MPICH Release 3.3.2

MPICH is a high-performance and widely portable implementation of the

MPI-3.1 standard from the Argonne National Laboratory.  This release

has all MPI 3.1 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.mpich.org, 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.  Developer Builds

10. Multiple Fortran compiler support

11. ABI Compatibility

12. Capability Sets

13. Threads

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

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-3.3.2.tar.gz

    - REQUIRED: A C compiler (C99 support is required. See

      https://wiki.mpich.org/mpich/index.php/Shifting_toward_C99)

    - 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 compiler, if Fortran applications are to be

      used (gfortran, ifort, etc.). If you do not require support for

      Fortran applications, you can disable this support using

      --disable-fortran (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-3.3.2.tar.gz

      cd mpich-3.3.2

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

      gunzip mpich-3.3.2.tar.gz

      tar xf mpich-3.3.2.tar

      cd mpich-3.3.2

(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 compiler found. If you don't need to build any

        Fortran programs, you can disable Fortran support using

        --disable-fortran. 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-3.3.2/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 discuss@mpich.org mailing list archive

(https://lists.mpich.org/mailman/listinfo/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

discuss@mpich.org. You need to subscribe to this list

(https://lists.mpich.org/mailman/listinfo/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-3.3.2/c.txt (generated in step 1(d) above)

    mpich-3.3.2/m.txt (generated in step 1(e) above)

    mpich-3.3.2/mi.txt (generated in step 1(f) above)

    mpich-3.3.2/config.log (generated in step 1(d) above)

    mpich-3.3.2/src/openpa/config.log (generated in step 1(d) above)

    mpich-3.3.2/src/mpl/config.log (generated in step 1(d) above)

    mpich-3.3.2/src/pm/hydra/config.log (generated in step 1(d) above)

    mpich-3.3.2/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, you can report it on our Github

page (https://github.com/pmodels/mpich/issues).

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

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, and MPICHLIB_FCFLAGS (abbreviated as

MPICHLIB_xFLAGS): Setting these flags would result in the MPICH

library being compiled with these flags.  However, these flags will

*not* be used by mpicc and friends.

(c) MPICH_MPICC_CFLAGS, MPICH_MPICC_CPPFLAGS, MPICH_MPICC_LDFLAGS,

MPICH_MPICC_LIBS, and so on for MPICXX, MPIF77 and MPIFORT

(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_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".

For performance testing, we recommend the following flags:

  ./configure --enable-fast=O3,ndebug --disable-error-checking --without-timing \

              --without-mpit-pvars

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.

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

4. Alternate Channels and Devices

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

The communication mechanisms in MPICH are called "devices". MPICH

supports ch3 (default) and ch4 (experimental), as well as many

third-party devices that are released and maintained by other

institutes.

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

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

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.

mxm network module

``````````````````

The mxm netmod provides support for Mellanox InfiniBand adapters.  It

can be built with the following configure option:

  --with-device=ch3:nemesis:mxm

If your MXM library is installed in a non-standard location, you might

need to help configure find it using the following configure option

(assuming the libraries are present in /path/to/mxm/lib and the

include headers are present in /path/to/mxm/include):

  --with-mxm=/path/to/mxm

(or)

  --with-mxm-lib=/path/to/mxm/lib

  --with-mxm-include=/path/to/mxm/include

By default, the mxm library throws warnings when the system does not

enable certain features that might hurt performance.  These are

important warnings that might cause performance degradation on your

system.  But you might need root privileges to fix some of them.  If

you would like to disable such warnings, you can set the MXM log level

to "error" instead of the default "warn" by using:

  MXM_LOG_LEVEL=error

  export MXM_LOG_LEVEL

portals4 network module

```````````````````````

The portals4 netmod provides support for the Portals 4 network

programming interface. To enable, configure with the following option:

  --with-device=ch3:nemesis:portals4

If the Portals 4 include files and libraries are not in the normal

search paths, you can specify them with the following options:

  --with-portals4-include= and --with-portals4-lib=

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

the following option:

  --with-portals4=

If the Portals 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

environment. 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.

Currently, use of MPI_ANY_SOURCE and MPI dynamic processes are unsupported

with the portals4 netmod.

ofi network module

```````````````````

The ofi netmod provides support for the OFI network programming interface.

To enable, configure with the following option:

  --with-device=ch3:nemesis:ofi

If the OFI include files and libraries are not in the normal search paths,

you can specify them with the following options:

  --with-ofi-include= and --with-ofi-lib=

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

the following option:

  --with-ofi=

If the OFI 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

environment. 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.

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

ch4 device

**********

The ch4 device contains different network and shared memory modules

for communication. We currently support the ofi and ucx network

modules, and posix shared memory module.

ofi network module

```````````````````

The ofi netmod provides support for the OFI network programming interface.

To enable, configure with the following option:

  --with-device=ch4:ofi

If the OFI include files and libraries are not in the normal search paths,

you can specify them with the following options:

  --with-libfabric-include= and --with-libfabric-lib=

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

the following option:

  --with-libfabric=

ucx network module

``````````````````

The ucx netmod provides support for the Unified Communication X

library. It can be built with the following configure option:

  --with-device=ch4:ucx

If the UCX include files and libraries are not in the normal search paths,

you can specify them with the following options:

  --with-ucx-include= and --with-ucx-lib=

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

the following option:

  --with-ucx=

By default, the UCX library throws warnings when the system does not

enable certain features that might hurt performance.  These are

important warnings that might cause performance degradation on your

system.  But you might need root privileges to fix some of them.  If

you would like to disable such warnings, you can set the UCX log level

to "error" instead of the default "warn" by using:

  UCX_LOG_LEVEL=error

  export UCX_LOG_LEVEL

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

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

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

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

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. Developer Builds

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

For MPICH developers who want to directly work on the primary version

control system, 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

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

10. 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 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 compilers

include GNU Fortran compilers (gfortan), Intel Fortran compiler

(ifort), Portland Group Fortran compilers (pgfortran), Absoft Fortran

compilers (af90), and IBM XL fortran compiler (xlf).  What this means

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 pgf90, say through mpifort -fc=pgf90.  As long

as the Fortran program is linked without any errors by one of these

compilers, the program shall be running fine.

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

11. ABI Compatibility

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

The MPICH ABI compatibility initiative was announced at SC 2014

(http://www.mpich.org/abi).  As a part of this initiative, Argonne,

Intel, IBM and Cray have committed to maintaining ABI compatibility

with each other.

As a first step in this initiative, starting with version 3.1, MPICH

is binary (ABI) compatible with Intel MPI 5.0.  This means you can

build your program with one MPI implementation and run with the other.

Specifically, binary-only applications that were built and distributed

with one of these MPI implementations can now be executed with the

other MPI implementation.

Some setup is required to achieve this.  Suppose you have MPICH

installed in /path/to/mpich and Intel MPI installed in /path/to/impi.

You can run your application with mpich using:

   % export LD_LIBRARY_PATH=/path/to/mpich/lib:$LD_LIBRARY_PATH

   % mpiexec -np 100 ./foo

or using Intel MPI using:

   % export LD_LIBRARY_PATH=/path/to/impi/lib:$LD_LIBRARY_PATH

   % mpiexec -np 100 ./foo

This works irrespective of which MPI implementation your application

was compiled with, as long as you use one of the MPI implementations

in the ABI compatibility initiative.

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

12. Capability Sets

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

The CH4 device contains a feature called "capability sets" to simplify

configuration of MPICH on systems using the OFI netmod. This feature

configures MPICH to use a predetermined set of OFI features based on the

provider being used. Capability sets can be configured at compile time or

runtime. Compile time configuration provides better performance by

reducing unnecessary code branches, but at the cost of flexibility.

To configure at compile time, the device string should be amended to include

the OFI provider with the following option:

    --with-device=ch4:ofi:sockets

This will setup the OFI netmod to use the optimal configuration for the

sockets provider, and will set various compile time constants. These settings

cannot be changed at runtime.

If runtime configuration is needed, continue to use the device string as before

(without the OFI provider extension) and set various environment variables to

achieve a similar configuration. To select the desired provider:

    % export MPIR_CVAR_OFI_USE_PROVIDER=sockets

This will select the OFI provider and the associated MPICH capability set. To

change the preset configuration, there exists an extended set of environment

variables. As an example, the immediate data fields can be disabled by using

the environment variable:

    % export MPIR_CVAR_OFI_ENABLE_DATA=0

A full list of capability set configuration variables can be found in the

environment variables README.envvar.

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

13. Threads

===========

MPICH supports multiple threading packages.  The default is posix

threads (pthreads), but solaris threads, windows threads and argobots

are also supported.

To configure mpich to work with argobots threads, use the following

configure options:

    --with-thread-package=argobots \

        CFLAGS="-I<path_to_argobots/include>" \