1 features including nonblocking collective I/O,
   address manipulation routines, thread-safety for MPI initialization,
   pre-init functionality, and new MPI_T routines to look up variables
   by name.

 # Fortran 2008 bindings are enabled by default and fully supported.

 # Added support for the Mellanox MXM InfiniBand interface.  (thanks
   to Mellanox for the code contribution).

 # Added support for the Mellanox HCOLL interface for collectives.
   (thanks to Mellanox for the code contribution).

 # Significant stability improvements to the MPICH/portals4
   implementation.

 # Completely revamped RMA infrastructure including several
   scalability improvements, performance improvements, and bug fixes.

 # Added experimental support for Open Fabrics Interfaces (OFI) version 1.0.0.
   https://github.com/ofiwg/libfabric (thanks to Intel for code contribution)

 # The Myrinet MX network module, which had a life cycle from 1.1 till
   3.1.2, has now been deleted.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.1.3..v3.2

   A full list of bugs that have been fixed is available at the
   following link:

     https://trac.mpich.org/projects/mpich/query?status=closed&group=resolution&milestone=mpich-3.2


===============================================================================
                               Changes in 3.1.3
===============================================================================

 # Several enhancements to Portals4 support.

 # Several enhancements to PAMI (thanks to IBM for the code contribution).

 # Several enhancements to the CH3 RMA implementation.

 # Several enhancements to ROMIO.

 # Fixed deadlock in multi-threaded MPI_Comm_idup.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.1.2..v3.1.3

   A full list of bugs that have been fixed is available at the
   following link:

     https://trac.mpich.org/projects/mpich/query?status=closed&group=resolution&milestone=mpich-3.1.3


===============================================================================
                               Changes in 3.1.2
===============================================================================

 # Significant enhancements to the BG/Q device, especially for RMA and
   shared memory functionality.

 # Several enhancements to ROMIO.

 # Upgraded to hwloc-1.9.

 # Added more Fortran 2008 (F08) tests and fixed a few F08 binding bugs.
   Now all MPICH F90 tests have been ported to F08.

 # Updated weak alias support to align with gcc-4.x

 # Minor enhancements to the CH3 RMA implementation.

 # Better implementation of MPI_Allreduce for intercommunicator.

 # Added environment variables to control memory tracing overhead.

 # Added flags to enable C99 mode with Solaris compilers.

 # Updated implementation of MPI-T CVARs of type MPI_CHAR, as interpreted
   in MPI-3.0 Errata.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.1.1..v3.1.2

   A full list of bugs that have been fixed is available at the
   following link:

     https://trac.mpich.org/projects/mpich/query?status=closed&group=resolution&milestone=mpich-3.1.2


===============================================================================
                               Changes in 3.1.1
===============================================================================

 # Blue Gene/Q implementation supports MPI-3. This release contains a
   functional and compliant Blue Gene/Q implementation of the MPI-3 standard.
   Instructions to build on Blue Gene/Q are on the mpich.org wiki:
   https://github.com/pmodels/mpich/blob/main/doc/wiki/source_code/BGQ.md

 # Fortran 2008 bindings (experimental). Build with --enable-fortran=all. Must have
   a Fortran 2008 + TS 29113 capable compiler.

 # Significant rework of MPICH library management and which symbols go
   into which libraries.  Also updated MPICH library names to make
   them consistent with Intel MPI, Cray MPI and IBM PE MPI.  Backward
   compatibility links are provided for older mpich-based build
   systems.

 # The ROMIO "Blue Gene" driver has seen significant rework.  We have separated
   "file system" features from "platform" features, since GPFS shows up in more
   places than just Blue Gene

 # New ROMIO options for aggregator selection and placement on Blue Gene

 # Optional new ROMIO two-phase algorithm requiring less communication for
   certain workloads

 # The old ROMIO optimization "deferred open" either stopped working or was
   disabled on several platforms.

 # Added support for powerpcle compiler. Patched libtool in MPICH to support
   little-endian powerpc linux host.

 # Fixed the prototype of the Reduce_local C++ binding.  The previous
   prototype was completely incorrect.  Thanks to Jeff Squyres for
   reporting the issue.

 # The mpd process manager, which was deprecated and unsupported for
   the past four major release series (1.3.x till 3.1), has now been
   deleted.  RIP.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.1..v3.1.1

   A full list of bugs that have been fixed is available at the
   following link:

     https://trac.mpich.org/projects/mpich/query?status=closed&group=resolution&milestone=mpich-3.1.1


===============================================================================
                               Changes in 3.1
===============================================================================

 # Implement runtime compatibility with MPICH-derived implementations as per
   the ABI Compatibility Initiative (see www.mpich.org/abi for more
   information).

 # Integrated MPICH-PAMI code base for Blue Gene/Q and other IBM
   platforms.

 # Several improvements to the SCIF netmod.  (code contribution from
   Intel).

 # Major revamp of the MPI_T interface added in MPI-3.

 # Added environment variables to control a lot more capabilities for
   collectives.  See the README.envvar file for more information.

 # Allow non-blocking collectives and fault tolerance at the same
   time. The option MPIR_PARAM_ENABLE_COLL_FT_RET has been deprecated as
   it is no longer necessary.

 # Improvements to MPI_WIN_ALLOCATE to internally allocate shared
   memory between processes on the same node.

 # Performance improvements for MPI RMA operations on shared memory
   for MPI_WIN_ALLOCATE and MPI_WIN_ALLOCATE_SHARED.

 # Enable shared library builds by default.

 # Upgraded hwloc to 1.8.

 # Several improvements to the Hydra-SLURM integration.

 # Several improvements to the Hydra process binding code.  See the
   Hydra wiki page for more information:
   https://github.com/pmodels/mpich/blob/main/doc/wiki/how_to/Using_the_Hydra_Process_Manager.md

 # MPICH now supports operations on very large datatypes (those that describe
   more than 32 bits of data).  This work also allows MPICH to fully support
   MPI-3's introduction of MPI_Count.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.

   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.0.4..v3.1

   A full list of bugs that have been fixed is available at the
   following link:

     https://trac.mpich.org/projects/mpich/query?status=closed&group=resolution&milestone=mpich-3.1


===============================================================================
                               Changes in 3.0.4
===============================================================================

 # BUILD SYSTEM: Reordered the default compiler search to prefer Intel
   and PG compilers over GNU compilers because of the performance
   difference.

   WARNING: If you do not explicitly specify the compiler you want
   through CC and friends, this might break ABI for you relative to
   the previous 3.0.x release.

 # OVERALL: Added support to manage per-communicator eager-rendezvous
   thresholds.

 # PM/PMI: Performance improvements to the Hydra process manager on
   large-scale systems by allowing for key/value caching.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.0.3..v3.0.4


===============================================================================
                               Changes in 3.0.3
===============================================================================

 # RMA: Added a new mechanism for piggybacking RMA synchronization operations,
   which improves the performance of several synchronization operations,
   including Flush.

 # RMA: Added an optimization to utilize the MPI_MODE_NOCHECK assertion in
   passive target RMA to improve performance by eliminating a lock request
   message.

 # RMA: Added a default implementation of shared memory windows to CH3.  This
   adds support for this MPI 3.0 feature to the ch3:sock device.

 # RMA: Fix a bug that resulted in an error when RMA operation request handles
   where completed outside of a synchronization epoch.

 # PM/PMI: Upgraded to hwloc-1.6.2rc1.  This version uses libpciaccess
   instead of libpci, to workaround the GPL license used by libpci.

 # PM/PMI: Added support for the Cobalt process manager.

 # BUILD SYSTEM: allow MPI_LONG_DOUBLE_SUPPORT to be disabled with a configure
   option.

 # FORTRAN: fix MPI_WEIGHTS_EMPTY in the Fortran bindings

 # MISC: fix a bug in MPI_Get_elements where it could return incorrect values

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.0.2..v3.0.3


===============================================================================
                               Changes in 3.0.2
===============================================================================

 # PM/PMI: Upgrade to hwloc-1.6.1

 # RMA: Performance enhancements for shared memory windows.

 # COMPILER INTEGRATION: minor improvements and fixes to the clang static type
   checking annotation macros.

 # MPI-IO (ROMIO): improved error checking for user errors, contributed by IBM.

 # MPI-3 TOOLS INTERFACE: new MPI_T performance variables providing information
   about nemesis communication behavior and and CH3 message matching queues.

 # TEST SUITE: "make testing" now also outputs a "summary.tap" file that can be
   interpreted with standard TAP consumer libraries and tools.  The
   "summary.xml" format remains unchanged.

 # GIT: This is the first release built from the new git repository at
   git.mpich.org.  A few build system mechanisms have changed because of this
   switch.

 # BUG FIX: resolved a compilation error related to LLONG_MAX that affected
   several users (ticket #1776).

 # BUG FIX: nonblocking collectives now properly make progress when MPICH is
   configured with the ch3:sock channel (ticket #1785).

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available at the following link:

     http://git.mpich.org/mpich.git/shortlog/v3.0.1..v3.0.2


===============================================================================
                               Changes in 3.0.1
===============================================================================

 # PM/PMI: Critical bug-fix in Hydra to work correctly in multi-node
   tests.

 # A full list of changes is available using:

     svn log -r10790:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich-3.0.1

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich-3.0.1?action=follow_copy&rev=HEAD&stop_rev=10790&mode=follow_copy


===============================================================================
                               Changes in 3.0
===============================================================================

 # MPI-3: All MPI-3 features are now implemented and the MPI_VERSION
   bumped up to 3.0.

 # OVERALL: Added support for ARM-v7 native atomics

 # MPE: MPE is now separated out of MPICH and can be downloaded/used
   as a separate package.

 # PM/PMI: Upgraded to hwloc-1.6

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r10344:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich-3.0

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich-3.0?action=follow_copy&rev=HEAD&stop_rev=10344&mode=follow_copy


===============================================================================
                               Changes in 1.5
===============================================================================

 # OVERALL: Nemesis now supports an "--enable-yield=..." configure
   option for better performance/behavior when oversubscribing
   processes to cores.  Some form of this option is enabled by default
   on Linux, Darwin, and systems that support sched_yield().

 # OVERALL: Added support for Intel Many Integrated Core (MIC)
   architecture: shared memory, TCP/IP, and SCIF based communication.

 # OVERALL: Added support for IBM BG/Q architecture.  Thanks to IBM
   for the contribution.

 # MPI-3: const support has been added to mpi.h, although it is
   disabled by default.  It can be enabled on a per-translation unit
   basis with "#define MPICH2_CONST const".

 # MPI-3: Added support for MPIX_Type_create_hindexed_block.

 # MPI-3: The new MPI-3 nonblocking collective functions are now
   available as "MPIX_" functions (e.g., "MPIX_Ibcast").

 # MPI-3: The new MPI-3 neighborhood collective routines are now available as
   "MPIX_" functions (e.g., "MPIX_Neighbor_allgather").

 # MPI-3: The new MPI-3 MPI_Comm_split_type function is now available
   as an "MPIX_" function.

 # MPI-3: The new MPI-3 tools interface is now available as "MPIX_T_"
   functions.  This is a beta implementation right now with several
   limitations, including no support for multithreading.  Several
   performance variables related to CH3's message matching are exposed
   through this interface.

 # MPI-3: The new MPI-3 matched probe functionality is supported via
   the new routines MPIX_Mprobe, MPIX_Improbe, MPIX_Mrecv, and
   MPIX_Imrecv.

 # MPI-3: The new MPI-3 nonblocking communicator duplication routine,
   MPIX_Comm_idup, is now supported.  It will only work for
   single-threaded programs at this time.

 # MPI-3: MPIX_Comm_reenable_anysource support

 # MPI-3: Native MPIX_Comm_create_group support (updated version of
   the prior MPIX_Group_comm_create routine).

 # MPI-3: MPI_Intercomm_create's internal communication no longer interferes
   with point-to-point communication, even if point-to-point operations on the
   parent communicator use the same tag or MPI_ANY_TAG.

 # MPI-3: Eliminated the possibility of interference between
   MPI_Intercomm_create and point-to-point messaging operations.

 # Build system: Completely revamped build system to rely fully on
   autotools.  Parallel builds ("make -j8" and similar) are now supported.

 # Build system: rename "./maint/updatefiles" --> "./autogen.sh" and
   "configure.in" --> "configure.ac"

 # JUMPSHOT: Improvements to Jumpshot to handle thousands of
   timelines, including performance improvements to slog2 in such
   cases.

 # JUMPSHOT: Added navigation support to locate chosen drawable's ends
   when viewport has been scrolled far from the drawable.

 # PM/PMI: Added support for memory binding policies.

 # PM/PMI: Various improvements to the process binding support in
   Hydra.  Several new pre-defined binding options are provided.

 # PM/PMI: Upgraded to hwloc-1.5

 # PM/PMI: Several improvements to PBS support to natively use the PBS
   launcher.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r8478:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.5

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.5?action=follow_copy&rev=HEAD&stop_rev=8478&mode=follow_copy


===============================================================================
                               Changes in 1.4.1
===============================================================================

 # OVERALL: Several improvements to the ARMCI API implementation
   within MPICH2.

 # Build system: Added beta support for DESTDIR while installing
   MPICH2.

 # PM/PMI: Upgrade hwloc to 1.2.1rc2.

 # PM/PMI: Initial support for the PBS launcher.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r8675:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.4.1

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.4.1?action=follow_copy&rev=HEAD&stop_rev=8675&mode=follow_copy


===============================================================================
                               Changes in 1.4
===============================================================================

 # OVERALL: Improvements to fault tolerance for collective
   operations. Thanks to Rui Wang @ ICT for reporting several of these
   issues.

 # OVERALL: Improvements to the universe size detection. Thanks to
   Yauheni Zelenko for reporting this issue.

 # OVERALL: Bug fixes for Fortran attributes on some systems. Thanks
   to Nicolai Stange for reporting this issue.

 # OVERALL: Added new ARMCI API implementation (experimental).

 # OVERALL: Added new MPIX_Group_comm_create function to allow
   non-collective creation of sub-communicators.

 # FORTRAN: Bug fixes in the MPI_DIST_GRAPH_ Fortran bindings.

 # PM/PMI: Support for a manual "none" launcher in Hydra to allow for
   higher-level tools to be built on top of Hydra. Thanks to Justin
   Wozniak for reporting this issue, for providing several patches for
   the fix, and testing it.

 # PM/PMI: Bug fixes in Hydra to handle non-uniform layouts of hosts
   better. Thanks to the MVAPICH group at OSU for reporting this issue
   and testing it.

 # PM/PMI: Bug fixes in Hydra to handle cases where only a subset of
   the available launchers or resource managers are compiled
   in. Thanks to Satish Balay @ Argonne for reporting this issue.

 # PM/PMI: Support for a different username to be provided for each
   host; this only works for launchers that support this (such as
   SSH).

 # PM/PMI: Bug fixes for using Hydra on AIX machines. Thanks to
   Kitrick Sheets @ NCSA for reporting this issue and providing the
   first draft of the patch.

 # PM/PMI: Bug fixes in memory allocation/management for environment
   variables that was showing up on older platforms. Thanks to Steven
   Sutphen for reporting the issue and providing detailed analysis to
   track down the bug.

 # PM/PMI: Added support for providing a configuration file to pick
   the default options for Hydra. Thanks to Saurabh T. for reporting
   the issues with the current implementation and working with us to
   improve this option.

 # PM/PMI: Improvements to the error code returned by Hydra.

 # PM/PMI: Bug fixes for handling "=" in environment variable values in
   hydra.

 # PM/PMI: Upgrade the hwloc version to 1.2.

 # COLLECTIVES: Performance and memory usage improvements for MPI_Bcast
   in certain cases.

 # VALGRIND: Fix incorrect Valgrind client request usage when MPICH2 is
   built for memory debugging.

 # BUILD SYSTEM: "--enable-fast" and "--disable-error-checking" are once
   again valid simultaneous options to configure.

 # TEST SUITE: Several new tests for MPI RMA operations.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r7838:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.4

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.4?action=follow_copy&rev=HEAD&stop_rev=7838&mode=follow_copy


===============================================================================
                               Changes in 1.3.2
===============================================================================

 # OVERALL: MPICH2 now recognizes the OSX mach_absolute_time as a
   native timer type.

 # OVERALL: Performance improvements to MPI_Comm_split on large
   systems.

 # OVERALL: Several improvements to error returns capabilities in the
   presence of faults.

 # PM/PMI: Several fixes and improvements to Hydra's process binding
   capability.

 # PM/PMI: Upgrade the hwloc version to 1.1.1.

 # PM/PMI: Allow users to sort node lists allocated by resource
   managers in Hydra.

 # PM/PMI: Improvements to signal handling. Now Hydra respects Ctrl-Z
   signals and passes on the signal to the application.

 # PM/PMI: Improvements to STDOUT/STDERR handling including improved
   support for rank prepending on output. Improvements to STDIN
   handling for applications being run in the background.

 # PM/PMI: Split the bootstrap servers into "launchers" and "resource
   managers", allowing the user to pick a different resource manager
   from the launcher. For example, the user can now pick the "SLURM"
   resource manager and "SSH" as the launcher.

 # PM/PMI: The MPD process manager is deprecated.

 # PM/PMI: The PLPA process binding library support is deprecated.

 # WINDOWS: Adding support for gfortran and 64-bit gcc libs.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r7457:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.3.2

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.3.2?action=follow_copy&rev=HEAD&stop_rev=7457&mode=follow_copy


===============================================================================
                               Changes in 1.3.1
===============================================================================

 # OVERALL: MPICH2 is now fully compliant with the CIFTS FTB standard
   MPI events (based on the draft standard).

 # OVERALL: Major improvements to RMA performance for long lists of
   RMA operations.

 # OVERALL: Performance improvements for Group_translate_ranks.

 # COLLECTIVES: Collective algorithm selection thresholds can now be controlled
   at runtime via environment variables.

 # ROMIO: PVFS error codes are now mapped to MPI error codes.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r7350:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.3.1

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.3.1?action=follow_copy&rev=HEAD&stop_rev=7350&mode=follow_copy


===============================================================================
                               Changes in 1.3
===============================================================================

 # OVERALL: Initial support for fine-grained threading in
   ch3:nemesis:tcp.

 # OVERALL: Support for Asynchronous Communication Progress.

 # OVERALL: The ssm and shm channels have been removed.

 # OVERALL: Checkpoint/restart support using BLCR.

 # OVERALL: Improved tolerance to process and communication failures
   when error handler is set to MPI_ERRORS_RETURN.  If a communication
   operation fails (e.g., due to a process failure) MPICH2 will return
   an error, and further communication to that process is not
   possible.  However, communication with other processes will still
   proceed normally.  Note, however, that the behavior collective
   operations on communicators containing the failed process is
   undefined, and may give incorrect results or hang some processes.

 # OVERALL: Experimental support for inter-library dependencies.

 # PM/PMI: Hydra is now the default process management framework
   replacing MPD.

 # PM/PMI: Added dynamic process support for Hydra.

 # PM/PMI: Added support for LSF, SGE and POE in Hydra.

 # PM/PMI: Added support for CPU and memory/cache topology aware
   process-core binding.

 # DEBUGGER: Improved support and bug fixes in the Totalview support.

 # Build system: Replaced F90/F90FLAGS by FC/FCFLAGS. F90/F90FLAGS are
   not longer supported in the configure.

 # Multi-compiler support: On systems where C compiler that is used to
   build mpich2 libraries supports multiple weak symbols and multiple aliases,
   the Fortran binding built in the mpich2 libraries can handle different
   Fortran compilers (than the one used to build mpich2).  Details in README.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r5762:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.3

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.3?action=follow_copy&rev=HEAD&stop_rev=5762&mode=follow_copy


===============================================================================
                               Changes in 1.2.1
===============================================================================

 # OVERALL: Improved support for fine-grained multithreading.

 # OVERALL: Improved integration with Valgrind for debugging builds of MPICH2.

 # PM/PMI: Initial support for hwloc process-core binding library in
   Hydra.

 # PM/PMI: Updates to the PMI-2 code to match the PMI-2 API and
   wire-protocol draft.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r5425:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.2.1

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.2.1?action=follow_copy&rev=HEAD&stop_rev=5425&mode=follow_copy


===============================================================================
                               Changes in 1.2
===============================================================================

 # OVERALL: Support for MPI-2.2

 # OVERALL: Several fixes to Nemesis/MX.

 # WINDOWS: Performance improvements to Nemesis/windows.

 # PM/PMI: Scalability and performance improvements to Hydra using
   PMI-1.1 process-mapping features.

 # PM/PMI: Support for process-binding for hyperthreading enabled
   systems in Hydra.

 # PM/PMI: Initial support for PBS as a resource management kernel in
   Hydra.

 # PM/PMI: PMI2 client code is now officially included in the release.

 # TEST SUITE: Support to run the MPICH2 test suite through valgrind.

 # Several other minor bug fixes, memory leak fixes, and code cleanup.
   A full list of changes is available using:

     svn log -r5025:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.2

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.2?action=follow_copy&rev=HEAD&stop_rev=5025&mode=follow_copy


===============================================================================
                               Changes in 1.1.1p1
===============================================================================

 - OVERALL: Fixed an invalid read in the dataloop code for zero count types.

 - OVERALL: Fixed several bugs in ch3:nemesis:mx (tickets #744,#760;
   also change r5126).

 - BUILD SYSTEM: Several fixes for functionality broken in 1.1.1 release,
   including MPICH2LIB_xFLAGS and extra libraries living in $LIBS instead of
   $LDFLAGS.  Also, '-lpthread' should no longer be duplicated in link lines.

 - BUILD SYSTEM: MPICH2 shared libraries are now compatible with glibc versioned
   symbols on Linux, such as those present in the MX shared libraries.

 - BUILD SYSTEM: Minor tweaks to improve compilation under the nvcc CUDA
   compiler.

 - PM/PMI: Fix mpd incompatibility with python2.3 introduced in mpich2-1.1.1.

 - PM/PMI: Several fixes to hydra, including memory leak fixes and process
   binding issues.

 - TEST SUITE: Correct invalid arguments in the coll2 and coll3 tests.

 - Several other minor bug fixes, memory leak fixes, and code cleanup.  A full
   list of changes is available using:

     svn log -r5032:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.1.1p1

     ... or at the following link:

     https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.1.1p1?action=follow_copy&rev=HEAD&stop_rev=5032&mode=follow_copy


===============================================================================
                               Changes in 1.1.1
===============================================================================

 # OVERALL: Improved support for Boost MPI.

 # PM/PMI: Significantly improved time taken by MPI_Init with Nemesis and MPD on
   large numbers of processes.

 # PM/PMI: Improved support for hybrid MPI-UPC program launching with
   Hydra.

 # PM/PMI: Improved support for process-core binding with Hydra.

 # PM/PMI: Preliminary support for PMI-2. Currently supported only
   with Hydra.

 # Many other bug fixes, memory leak fixes and code cleanup. A full
   list of changes is available using:

  svn log -r4655:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.1.1

  ... or at the following link:

  https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.1.1?action=follow_copy&rev=HEAD&stop_rev=4655&mode=follow_copy


===============================================================================
                               Changes in 1.1
===============================================================================

- OVERALL: Added MPI 2.1 support.

- OVERALL: Nemesis is now the default configuration channel with a
  completely new TCP communication module.

- OVERALL: Windows support for nemesis.

- OVERALL: Added a new Myrinet MX network module for nemesis.

- OVERALL: Initial support for shared-memory aware collective
  communication operations.  Currently MPI_Bcast, MPI_Reduce, MPI_Allreduce,
  and MPI_Scan.

- OVERALL: Improved handling of MPI Attributes.

- OVERALL: Support for BlueGene/P through the DCMF library (thanks to
  IBM for the patch).

- OVERALL: Experimental support for fine-grained multithreading

- OVERALL: Added dynamic processes support for Nemesis.

- OVERALL: Added automatic as well as statically runtime configurable
  receive timeout variation for MPD (thanks to OSU for the patch).

- OVERALL: Improved performance for MPI_Allgatherv, MPI_Gatherv, and MPI_Alltoall.

- PM/PMI: Initial support for the new Hydra process management
  framework (current support is for ssh, rsh, fork and a preliminary
  version of slurm).

- ROMIO: Added support for MPI_Type_create_resized and
  MPI_Type_create_indexed_block datatypes in ROMIO.

- ROMIO: Optimized Lustre ADIO driver (thanks to Weikuan Yu for
  initial work and Sun for further improvements).

- Many other bug fixes, memory leak fixes and code cleanup. A full
  list of changes is available using:

  svn log -r813:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/tags/release/mpich2-1.1

  ... or at the following link:

  https://trac.mcs.anl.gov/projects/mpich2/log/mpich2/tags/release/mpich2-1.1?action=follow_copy&rev=HEAD&stop_rev=813&mode=follow_copy


===============================================================================
                               Changes in 1.0.7
===============================================================================

- OVERALL: Initial ROMIO device for BlueGene/P (the ADI device is also
added but is not configurable at this time).

- OVERALL: Major clean up for the propagation of user-defined and
other MPICH2 flags throughout the code.

- OVERALL: Support for STI Cell Broadband Engine.

- OVERALL: Added datatype free hooks to be used by devices
independently.

- OVERALL: Added device-specific timer support.

- OVERALL: make uninstall works cleanly now.

- ROMIO: Support to take hints from a config file

- ROMIO: more tests and bug fixes for nonblocking I/O

- PM/PMI: Added support to use PMI Clique functionality for process
managers that support it.

- PM/PMI: Added SLURM support to configure to make it transparent to
users.

- PM/PMI: SMPD Singleton Init support.

- WINDOWS: Fortran 90 support added.

- SCTP: Added MPICH_SCTP_NAGLE_ON support.

- MPE: Updated MPE logging API so that it is thread-safe (through
global mutex).

- MPE: Added infrastructure to piggyback argument data to MPI states.

- DOCS: Documentation creation now works correctly for VPATH builds.

- Many other bug fixes, memory leak fixes and code cleanup. A full
list of changes is available using:
  svn log -r100:HEAD https://svn.mcs.anl.gov/repos/mpi/mpich2/branches/release/MPICH2_1_0_7


===============================================================================
			       Changes in 1.0.6
===============================================================================

- Updates to the ch3:nemesis channel including preliminary support for
thread safety.

- Preliminary support for dynamic loading of ch3 channels (sock, ssm,
shm). See the README file for details.

- Singleton init now works with the MPD process manager.

- Fixes in MPD related to MPI-2 connect-accept.

- Improved support for MPI-2 generalized requests that allows true
nonblocking I/O in ROMIO.

- MPE changes:
  * Enabled thread-safe MPI logging through global mutex.
  * Enhanced Jumpshot to be more thread friendly
    + added simple statistics in the Legend windows.
  * Added backtrace support to MPE on Solaris and glibc based systems,
    e.g. Linux.  This improves the output error message from the 
    Collective/Datatype checking library.
  * Fixed the CLOG2 format so it can be used in serial (non-MPI) logging.

- Performance improvements for derived datatypes (including packing
and communication) through in-built loop-unrolling and buffer
alignment.

- Performance improvements for MPI_Gather when non-power-of-two
processes are used, and when a non-zero ranked root is performing the
gather.

- MPI_Comm_create works for intercommunicators.

- Enabled -O2 and equivalent compiler optimizations for supported
compilers by default (including GNU, Intel, Portland, Sun, Absoft,
IBM).

- Many other bug fixes, memory leak fixes and code cleanup. A full
list of changes is available at
www.mcs.anl.gov/mpi/mpich2/mpich2_1_0_6changes.htm.


===============================================================================
			       Changes in 1.0.5
===============================================================================

- An SCTP channel has been added to the CH3 device. This was
  implemented by Brad Penoff and Mike Tsai, Univ. of British Columbia.
  Their group's webpage is located at http://www.cs.ubc.ca/labs/dsg/mpi-sctp/ .

- Bugs related to dynamic processes have been fixed.

- Performance-related fixes have been added to derived datatypes and
  collective communication.

- Updates to the Nemesis channel

- Fixes to thread safety for the ch3:sock channel

- Many other bug fixes and code cleanup.  A full list of changes is available 
  at www.mcs.anl.gov/mpi/mpich2/mpich2_1_0_5changes.htm . 


===============================================================================
			       Changes in 1.0.4
===============================================================================

- For the ch3:sock channel, the default build of MPICH2 supports
  thread safety. A separate build is not needed as before. However, 
  thread safety is enabled only if the user calls MPI_Init_thread with  
  MPI_THREAD_MULTIPLE. If not, no thread locks are called, so there
  is no penalty.

- A new low-latency channel called Nemesis has been added. It can be
  selected by specifying the option --with-device=ch3:nemesis.
  Nemesis uses shared memory for intranode communication and various
  networks for internode communication.  Currently available networks
  are TCP, GM and MX.  Nemesis is still a work in progress.  See the
  README for more information about the channel.

- Support has been added for providing message queues to debuggers.
  Configure with --enable-debuginfo to make this information available.
  This is still a "beta" test version and has not been extensively tested.

- For systems with firewalls, the environment variable MPICH_PORT_RANGE can
  be used to restrict the range of ports used by MPICH2.  See the documentation
  for more details.

- Withdrew obsolete modules, including the ib and rdma communication layers.
  For Infiniband and MPICH2, please see 
  http://nowlab.cse.ohio-state.edu/projects/mpi-iba/ 
  For other interconnects, please contact us at mpich2-maint@mcs.anl.gov .

- Numerous bug fixes and code cleanup.  A full list of changes is available 
  at www.mcs.anl.gov/mpi/mpich2/mpich2_1_0_4changes.htm . 

- Numerous new tests in the MPICH2 test suite.

- For developers, the way in which information is passed between the top
  level configure and configures in the device, process management, and
  related modules has been cleaned up.  See the comments at the beginning
  of the top-level configure.in for details.  This change makes it easier
  to interface other modules to MPICH2.


===============================================================================
			       Changes in 1.0.3
===============================================================================

- There are major changes to the ch3 device implementation.  Old and 
  unsupported channels (essm, rdma) have been removed.   The
  internal interface between ch3 and the channels has been improved to 
  similify the process of adding a new channel (sharing existing code
  where possible) and to improve performance.  Further changes in this
  internal interface are expected.

- Numerous bug fixes and code cleanup

        Creation of intercommunicators and intracommunicators 
        from the intercommunicators created with Spawn and Connect/Accept

        The computation of the alignment and padding of items within
        structures now handles additional cases, including systems 
        where the alignment an padding depends on the type of the first
	item in the structure

        MPD recognizes wdir info keyword

        gforker's mpiexec supports -env and -genv arguments for controlling
        which environment variables are delivered to created processes

- While not a bug, to aid in the use of memory trace packages, MPICH2
  tries to free all allocated data no later than when MPI_Finalize
  returns.

- Support for DESTDIR in install targets

- Enhancements to SMPD

- In order to support special compiler flags for users that may be
  different from those used to build MPICH2, the environment variables
  MPI_CFLAGS, MPI_FFLAGS, MPI_CXXFLAGS, and MPI_F90FLAGS may be used
  to specify the flags used in mpicc, mpif77, mpicxx, and mpif90 
  respectively.  The flags CFLAGS, FFLAGS, CXXFLAGS, and F90FLAGS are
  used in the building of MPICH2.

- Many enhancements to MPE

- Enhanced support for features and idiosyncrasies of Fortran 77 and 
  Fortran 90 compilers, including gfortran, g95, and xlf

- Enhanced support for C++ compilers that do not fully support abstract
  base classes

- Additional tests in the mpich2/tests/mpi
    
- New FAQ included (also available at
    http://www.mcs.anl.gov/mpi/mpich2/faq.htm) 

- Man pages for mpiexec and mpif90

- Enhancements for developers, including a more flexible and general 
  mechanism for inserting logging and information messages, controllable
  with --mpich-dbg-xxx command line arguments or MPICH_DBG_XXX environment
  variables.

- Note to developers: 
  This release contains many changes to the structure of the CH3
  device implementation (in src/mpid/ch3), including significant
  reworking of the files (many files have been combined into fewer files
  representing logical grouping of functions).  The next release of 
  MPICH2 will contain even more significant changes to the device 
  structure as we introduce a new communication implementation.
 
===============================================================================
			       Changes in 1.0.2
===============================================================================

- Optimizations to the MPI-2 one-sided communication functions for the
  sshm (scalable shared memory) channel when window memory is
  allocated with MPI_Alloc_mem (for all three synchronization methods).

- Numerous bug fixes and code cleanup. 

- Fixed memory leaks.

- Fixed shared library builds.

- Fixed performance problems with MPI_Type_create_subarray/darray 

- The following changes have been made to MPE2:

  - MPE2 now builds the MPI collective and datatype checking library
    by default. 

  - SLOG-2 format has been upgraded to 2.0.6 which supports event drawables
    and provides count of real drawables in preview drawables.

  - new slog2 tools, slog2filter and slog2updater, which both are logfile
    format converters.  slog2filter removes undesirable categories of
    drawables as well as alters the slog2 file structure.  slog2updater
    is a slog2filter that reads in older logfile format, 2.0.5, and 
    writes out the latest format 2.0.6.

- The following changes have been made to MPD:

  - Nearly all code has been replaced by new code that follows a more
    object-oriented approach than before.  This has not changed any
    fundamental behavior or interfaces.

  - There is info support in spawn and spawn_multiple for providing
    parts of the environment for spawned processes such as search-path
    and current working directory.  See the Standard for the required
    fields.

  - mpdcheck has been enhanced to help users debug their cluster and
    network configurations.

  - CPickle has replaced marshal as the source module for dumps and loads.

  - The mpigdb command has been replaced by mpiexec -gdb.

  - Alternate interfaces can be used.  See the Installer's Guide.
 

===============================================================================
			       Changes in 1.0.1
===============================================================================

- Copyright statements have been added to all code files, clearly identifying
  that all code in the distribution is covered by the extremely flexible
  copyright described in the COPYRIGHT file.

- The MPICH2 test suite (mpich2/test) can now be run against any MPI
  implementation, not just MPICH2.

- The send and receive socket buffers sizes may now be changed by setting
  MPICH_SOCKET_BUFFER_SIZE.  Note: the operating system may impose a maximum
  socket buffer size that prohibits MPICH2 from increasing the buffers to the
  desire size.  To raise the maximum allowable buffer size, please contact your
  system administrator.

- Error handling throughout the MPI routines has been improved.  The error
  handling in some internal routines has been simplified as well, making the
  routines easier to read.

- MPE (Jumpshot and CLOG logging) is now supported on Microsoft Windows.

- C applications built for Microsoft Windows may select the desired channels at
  runtime.

- A program not started with mpiexec may become an MPI program by calling
  MPI_Init.  It will have an MPI_COMM_WORLD of size one.  It may then call
  other MPI routines, including MPI_COMM_SPAWN, to become a truly parallel
  program.  At present, the use of MPI_COMM_SPAWN and MPI_COMM_SPAWN_MULTIPLE
  by such a process is only supported by the MPD process manager.

- Memory leaks in communicator allocation and the C++ binding have been fixed.

- Following GNU guidelines, the parts of the install step that checked the
  installation have been moved to an installcheck target.  Much of the
  installation now supports the DESTDIR prefix.

- Microsoft Visual Studio projects have been added to make it possible to build
  x86-64 version

- Problems with compilers and linkers that do not support weak symbols, which
  are used to support the PMPI profiling interface, have been corrected.

- Handling of Fortran 77 and Fortran 90 compilers has been improved, including
  support for g95.

- The Fortran stdcall interface on Microsoft Windows now supports character*.

- A bug in the OS X implementation of poll() caused the sock channel to hang.
  A workaround has been put in place.

- Problems with installation under OS/X are now detected and corrected.
  (Install breaks libraries that are more than 10 seconds old!)

- The following changes have been made to MPD:

  - Sending a SIGINT to mpiexec/mpdrun, such as by typing control-C, now causes
    SIGINT to be sent to the processes within the job.  Previously, SIGKILL was
    sent to the processes, preventing applications from catching the signal 
    and performing their own signal processing.

  - The process for merging output has been improved.

  - A new option, -ifhn, has been added to the machine file, allowing the user
    to select the destination interface to be used for TCP communication.  See
    the User's Manual for details.

  - The user may now select, via the "-s" option to mpiexec/mpdrun, which
    processes receive input through stdin.  stdin is immediately closed for all
    processes not in set receiving input.  This prevents processes not in the
    set from hanging should they attempt to read from stdin.

  - The MPICH2 Installer's Guide now contains an appendix on troubleshooting
    problems with MPD.

- The following changes have been made to SMPD:

  - On Windows machines, passwordless authentication (via SSPI) can now be used
    to start processes on machines within a domain.  This feature is a recent
    addition, and should be considered experimental.

  - On Windows machines, the -localroot option was added to mpiexec, allowing
    processes on the local machines to perform GUI operations on the local
    desktop.

  - On Windows machines, network drive mapping is now supported via the -map
    option to mpiexec.

  - Three new GUI tools have been added for Microsoft Windows.  These tools are
    wrappers to the command line tools, mpiexec.exe and smpd.exe.  wmpiexec
    allows the user to run a job much in the way they with mpiexec.  wmpiconfig
    provides a means of setting various global options to the SMPD process
    manager environment.  wmpiregister encrypts the user's credentials and
    saves them to the Windows Registry.

- The following changes have been made to MPE2:

  - MPE2 no longer attempt to compile or link code during 'make install' to
    validate the installation.  Instead, 'make installcheck' may now be used to
    verify that the MPE installation.

  - MPE2 now supports DESTDIR.

- The sock channel now has preliminary support for MPI_THREAD_SERIALIZED and
  MPI_THREAD_MULTIPLE on both UNIX and Microsoft Windows.  We have performed
  rudimentary testing; and while overall the results were very positive, known
  issues do exist.  ROMIO in particular experiences hangs in several places.
  We plan to correct that in the next release.  As always, please report any
  difficulties you encounter.

- Another channel capable of communicating with both over sockets and shared
  memory has been added.  Unlike the ssm channel which waits for new data to
  arrive by continuously polling the system in a busy loop, the essm channel
  waits by blocking on an operating system event object.  This channel is
  experimental, and is only available for Microsoft Windows.

- The topology routines have been modified to allow the device to override the
  default implementation.  This allows the device to export knowledge of the
  underlying physical topology to the MPI routines (Dims_create and the
  reorder == true cases in Cart_create and Graph_create).  

- New memory allocation macros, MPIU_CHK[PL]MEM_*(), have been added to help
  prevent memory leaks.  See mpich2/src/include/mpir_mem.h.

- New error reporting macros, MPIU_ERR_*, have been added to simplify the error
  handling throughout the code, making the code easier to read.  See
  mpich2/src/include/mpir_err.h.

- Interprocess communication using the Sock interface (sock and ssm channels)
  may now be bound to a particular destination interface using the environment
  variable MPICH_INTERFACE_HOSTNAME.  The variable needs to be set for each
  process for which the destination interface is not the default interface.
  (Other mechanisms for destination interface selection will be provided in
  future releases.)  Both MPD and SMPD provide a more simplistic mechanism for
  specifying the interface.  See the user documentation.

- Too many bug fixes to describe.  Much thanks goes to the users who reported
  bugs.  Their patience and understanding as we attempted to recreate the
  problems and solve them is greatly appreciated.


===============================================================================
				Changes in 1.0
===============================================================================

- MPICH2 now works on Solaris.

- The User's Guide has been expanded considerably.  The Installation Guide has
  been expanded some as well.

- MPI_COMM_JOIN has been implemented; although like the other dynamic process
  routines, it is only supported by the Sock channel.

- MPI_COMM_CONNECT and MPI_COMM_ACCEPT are now allowed to connect with remote
  process to which they are already connected.

- Shared libraries can now be built (and used) on IA32 Linux with the GNU
  compilers (--enable-sharedlibs=gcc), and on Solaris with the native Sun
  Workshop compilers (--enable-sharedlibs=solaris).  They may also work on
  other operating systems with GCC, but that has not been tested.  Previous
  restrictions disallowing C++ and Fortran bindings when building shared
  libraries have been removed.

- The dataloop and datatype contents code has been improved to address
  alignment issues on all platforms.

- A bug in the datatype code, which handled zero block length cases
  incorrectly, has been fixed.

- An segmentation fault in the datatype memory management, resulting from
  freeing memory twice, has been fixed.

- The following changes were made to the MPD process manager:

  - MPI_SPAWN_MULTIPLE now works with MPD.

  - The arguments to the 'mpiexec' command supplied by the MPD have changed.
    First, the -default option has been removed.  Second, more flexible ways to
    pass environment variables have been added.

  - The commands 'mpdcheck' and 'testconfig' have been to installations using
    MPD.  These commands test the setup of the machines on which you wish to
    run MPICH2 jobs.  They help to identify misconfiguration, firewall issues,
    and other communication problems.

  - Support for MPI_APPNUM and MPI_UNIVERSE_SIZE has been added to the Simple
    implementation of PMI and the MPD process manager.

  - In general, error detection and recovery in MPD has improved.

- A new process manager, gforker, is now available.  Like the forker process
  manager, gforker spawns processes using fork(), and thus is quite useful on
  SMPs machines.  However, unlike forker, gforker supports all of the features
  of a standard mpiexec, plus some.  Therefore, It should be used in place of
  the previous forker process manager, which is now deprecated.

- The following changes were made to ROMIO:

  - The amount of duplicated ROMIO code in the close, resize, preallocate,
    read, write, asynchronous I/O, and sync routines has been substantially
    reduced.

  - A bug in flattening code, triggered by nested datatypes, has been fixed.

  - Some small memory leaks have been fixed.

  - The error handling has been abstracted allowing different MPI
    implementations to handle and report error conditions in their own way.
    Using this abstraction, the error handling routines have been made
    consistent with rest of MPICH2.

  - AIO support has been cleaned up and unified.  It now works correctly on
    Linux, and is properly detected on old versions of AIX.

  - A bug in MPI_File_seek code, and underlying support code, has been fixed.

  - Support for PVFS2 has improved.

  - Several dead file systems have been removed.  Others, including HFS, SFS,
    PIOFS, and Paragon, have been deprecated.

- MPE and CLOG have been updated to version 2.1. For more details, please see
  src/mpe2/README.

- New macros for memory management were added to support function local
  allocations (alloca), to rollback pending allocations when error conditions
  are detected to avoid memory leaks, and to improve the conciseness of code
  performing memory allocations.

- New error handling macros were added to make internal error handling code
  more concise.

===============================================================================
			       Changes in 0.971
===============================================================================

- Code restricted by copyrights less flexible than the one described in the
  COPYRIGHT file has been removed.

- Installation and User Guides have been added.

- The SMPD PMI Wire Protocol Reference Manual has been updated.

- To eliminate portability problems, common blocks in mpif.h that spanned
  multiple lines were broken up into multiple common blocks each described on a
  single line.

- A new command, mpich2version, was added to allow the user to obtain
  information about the MPICH2 installation.  This command is currently a
  simple shell script.  We anticipate that the mpich2version command will
  eventually provide additional information such as the patches applied and the
  date of the release.

- The following changes were made to MPD2:

  - Support was added for MPI's "singleton init", in which a single
    process started in the normal way (i.e., not by mpiexec or mpirun)
    becomes an MPI process with an MPI_COMM_WORLD of size one by
    calling MPI_Init.  After this the process can call other MPI
    functions, including MPI_Comm_spawn.

  - The format for some of the arguments to mpiexec have changed,
    especially for passing environment variables to MPI processes.

  - In addition to miscellaneous hardening, better error checking and
    messages have been added.

  - The install process has been improved.  In particular, configure
    has been updated to check for a working install program and supply
    it's own installation script (install.sh) if necessary.

  - A new program, mpdcheck, has been added to help diagnose machine
    configurations that might be erroneous or at least confusing to
    mpd.

  - Runtime version checking has been added to insure that the Simple
    implementation of PMI linked into the application and the MPD
    process manager being used to run that application are compatible.

  - Minor improvements have been made to mpdboot.

  - Support for the (now deprecated) BNR interface has been added to
    allow MPICH1 programs to also be run via MPD2.

- Shared libraries are now supported on Linux systems using the GNU compilers
  with the caveat that C++ support must be disabled (--disable-cxx).

- The CH3 interface and device now provide a mechanism for using RDMA (remote
  direct memory access) to transfer data between processes.

- Logging capabilities for MPI and internal routines have been re-added.  See
  the documentation in doc/logging for details.

- A "meminit" option was added to --enable-g to force all bytes associated with
  a structure or union to be initialized prior to use.  This prevents programs
  like Valgrind from complaining about uninitialized accesses.

- The dist-with-version and snap targets in the top-level Makefile.sm now
  properly produce mpich2-<ver>/maint/Version instead of mpich2-<ver>/Version.
  In addition, they now properly update the VERSION variable in Makefile.sm
  without clobbering the sed line that performs the update.

- The dist and snap targets in the top-level Makefile.sm now both use the
  dist-with-version target to avoid inconsistencies.

- The following changes were made to simplemake:

  - The environment variables DEBUG, DEBUG_DIRS, and DEBUG_CONFDIR can now be
    used to control debugging output.

  - Many fixes were made to make simplemake so that it would run cleanly with
    perl -w.

  - Installation of *all* files from a directory is now possible (example,
    installing all of the man pages).

  - The clean targets now remove the cache files produced by newer versions of
    autoconf.

  - For files that are created by configure, the determination of the
    location of that configure has been improved, so that make of those
    files (e.g., make Makefile) is more likely to work.  There is still 
    more to do here.

  - Short loops over subdirectories are now unrolled.

  - The maintainerclean target has been renamed to maintainer-clean to match
    GNU guidelines.

  - The distclean and maintainer-clean targets have been improved.

  - An option was added to perform one ar command per directory instead of one
    per file when creating the profiling version of routines (needed only for
    systems that do not support weak symbols).


===============================================================================
				Changes in 0.97
===============================================================================

- MPI-2 one-sided communication has been implemented in the CH3 device.

- mpigdb works as a simple parallel debugger for MPI programs started
  with mpd.  New since MPICH1 is the ability to attach to running
  parallel programs.  See the README in mpich2/src/pm/mpd for details.

- MPI_Type_create_darray() and MPI_Type_create_subarray() implemented including
  the right contents and envelope data.

- ROMIO flattening code now supports subarray and darray combiners.

- Improve scalability and performance of some ROMIO PVFS and PVFS2 routines 

- An error message string parameter was added to MPID_Abort().  If the
  parameter is non-NULL this string will be used as the message with the abort
  output.  Otherwise, the output message will be base on the error message
  associated with the mpi_errno parameter.

- MPID_Segment_init() now takes an additional boolean parameter that specifies
  if the segment processing code is to produce/consume homogeneous (FALSE) or
  heterogeneous (TRUE) data.

- The definitions of MPID_VCR and MPID_VCRT are now defined by the device.

- The semantics of MPID_Progress_{Start,Wait,End}() have changed.  A typical
  blocking progress loop now looks like the following.

  if (req->cc != 0)
  {
      MPID_Progress_state progress_state;

      MPID_Progress_start(&progress_state);
      while (req->cc != 0)
      {
          mpi_errno = MPID_Progress_wait(&progress_state);
          if (mpi_errno != MPI_SUCCESS)
          {
              /* --BEGIN ERROR HANDLING-- */
              MPID_Progress_end(&progress_state);
              goto fn_fail;
              /* --END ERROR HANDLING-- */
          }
      }
      MPID_Progress_end(&progress_state);
  }

  NOTE: each of these routines now takes a single parameter, a pointer to a
  thread local state variable.

- The CH3 device and interface have been modified to better support
  MPI_COMM_{SPAWN,SPAWN_MULTIPLE,CONNECT,ACCEPT,DISCONNECT}.  Channels
  writers will notice the following.  (This is still a work in progress.  See
  the note below.)

  - The introduction of a process group object (MPIDI_PG_t) and a new
    set of routines to manipulate that object.

  - The renaming of the MPIDI_VC object to MPIDI_VC_t to make it more
    consistent with the naming of other objects in the device.

  - The process group information in the MPIDI_VC_t moved from the channel
    specific portion to the device layer.

  - MPIDI_CH3_Connection_terminate() was added to the CH3 interface to allow
    the channel to properly shutdown a connection before the device deletes all
    associated data structures.

  - A new upcall routine, MPIDI_CH3_Handle_connection(), was added to allow the
    device to notify the device when a connection related event has completed.
    A present the only event is MPIDI_CH3_VC_EVENT_TERMINATED, which notify the
    device that the underlying connection associated with a VC has been
    properly shutdown.  For every call to MPIDI_CH3_Connection_terminate() that
    the device makes, the channel must make a corresponding upcall to
    MPIDI_CH3_Handle_connection().  MPID_Finalize() will likely hang if this
    rule is not followed.

  - MPIDI_CH3_Get_parent_port() was added to provide MPID_Init() with the port
    name of the the parent (spawner).  This port name is used by MPID_Init()
    and MPID_Comm_connect() to create an intercommunicator between the parent
    (spawner) and child (spawnee).  Eventually, MPID_Comm_spawn_multiple() will
    be update to perform the reverse logic; however, the logic is presently
    still in the sock channel.

  Note: the changes noted are relatively fresh and are the beginning to a set
  of future changes.  The goal is to minimize the amount of code required by a
  channel to support MPI dynamic process functionality.  As such, portions of
  the device will change dramatically in a future release.  A few more changes
  to the CH3 interface are also quite likely.

- MPIDI_CH3_{iRead,iWrite}() have been removed from the CH3 interface.
  MPIDI_CH3U_Handle_recv_pkt() now returns a receive request with a populated
  iovec to receive data associated with the request.
  MPIDU_CH3U_Handle_{recv,send}_req() reload the iovec in the request and
  return and set the complete argument to TRUE if more data is to read or
  written.  If data transfer for the request is complete, the complete argument
  must be set to FALSE.


=============================================================================== 
                               Changes in 0.96p2
===============================================================================

The shm and ssm channels have been added back into the distribution.
Officially, these channels are supported only on x86 platforms using the gcc
compiler.  The necessary assembly instructions to guarantee proper ordering of
memory operations are lacking for other platforms and compilers.  That said, we
have seen a high success rate when testing these channels on unsupported
systems.

This patch release also includes a new unsupported channel.  The scalable
shared memory, or sshm, channel is similar to the shm channel except that it
allocates shared memory communication queues only when necessary instead of
preallocating N-squared queues.


===============================================================================
                               Changes in 0.96p1
===============================================================================

This patch release fixes a problem with building MPICH2 on Microsoft Windows
platforms.  It also corrects a serious bug in the poll implementation of the
Sock interface.


===============================================================================
                                Changes in 0.96
===============================================================================

The 0.96 distribution is largely a bug fix release.  In addition to the many
bug fixes, major improvements have been made to the code that supports the
dynamic process management routines (MPI_Comm_{connect,accept,spawn,...}()).
Additional changes are still required to support MPI_Comm_disconnect().

We also added an experimental (and thus completely unsupported) rdma device.
The internal interface is similar to the CH3 interface except that it contains
a couple of extra routines to inform the device about data transfers using the
rendezvous protocol.  The channel can use this extra information to pin memory
and perform a zero-copy transfer.  If all goes well, the results will be rolled
back into the CH3 device.

Due to last minute difficulties, this release does not contain the shm or ssm
channels.  These channels will be included in a subsequent patch release.


===============================================================================
				Changes in 0.94
===============================================================================

Active target one-sided communication is now available for the ch3:sock
channel.  This new functionality has undergone some correctness testing but has
not been optimized in terms of performance.  Future release will include
performance enhancements, passive target communication, and availability in
channels other than just ch3:sock.

The shared memory channel (ch3:shm), which performs communication using shared
memory on a single machine, is now complete and has been extensively tested.
At present, this channel only supports IA32 based machines (excluding the
Pentium Pro which has a memory ordering bug).  In addition, this channel must
be compiled with gcc.  Future releases with support additional architectures
and compilers.

A new channel has been added that performs inter-node communication using
sockets (TCP/IP) and intra-node communication using shared memory.  This
channel, ch3:ssm, is ideal for clusters of SMPs.  Like the shared memory
channel (ch3:shm), this channel only supports IA32 based machines and must be
compiled with gcc.  In future releases, the ch3:ssm channel will support
additional architectures and compilers.

The two channels that perform commutation using shared memory, ch3:shm and
ch3:ssm, now support the allocation of shared memory using both the POSIX and
System V interfaces.  The POSIX interface will be used if available; otherwise,
the System V interface is used.

In the interest of increasing portability, many enhancements have been made to
both the code and the configure scripts.

And, as always, many bugs have been fixed :-).


***** INTERFACE CHANGES ****

The parameters to MPID_Abort() have changed.  MPID_Abort() now takes a pointer
to communicator object, an MPI error code, and an exit code.

MPIDI_CH3_Progress() has been split into two functions:
 MPIDI_CH3_Progress_wait() and MPIDI_CH3_Progress_test().


===============================================================================
				Changes in 0.93
===============================================================================

Version 0.93 has undergone extensive changes to provide better error reporting.
Part of these changes involved modifications to the ADI3 and CH3 interfaces.
The following routines now return MPI error codes:

MPID_Cancel_send()
MPID_Cancel_recv()
MPID_Progress_poke()
MPID_Progress_test()
MPID_Progress_wait()
MPIDI_CH3_Cancel_send()
MPIDI_CH3_Progress()
MPIDI_CH3_Progress_poke()
MPIDI_CH3_iRead()
MPIDI_CH3_iSend()
MPIDI_CH3_iSendv()
MPIDI_CH3_iStartmsg()
MPIDI_CH3_iStartmsgv()
MPIDI_CH3_iWrite()
MPIDI_CH3U_Handle_recv_pkt()
MPIDI_CH3U_Handle_recv_req()
MPIDI_CH3U_Handle_send_req()

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Of special note are MPID_Progress_test(), MPID_Progress_wait() and
MPIDI_CH3_Progress() which previously returned an integer value indicating if
one or more requests had completed.  They no longer return this value and
instead return an MPI error code (also an integer).  The implication being that
while the semantics changed, the type signatures did not.
*******************************************************************************

The function used to create error codes, MPIR_Err_create_code(), has also
changed.  It now takes additional parameters, allowing it create a stack of
errors and making it possible for the reporting function to indicate in which
function and on which line the error occurred.  It also allows an error to be
designated as fatal or recoverable.  Fatal errors always result in program
termination regardless of the error handler installed by the application.

A RDMA channel has been added and includes communication methods for shared
memory and shmem.  This is recent development and the RDMA interface is still
in flux.