			MPICH Release 3.0.4

MPICH is a high-performance and widely portable implementation of the
MPI-3.0 standard from the Argonne National Laboratory.  This release
has all MPI 3.0 functions and features required by the standard with
the exception of support for the "external32" portable I/O format and
user-defined data representations for I/O.

This README file should contain enough information to get you started
with MPICH. More extensive installation and user guides can be found
in the doc/installguide/install.pdf and doc/userguide/user.pdf files
respectively. Additional information regarding the contents of the
release can be found in the CHANGES file in the top-level directory,
and in the RELEASE_NOTES file, where certain restrictions are
detailed. Finally, the MPICH web site,
http://www.mcs.anl.gov/research/projects/mpich, contains information
on bug fixes and new releases.


1.  Getting Started
2.  Reporting Installation or Usage Problems
3.  Compiler Flags
4.  Alternate Channels and Devices
5.  Alternate Process Managers
6.  Alternate Configure Options
7.  Testing the MPICH installation
8.  Fault Tolerance
9.  Environment Variables
10. Developer Builds
11. Installing MPICH on windows
12. Multiple Fortran compiler support


-------------------------------------------------------------------------

1. Getting Started
==================

The following instructions take you through a sequence of steps to get
the default configuration (ch3 device, nemesis channel (with TCP and
shared memory), Hydra process management) of MPICH up and running.

(a) You will need the following prerequisites.

    - REQUIRED: This tar file mpich-3.0.4.tar.gz

    - REQUIRED: A C compiler (gcc is sufficient)

    - OPTIONAL: A C++ compiler, if C++ applications are to be used
      (g++, etc.). If you do not require support for C++ applications,
      you can disable this support using the configure option
      --disable-cxx (configuring MPICH is described in step 1(d)
      below).

    - OPTIONAL: A Fortran 77 compiler, if Fortran 77 applications are
      to be used (gfortran, ifort, etc.). If you do not require
      support for Fortran 77 applications, you can disable this
      support using --disable-f77 (configuring MPICH is described in
      step 1(d) below).

    - OPTIONAL: A Fortran 90 compiler, if Fortran 90 applications are
      to be used (gfortran, ifort, etc.). If you do not require
      support for Fortran 90 applications, you can disable this
      support using --disable-fc. Note that Fortran 77 support is a
      prerequisite for Fortran 90 support (configuring MPICH is
      described in step 1(d) below).

    Also, you need to know what shell you are using since different shell
    has different command syntax. Command "echo $SHELL" prints out the
    current shell used by your terminal program.

(b) Unpack the tar file and go to the top level directory:

      tar xzf mpich-3.0.4.tar.gz
      cd mpich-3.0.4

    If your tar doesn't accept the z option, use

      gunzip mpich-3.0.4.tar.gz
      tar xf mpich-3.0.4.tar
      cd mpich-3.0.4

(c) Choose an installation directory, say
    /home/<USERNAME>/mpich-install, which is assumed to non-existent
    or empty. It will be most convenient if this directory is shared
    by all of the machines where you intend to run processes. If not,
    you will have to duplicate it on the other machines after
    installation.

(d) Configure MPICH specifying the installation directory:

    for csh and tcsh:

      ./configure --prefix=/home/<USERNAME>/mpich-install |& tee c.txt

    for bash and sh:

      ./configure --prefix=/home/<USERNAME>/mpich-install 2>&1 | tee c.txt

    Bourne-like shells, sh and bash, accept "2>&1 |".  Csh-like shell,
    csh and tcsh, accept "|&". If a failure occurs, the configure
    command will display the error. Most errors are straight-forward
    to follow. For example, if the configure command fails with:

       "No Fortran 77 compiler found. If you don't need to build any
        Fortran programs, you can disable Fortran support using
        --disable-f77 and --disable-fc. If you do want to build
        Fortran programs, you need to install a Fortran compiler such
        as gfortran or ifort before you can proceed."

    ... it means that you don't have a Fortran compiler :-). You will
    need to either install one, or disable Fortran support in MPICH.

    If you are unable to understand what went wrong, please go to step
    (2) below, for reporting the issue to the MPICH developers and
    other users.

(e) Build MPICH:

    for csh and tcsh:

      make |& tee m.txt

    for bash and sh:

      make 2>&1 | tee m.txt

    This step should succeed if there were no problems with the
    preceding step. Check file m.txt. If there were problems, do a
    "make clean" and then run make again with V=1.

      make V=1 |& tee m.txt       (for csh and tcsh)

      OR

      make V=1 2>&1 | tee m.txt   (for bash and sh)

    Then go to step (2) below, for reporting the issue to the MPICH
    developers and other users.

(f) Install the MPICH commands:

    for csh and tcsh:

      make install |& tee mi.txt

    for bash and sh:

      make install 2>&1 | tee mi.txt

    This step collects all required executables and scripts in the bin
    subdirectory of the directory specified by the prefix argument to
    configure.

(g) Add the bin subdirectory of the installation directory to your
    path in your startup script (.bashrc for bash, .cshrc for csh,
    etc.):

    for csh and tcsh:

      setenv PATH /home/<USERNAME>/mpich-install/bin:$PATH

    for bash and sh:
  
      PATH=/home/<USERNAME>/mpich-install/bin:$PATH ; export PATH

    Check that everything is in order at this point by doing:

      which mpicc
      which mpiexec

    These commands should display the path to your bin subdirectory of
    your install directory.

    IMPORTANT NOTE: The install directory has to be visible at exactly
    the same path on all machines you want to run your applications
    on. This is typically achieved by installing MPICH on a shared
    NFS file-system. If you do not have a shared NFS directory, you
    will need to manually copy the install directory to all machines
    at exactly the same location.

(h) MPICH uses a process manager for starting MPI applications. The
    process manager provides the "mpiexec" executable, together with
    other utility executables. MPICH comes packaged with multiple
    process managers; the default is called Hydra.

    Now we will run an MPI job, using the mpiexec command as specified
    in the MPI standard. There are some examples in the install
    directory, which you have already put in your path, as well as in
    the directory mpich-3.0.4/examples. One of them is the classic
    CPI example, which computes the value of pi by numerical
    integration in parallel.

    To run the CPI example with 'n' processes on your local machine,
    you can use:

      mpiexec -n <number> ./examples/cpi

    Test that you can run an 'n' process CPI job on multiple nodes:

      mpiexec -f machinefile -n <number> ./examples/cpi

    The 'machinefile' is of the form:

      host1
      host2:2
      host3:4   # Random comments
      host4:1

    'host1', 'host2', 'host3' and 'host4' are the hostnames of the
    machines you want to run the job on. The ':2', ':4', ':1' segments
    depict the number of processes you want to run on each node. If
    nothing is specified, ':1' is assumed.

    More details on interacting with Hydra can be found at
    http://wiki.mpich.org/mpich/index.php/Using_the_Hydra_Process_Manager

If you have completed all of the above steps, you have successfully
installed MPICH and run an MPI example.

-------------------------------------------------------------------------

2. Reporting Installation or Usage Problems
===========================================

[VERY IMPORTANT: PLEASE COMPRESS ALL FILES BEFORE SENDING THEM TO
US. DO NOT SPAM THE MAILING LIST WITH LARGE ATTACHMENTS.]

The distribution has been tested by us on a variety of machines in our
environments as well as our partner institutes. If you have problems
with the installation or usage of MPICH, please follow these steps:

1. First see the Frequently Asked Questions (FAQ) page at
http://wiki.mpich.org/mpich/index.php/Frequently_Asked_Questions to
see if the problem you are facing has a simple solution. Many common
problems and their solutions are listed here.

2. If you cannot find an answer on the FAQ page, look through previous
email threads on the mpich-discuss mailing list archive
(http://lists.mcs.anl.gov/pipermail/mpich-discuss/). It is likely
someone else had a similar problem, which has already been resolved
before.

3. If neither of the above steps work, please send an email to
mpich-discuss@mcs.anl.gov. You need to subscribe to this list
(https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss) before
sending an email.

Your email should contain the following files.  ONCE AGAIN, PLEASE
COMPRESS BEFORE SENDING, AS THE FILES CAN BE LARGE.  Note that,
depending on which step the build failed, some of the files might not
exist.

    mpich-3.0.4/c.txt (generated in step 1(d) above)
    mpich-3.0.4/m.txt (generated in step 1(e) above)
    mpich-3.0.4/mi.txt (generated in step 1(f) above)
    mpich-3.0.4/config.log (generated in step 1(d) above)
    mpich-3.0.4/src/openpa/config.log (generated in step 1(d) above)
    mpich-3.0.4/src/mpl/config.log (generated in step 1(d) above)
    mpich-3.0.4/src/pm/hydra/config.log (generated in step 1(d) above)
    mpich-3.0.4/src/pm/hydra/tools/topo/hwloc/hwloc/config.log (generated in step 1(d) above)

    DID WE MENTION? DO NOT FORGET TO COMPRESS THESE FILES!

If you have compiled MPICH and are having trouble running an
application, please provide the output of the following command in
your email.

    mpiexec -info

Finally, please include the actual error you are seeing when running
the application, including the mpiexec command used, and the host
file. If possible, please try to reproduce the error with a smaller
application or benchmark and send that along in your bug report.

4. If you have found a bug in MPICH, we request that you report it at
our bug tracking system:
(https://trac.mpich.org/projects/mpich/newticket). Even if you
believe you have found a bug, we recommend you sending an email to
mpich-discuss@mcs.anl.gov first.


-------------------------------------------------------------------------

3. Compiler Flags
=================

MPICH allows several sets of compiler flags to be used. The first
three sets are configure-time options for MPICH, while the fourth is
only relevant when compiling applications with mpicc and friends.

(a) CFLAGS, CPPFLAGS, CXXFLAGS, FFLAGS, FCFLAGS, LDFLAGS and LIBS
(abbreviated as xFLAGS): Setting these flags would result in the
MPICH library being compiled/linked with these flags and the flags
internally being used in mpicc and friends.

(b) MPICHLIB_CFLAGS, MPICHLIB_CPPFLAGS, MPICHLIB_CXXFLAGS,
MPICHLIB_FFLAGS, MPICHLIB_FCFLAGS, MPICHLIB_LDFLAGS and
MPICHLIB_LIBS (abbreviated as MPICHLIB_xFLAGS): Setting these flags
would result in the MPICH library being compiled/linked with these
flags. However, these flags will *not* be used by mpicc and friends.

(c) MPICH_MAKE_CFLAGS: Setting these flags would result in MPICH's
configure tests to not use these flags, but the makefile's to use
them. This is a temporary hack for certain cases that advanced
developers might be interested in, but which break existing configure
tests (e.g., -Werror). These are NOT recommended for regular users.

(d) MPICH_MPICC_FLAGS, MPICH_MPICPP_FLAGS, MPICH_MPICXX_FLAGS,
MPICH_MPIF77_FLAGS, MPICH_MPIFC_FLAGS, MPICH_LDFLAGS and
MPICH_LIBS (abbreviated as MPICH_MPIX_FLAGS): These flags do *not*
affect the compilation of the MPICH library itself, but will be
internally used by mpicc and friends.


  +--------------------------------------------------------------------+
  |                    |                      |                        |
  |                    |    MPICH library     |    mpicc and friends   |
  |                    |                      |                        |
  +--------------------+----------------------+------------------------+
  |                    |                      |                        |
  |     xFLAGS         |         Yes          |           Yes          |
  |                    |                      |                        |
  +--------------------+----------------------+------------------------+
  |                    |                      |                        |
  |  MPICHLIB_xFLAGS   |         Yes          |           No           |
  |                    |                      |                        |
  +--------------------+----------------------+------------------------+
  |                    |                      |                        |
  | MPICH_MAKE_xFLAGS  |         Yes          |           No           |
  |                    |                      |                        |
  +--------------------+----------------------+------------------------+
  |                    |                      |                        |
  | MPICH_MPIX_FLAGS   |         No           |           Yes          |
  |                    |                      |                        |
  +--------------------+----------------------+------------------------+


All these flags can be set as part of configure command or through
environment variables.


Default flags
--------------
By default, MPICH automatically adds certain compiler optimizations
to MPICHLIB_CFLAGS. The currently used optimization level is -O2.

** IMPORTANT NOTE: Remember that this only affects the compilation of
the MPICH library and is not used in the wrappers (mpicc and friends)
that are used to compile your applications or other libraries.

This optimization level can be changed with the --enable-fast option
passed to configure. For example, to build an MPICH environment with
-O3 for all language bindings, one can simply do:

  ./configure --enable-fast=O3

Or to disable all compiler optimizations, one can do:

  ./configure --disable-fast

For more details of --enable-fast, see the output of "configure
--help".


Examples
--------

Example 1:

  ./configure --disable-fast MPICHLIB_CFLAGS=-O3 MPICHLIB_FFLAGS=-O3 \
        MPICHLIB_CXXFLAGS=-O3 MPICHLIB_FCFLAGS=-O3

This will cause the MPICH libraries to be built with -O3, and -O3
will *not* be included in the mpicc and other MPI wrapper script.

Example 2:

  ./configure --disable-fast CFLAGS=-O3 FFLAGS=-O3 CXXFLAGS=-O3 FCFLAGS=-O3

This will cause the MPICH libraries to be built with -O3, and -O3
will be included in the mpicc and other MPI wrapper script.

Example 3:

There are certain compiler flags that should not be used with MPICH's
configure, e.g. gcc's -Werror, which would confuse configure and cause
certain configure tests to fail to detect the correct system features.
To use -Werror in building MPICH libraries, you can pass the compiler
flags during the make step through the Makefile variable
MPICH_MAKE_CFLAGS as follows:

  make MPICH_MAKE_CFLAGS="-Wall -Werror"

The content of MPICH_MAKE_CFLAGS is appended to the CFLAGS in all
relevant Makefiles.

-------------------------------------------------------------------------

4. Alternate Channels and Devices
=================================

The communication mechanisms in MPICH are called "devices". MPICH
supports ch3 (default), as well as many third-party devices that are
released and maintained by other institutes such as osu_ch3 (from Ohio
State University for InfiniBand and iWARP), ch_mx (from Myricom for
Myrinet MX), etc.

                   *************************************

ch3 device
**********
The ch3 device contains different internal communication options
called "channels". We currently support nemesis (default) and sock
channels.

nemesis channel
---------------
Nemesis provides communication using different networks (tcp, mx) as
well as various shared-memory optimizations. To configure MPICH with
nemesis, you can use the following configure option:

  --with-device=ch3:nemesis

The TCP network module gets configured in by default. To specify a
different network module such as MX, you can use:

  --with-device=ch3:nemesis:mx

If the MX include files and libraries are not in the normal search
paths, you can specify them with the following options:

  --with-mx-include= and --with-mx-lib=

... or the if lib/ and include/ are in the same directory, you can use
the following option:

  --with-mx=

If the MX libraries are shared libraries, they need to be in the
shared library search path. This can be done by adding the path to
/etc/ld.so.conf, or by setting the LD_LIBRARY_PATH variable in your
.bashrc (or .tcshrc) file.  It's also possible to set the shared
library search path in the binary. If you're using gcc, you can do
this by adding

  LD_LIBRARY_PATH=/path/to/lib

  (and)

  LDFLAGS="-Wl,-rpath -Wl,/path/to/lib"

... as arguments to configure.

By default, MX allows for only eight endpoints per node causing
ch3:nemesis:mx to give initialization errors with greater than 8
processes on the same node (this is an MX error and not an inherent
limitation in the MPICH/Nemesis design). If needed, this can be set
to a higher number when MX is loaded. We recommend the user to contact
help@myri.com for details on how to do this.

Shared-memory optimizations are enabled by default to improve
performance for multi-processor/multi-core platforms. They can be
disabled (at the cost of performance) either by setting the
environment variable MPICH_NO_LOCAL to 1, or using the following
configure option:

  --enable-nemesis-dbg-nolocal

The --with-shared-memory= configure option allows you to choose how
Nemesis allocates shared memory.  The options are "auto", "sysv", and
"mmap".  Using "sysv" will allocate shared memory using the System V
shmget(), shmat(), etc. functions.  Using "mmap" will allocate shared
memory by creating a file (in /dev/shm if it exists, otherwise /tmp),
then mmap() the file.  The default is "auto". Note that System V
shared memory has limits on the size of shared memory segments so
using this for Nemesis may limit the number of processes that can be
started on a single node.

sock channel
------------
sock is the traditional TCP sockets based communication channel. It
uses TCP/IP sockets for all communication including intra-node
communication. So, though the performance of this channel is worse
than that of nemesis, it should work on almost every platform. This
channel can be configured using the following option:

  --with-device=ch3:sock


pamid device
************
This is the device used on the IBM Blue Gene/Q system.  The following
configure options can be used:

  ./configure --host=powerpc64-bgq-linux --target=powerpc64-bgq-linux --build=powerpc64-linux-gnu
	      --with-device=pamid:BGQ --with-file-system=bg+bglockless --enable-timer-type=device
	      --with-fwrapname=fmpich --with-cross=src/mpid/pamid/cross/bgq8
	      --with-pm=none --enable-timing=no --disable-collchk
	      --disable-graphics --disable-rlog --disable-sample --disable-rpath
	      --with-aint-size=8 --with-assert-level=2 --enable-fast=O3
	      --enable-error-messages --disable-debuginfo
	      --enable-thread-cs=per-object --enable-handle-allocation=tls
	      --enable-refcount=lock-free --disable-predefined-refcount
	      CC=powerpc64-bgq-linux-gcc
	      CXX=powerpc64-bgq-linux-g++
	      F77=powerpc64-bgq-linux-gfortran
	      FC=powerpc64-bgq-linux-gfortran

-------------------------------------------------------------------------

5. Alternate Process Managers
=============================

hydra
-----
Hydra is the default process management framework that uses existing
daemons on nodes (e.g., ssh, pbs, slurm, sge) to start MPI
processes. More information on Hydra can be found at
http://wiki.mpich.org/mpich/index.php/Using_the_Hydra_Process_Manager

mpd
---
MPD was the traditional process manager in MPICH. The file
mpich-3.0.4/src/pm/mpd/README has more information about
interactive commands for managing the ring of MPDs. The MPD process
manager is now deprecated.

smpd
---- 
SMPD is a process manager for interoperability between Microsoft
Windows and UNIX, where some processes are running on Windows and
others are running on a variant of UNIX. For more information, please
see mpich-3.0.4/src/pm/smpd/README.

gforker
-------
gforker is a process manager that creates processes on a single
machine, by having mpiexec directly fork and exec them. gforker is
mostly meant as a research platform and for debugging purposes, as it
is only meant for single-node systems.

slurm
-----
SLURM is an external process manager not distributed with
MPICH. MPICH's default process manager, hydra, has native support
for slurm and you can directly use it in slurm environments (it will
automatically detect slurm and use slurm capabilities). However, if
you want to use the slurm provided "srun" process manager, you can use
the "--with-pmi=slurm --with-pm=no" option with configure. Note that
the "srun" process manager that comes with slurm uses an older PMI
standard which does not have some of the performance enhancements that
hydra provides in slurm environments.

-------------------------------------------------------------------------

6. Alternate Configure Options
==============================

MPICH has a number of other features. If you are exploring MPICH as
part of a development project, you might want to tweak the MPICH
build with the following configure options. A complete list of
configuration options can be found using:

   ./configure --help

However, for your convenience, we list a few important options here:

Performance Options:

 --enable-fast - Turns off error checking and collection of internal
                 timing information

 --enable-timing=no - Turns off just the collection of internal timing
                      information

 --enable-ndebug - Turns on NDEBUG, which disables asserts. This is a
                   subset of the optimizations provided by
                   enable-fast, but is useful in environments where
                   the user wishes to retain the debug symbols, e.g.,
                   this can be combined with the --enable-g option.

MPI Features:

  --enable-romio - Build the ROMIO implementation of MPI-IO (enabled
                   by default).

  --with-file-system - When used with --enable-romio, specifies
                       filesystems ROMIO should support. They can be
                       specified by passing them in a '+'-delimited
                       list: (e.g.,
                       --with-file-system="pvfs+nfs+ufs").

                       If you have installed version 2 of the PVFS
                       file system, you can use the
                       '--with-pvfs2=<prefix>' configure option to
                       specify where libraries, headers, and utilities
                       have been installed. If you have added the pvfs
                       utilities to your PATH, then ROMIO will detect
                       this and build support for PVFS automatically.

  --enable-threads - Build MPICH with support for multi-threaded
                     applications. Only the sock and nemesis channels
                     support MPI_THREAD_MULTIPLE.

  --with-thread-package - When used with --enable-threads, this option
                          specifies the thread package to use.  This
                          option defaults to "posix".  At the moment,
                          only POSIX threads are supported on UNIX
                          platforms.  We plan to support Solaris
                          threads in the future.

Language bindings:

  --enable-f77 - Build the Fortran 77 bindings (enabled by default).

  --enable-fc - Build the Fortran 90 bindings (enabled by default).

  --enable-cxx - Build the C++ bindings (enabled by default).

Shared library support:

  --enable-shared - Enable shared library support.  Note that "rpath"
                    linking is used by default in stock MPICH
                    distributions.  Re-running ./autogen.sh with a
                    patched libtool can eliminate rpath usage.  See
                    http://wiki.debian.org/RpathIssue for more info.

Cross compilation:

  --with-cross=filename - Provide values for the tests that required
                          running a program, such as the tests that
                          configure uses to determine the sizes of the
                          basic types.  This should be a fine in
                          Bourne shell format containing variable
                          assignment of the form

                          CROSS_SIZEOF_INT=2

                          for all of the CROSS_xxx variables.

Error checking and reporting:

  --enable-error-checking=level - Control the amount of error
                                  checking. Currently, only "no" and
                                  "all" is supported; all is the
                                  default.

  --enable-error-messages=level - Control the aount of detail in error
                                  messages. By default, MPICH
                                  provides instance-specific error
                                  messages; but, with this option,
                                  MPICH can be configured to provide
                                  less detailed messages.  This may be
                                  desirable on small systems, such as
                                  clusters built from game consoles or
                                  high-density massively parallel
                                  systems.  This is still under active
                                  development.

Compilation options for development:

  --enable-g=value - Controls the amount of debugging information
                     collected by the code.  The most useful choice
                     here is dbg, which compiles with -g.

  --enable-coverage - An experimental option that enables GNU coverage
                      analysis.

  --with-logging=name - Select a logging library for recording the
                        timings of the internal routines.  We have
                        used this to understand the performance of the
                        internals of MPICH.  More information on the
                        logging options, capabilities and usage can be
                        found in doc/logging/logging.pdf.

  --enable-timer-type=name - Select the timer to use for MPI_Wtime and
                             internal timestamps.  name may be one of:
                     gethrtime        - Solaris timer (Solaris systems
                                        only) 
                     clock_gettime    - Posix timer (where available)
                     gettimeofday     - Most Unix systems
                     linux86_cycle    - Linux x86; returns cycle
                                        counts, not time in seconds*
                     linuxalpha_cycle - Like linux86_cycle, but for
                                        Linux Alpha* 
                     gcc_ia64_cycle   - IPF ar.itc timer*
                     device           - The timer is provided by the device
                 *Note that the cycle timers are intended to be used by
                  MPICH developers for internal low-level timing.
                  Normal users should not use these as they are not
                  guaranteed to be accurate in certain situations.

-------------------------------------------------------------------------

7. Testing the MPICH installation
==================================

To test MPICH, we package the MPICH test suite in the MPICH
distribution. You can run the test suite using:

     make testing

The results summary will be placed in test/summary.xml

-------------------------------------------------------------------------

8. Fault Tolerance
==================

MPICH has some tolerance to process failures, and supports
checkpointing and restart. 

Tolerance to Process Failures
-----------------------------

The features described in this section should be considered
experimental.  Which means that they have not been fully tested, and
the behavior may change in future releases. The below notes are some
guidelines on what can be expected in this feature:

 - ERROR RETURNS: Communication failures in MPICH are not fatal
   errors.  This means that if the user sets the error handler to
   MPI_ERRORS_RETURN, MPICH will return an appropriate error code in
   the event of a communication failure.  When a process detects a
   failure when communicating with another process, it will consider
   the other process as having failed and will no longer attempt to
   communicate with that process.  The user can, however, continue
   making communication calls to other processes.  Any outstanding
   send or receive operations to a failed process, or wildcard
   receives (i.e., with MPI_ANY_SOURCE) posted to communicators with a
   failed process, will be immediately completed with an appropriate
   error code.

 - COLLECTIVES: For collective operations performed on communicators
   with a failed process, the collective would return an error on
   some, but not necessarily all processes. A collective call
   returning MPI_SUCCESS on a given process means that the part of the
   collective performed by that process has been successful.

 - PROCESS MANAGER: If used with the hydra process manager, hydra will
   detect failed processes and notify the MPICH library.  Users can
   query the list of failed processes using MPIX_Comm_group_failed().
   This functions returns a group consisting of the failed processes
   in the communicator.  The function MPIX_Comm_remote_group_failed()
   is provided for querying failed processes in the remote processes
   of an intercommunicator.

   Note that hydra by default will abort the entire application when
   any process terminates before calling MPI_Finalize.  In order to
   allow an application to continue running despite failed processes,
   you will need to pass the -disable-auto-cleanup option to mpiexec.

 - FAILURE NOTIFICATION: THIS IS AN UNSUPPORTED FEATURE AND WILL
   ALMOST CERTAINLY CHANGE IN THE FUTURE!

   In the current release, hydra notifies the MPICH library of failed
   processes by sending a SIGUSR1 signal.  The application can catch
   this signal to be notified of failed processes.  If the application
   replaces the library's signal handler with its own, the application
   must be sure to call the library's handler from it's own
   handler.  Note that you cannot call any MPI function from inside a
   signal handler.

Checkpoint and Restart
----------------------

MPICH supports checkpointing and restart fault-tolerance using BLCR.

CONFIGURATION

First, you need to have BLCR version 0.8.2 or later installed on your
machine.  If it's installed in the default system location, you don't
need to do anything.

If BLCR is not installed in the default system location, you'll need
to tell MPICH's configure where to find it. You might also need to
set the LD_LIBRARY_PATH environment variable so that BLCR's shared
libraries can be found.  In this case add the following options to
your configure command:

  --with-blcr=<BLCR_INSTALL_DIR> 
  LD_LIBRARY_PATH=<BLCR_INSTALL_DIR>/lib

where <BLCR_INSTALL_DIR> is the directory where BLCR has been
installed (whatever was specified in --prefix when BLCR was
configured).

After it's configured compile as usual (e.g., make; make install).

Note, checkpointing is only supported with the Hydra process manager.


VERIFYING CHECKPOINTING SUPPORT

Make sure MPICH is correctly configured with BLCR. You can do this
using:

  mpiexec -info

This should display 'BLCR' under 'Checkpointing libraries available'.


CHECKPOINTING THE APPLICATION

There are two ways to cause the application to checkpoint. You can ask
mpiexec to periodically checkpoint the application using the mpiexec
option -ckpoint-interval (seconds):

  mpiexec -ckpointlib blcr -ckpoint-prefix /tmp/app.ckpoint \
      -ckpoint-interval 3600 -f hosts -n 4 ./app

Alternatively, you can also manually force checkpointing by sending a
SIGUSR1 signal to mpiexec.

The checkpoint/restart parameters can also be controlled with the
environment variables HYDRA_CKPOINTLIB, HYDRA_CKPOINT_PREFIX and
HYDRA_CKPOINT_INTERVAL.

To restart a process:

  mpiexec -ckpointlib blcr -ckpoint-prefix /tmp/app.ckpoint -f hosts -n 4 -ckpoint-num <N>

where <N> is the checkpoint number you want to restart from.

These instructions can also be found on the MPICH wiki:

  http://wiki.mpich.org/mpich/index.php/Checkpointing

-------------------------------------------------------------------------

9. Environment Variables
========================

MPICH provides several environment variables that have different
purposes. Many of these environment variables are listed in the
README.envvar file. Some more are listed below.

  MPICH_ASYNC_PROGRESS - Initiates a spare thread to provide
         asynchronous progress. This improves progress semantics for
         all MPI operations including point-to-point, collective,
         one-sided operations and I/O. Setting this variable would
         increase the thread-safety level to
         MPI_THREAD_MULTIPLE. While this improves the progress
         semantics, it might cause a small amount of performance
         overhead for regular MPI operations.

               ************************************

  MPICH_NAMEPUB_DIR - Allows the user to override where the publish
         and lookup information is placed for connect/accept based
         applications.

-------------------------------------------------------------------------

10. Developer Builds
====================
For MPICH developers who want to directly work on the svn, there are
a few additional steps involved (people using the release tarballs do
not have to follow these steps). Details about these steps can be
found here:
http://wiki.mpich.org/mpich/index.php/Getting_And_Building_MPICH

-------------------------------------------------------------------------

11. Installing MPICH on Windows
================================

Here are the instructions for setting up MPICH on a Windows machine:

(a) Install:
    Microsoft Developer Studio 2003 or later
    Intel Fortran 8.0 or later
    cygwin
	choose the dos file format option
	install perl and svn

(b) Checkout mpich:

    Bring up a command prompt.
    (replace "yourname" with your MCS login name):
    svn co https://svn.mcs.anl.gov/repos/mpi/mpich2/trunk mpich

(c) Generate *.h.in

    Bring up a cygwin bash shell.
    cd mpich
    ./autogen.sh
    exit

(d) Execute winconfigure.wsf

(e) Open Developer Studio

    open mpich\mpich.sln
    build the ch3sockDebug mpich solution
    build the ch3sockDebug mpichs project
    build the ch3sockRelease mpich solution
    build the ch3sockRelease mpichs project
    build the Debug mpich solution
    build the Release mpich solution
    build the fortDebug mpich solution
    build the fortRelease mpich solution
    build the gfortDebug mpich solution
    build the gfortRelease mpich solution
    build the sfortDebug mpich solution
    build the sfortRelease mpich solution

(f) Open a command prompt

    cd to mpich\maint
    execute "makegcclibs.bat"

(g) Open another Developer Studio instance

    open mpich\examples\examples.sln
    build the Release target of the cpi project

(h) Return to Developer Studio with the mpich solution

    set the version numbers in the Installer project
    build the Installer mpich solution

(i) Test and distribute mpich\maint\ReleaseMSI\mpich.msi

    mpich.msi can be renamed, eg mpich-1.1.msi

(j) To install the launcher:

    Copy smpd.exe to a local directory on all the nodes.
    Log on to each node as an administrator and execute "smpd.exe -install"

(k) Compile and run an MPI application:

    Compile an mpi application.  Use mpi.h from mpich\src\include\win32
    and mpi.lib in mpich\lib
    
    Place your executable along with the mpich dlls somewhere accessable
    to all the machines.
    
    Execute a job by running something like: mpiexec -n 3 myapp.exe

-------------------------------------------------------------------------

12. Multiple Fortran compiler support
=====================================

If the C compiler that is used to build MPICH libraries supports both
multiple weak symbols and multiple aliases of common symbols, the
Fortran 77 binding can support multiple Fortran compilers. The
multiple weak symbols support allow MPICH to provide different name
mangling scheme (of subroutine names) required by differen Fortran
compilers. The multiple aliases of common symbols support enables
MPICH to equal different common block symbols of the MPI Fortran
constant, e.g. MPI_IN_PLACE, MPI_STATUS_IGNORE. So they are understood
by different Fortran compilers.

Since the support of multiple aliases of common symbols is
new/experimental, users can disable the feature by using configure
option --disable-multi-aliases if it causes any undesirable effect,
e.g. linker warnings of different sizes of common symbols, MPIFCMB*
(the warning should be harmless).

We have only tested this support on a limited set of
platforms/compilers.  On linux, if the C compiler that builds MPICH
is either gcc or icc, the above support will be enabled by configure.
At the time of this writing, pgcc does not seem to have this multiple
aliases of common symbols, so configure will detect the deficiency and
disable the feature automatically.  The tested Fortran compiler
includes GNU Forran compilers(gfortan, g77), Intel Fortran
compiler(ifort), Portland Group Fortran compilers(pgf77, pgf90),
Absoft Fortran compilers (af77, af90), and IBM XL fortran
compiler(xlf).  What this mean is that if mpich is built by
gcc/gfortran, the resulting mpich library can be used to link a
Fortran program compiled/linked by another fortran compiler, say
pgf77, say through mpif77 -f77=pgf77.  As long as the Fortran program
is linked without any errors by one of these compilers, the program
shall be running fine.
