# Open MPI
The Open MPI Project is an open source Message Passing Interface (MPI)
implementation that is developed and maintained by a consortium of
academic, research, and industry partners. Open MPI is therefore able
to combine the expertise, technologies, and resources from all across
the High Performance Computing community in order to build the best
MPI library available. Open MPI offers advantages for system and
software vendors, application developers and computer science
researchers.
See [the MPI Forum web site](https://mpi-forum.org/) for information
about the MPI API specification.
## Quick start
In many cases, Open MPI can be built and installed by simply
indicating the installation directory on the command line:
```
$ tar xf openmpi-<version>.tar.bz2
$ cd openmpi-<version>
$ ./configure --prefix=<path> |& tee config.out
...lots of output...
$ make -j 8 |& tee make.out
...lots of output...
$ make install |& tee install.out
...lots of output...
```
Note that there are many, many configuration options to the
`./configure` step. Some of them may be needed for your particular
environmnet; see below for desciptions of the options available.
If your installation prefix path is not writable by a regular user,
you may need to use sudo or su to run the `make install` step. For
example:
```
$ sudo make install |& tee install.out
[sudo] password for jsquyres: <enter your password here>
...lots of output...
```
Finally, note that VPATH builds are fully supported. For example:
```
$ tar xf openmpi-<version>.tar.bz2
$ cd openmpi-<version>
$ mkdir build
$ cd build
$ ../configure --prefix=<path> |& tee config.out
...etc.
```
## Table of contents
The rest of this file contains:
* [General release notes about Open MPI](#general-notes)
* [Platform-specific notes](#platform-notes)
* [Compiler-specific notes](#compiler-notes)
* [Run-time support notes](#general-run-time-support-notes)
* [MPI functionality and features](#mpi-functionality-and-features)
* [OpenSHMEM functionality and
features](#openshmem-functionality-and-features)
* [MPI collectives](#mpi-collectives)
* [OpenSHMEM collectives](#openshmem-collectives)
* [Network support](#network-support)
* [Open MPI extensions](#open-mpi-extensions)
* [Detailed information on building Open MPI](#building-open-mpi)
* [Installation options](#installation-options)
* [Networking support and options](#networking-support--options)
* [Run-time system support and options](#run-time-system-support)
* [Miscellaneous support
libraries](#miscellaneous-support-libraries)
* [MPI functionality options](#mpi-functionality)
* [OpenSHMEM functionality options](#openshmem-functionality)
* [Miscellaneous functionality
options](#miscellaneous-functionality)
* [Open MPI version and library numbering
policies](#open-mpi-version-numbers-and-binary-compatibility)
* [Backwards compatibility polices](#backwards-compatibility)
* [Software version numbering](#software-version-number)
* [Shared library version numbering](#shared-library-version-number)
* [Information on how to both query and validate your Open MPI
installation](#checking-your-open-mpi-installation)
* [Description of Open MPI extensions](#open-mpi-api-extensions)
* [Compiling the extensions](#compiling-the-extensions)
* [Using the extensions](#using-the-extensions)
* [Examples showing how to compile Open MPI applications](#compiling-open-mpi-applications)
* [Examples showing how to run Open MPI applications](#running-open-mpi-applications)
* [Summary information on the various plugin
frameworks](#the-modular-component-architecture-mca)
* [MPI layer frameworks](#mpi-layer-frameworks)
* [OpenSHMEM component frameworks](#openshmem-component-frameworks)
* [Run-time environment
frameworks](#back-end-run-time-environment-rte-component-frameworks)
* [Miscellaneous frameworks](#miscellaneous-frameworks)
* [Other notes about frameworks](#framework-notes)
* [How to get more help](#questions--problems)
Also, note that much, much more information is also available [in the
Open MPI FAQ](https://www.open-mpi.org/faq/).
## General notes
The following abbreviated list of release notes applies to this code
base as of this writing (April 2020):
* Open MPI now includes two public software layers: MPI and OpenSHMEM.
Throughout this document, references to Open MPI implicitly include
both of these layers. When distinction between these two layers is
necessary, we will reference them as the "MPI" and "OpenSHMEM"
layers respectively.
* OpenSHMEM is a collaborative effort between academia, industry, and
the U.S. Government to create a specification for a standardized API
for parallel programming in the Partitioned Global Address Space
(PGAS). For more information about the OpenSHMEM project, including
access to the current OpenSHMEM specification, please visit
http://openshmem.org/.
This OpenSHMEM implementation will only work in Linux environments
with a restricted set of supported networks.
* Open MPI includes support for a wide variety of supplemental
hardware and software package. When configuring Open MPI, you may
need to supply additional flags to the `configure` script in order
to tell Open MPI where the header files, libraries, and any other
required files are located. As such, running `configure` by itself
may not include support for all the devices (etc.) that you expect,
especially if their support headers / libraries are installed in
non-standard locations. Network interconnects are an easy example
to discuss -- Libfabric and OpenFabrics networks, for example, both
have supplemental headers and libraries that must be found before
Open MPI can build support for them. You must specify where these
files are with the appropriate options to configure. See the
listing of configure command-line switches, below, for more details.
* The majority of Open MPI's documentation is here in this file, the
included man pages, and on [the web site
FAQ](https://www.open-mpi.org/).
* Note that Open MPI documentation uses the word "component"
frequently; the word "plugin" is probably more familiar to most
users. As such, end users can probably completely substitute the
word "plugin" wherever you see "component" in our documentation.
For what it's worth, we use the word "component" for historical
reasons, mainly because it is part of our acronyms and internal API
function calls.
* The run-time systems that are currently supported are:
* rsh / ssh
* PBS Pro, Torque
* Platform LSF (tested with v9.1.1 and later)
* SLURM
* Cray XE, XC, and XK
* Oracle Grid Engine (OGE) 6.1, 6.2 and open source Grid Engine
* Systems that have been tested are:
* Linux (various flavors/distros), 64 bit (x86, ppc, aarch64),
with gcc (>=4.8.x+), clang (>=3.6.0), Absoft (fortran), Intel,
and Portland (*)
* macOS (10.14-10.15), 64 bit (x86_64) with XCode compilers
(*) Be sure to read the Compiler Notes, below.
* Other systems have been lightly (but not fully) tested:
* Linux (various flavors/distros), 32 bit, with gcc
* Cygwin 32 & 64 bit with gcc
* ARMv6, ARMv7
* Other 64 bit platforms.
* OpenBSD. Requires configure options `--enable-mca-no-build=patcher`
and `--disable-dlopen` with this release.
* Problems have been reported when building Open MPI on FreeBSD 11.1
using the clang-4.0 system compiler. A workaround is to build
Open MPI using the GNU compiler.
* Open MPI has taken some steps towards [Reproducible
Builds](https://reproducible-builds.org/). Specifically, Open MPI's
`configure` and `make` process, by default, records the build date
and some system-specific information such as the hostname where Open
MPI was built and the username who built it. If you desire a
Reproducible Build, set the `$SOURCE_DATE_EPOCH`, `$USER` and
`$HOSTNAME` environment variables before invoking `configure` and
`make`, and Open MPI will use those values instead of invoking
`whoami` and/or `hostname`, respectively. See
https://reproducible-builds.org/docs/source-date-epoch/ for
information on the expected format and content of the
`$SOURCE_DATE_EPOCH` variable.
### Platform Notes
- N/A
### Compiler Notes
* Open MPI requires a C99-capable compiler to build.
* On platforms other than x86-64, ARM, and PPC, Open MPI requires a
compiler that either supports C11 atomics or the GCC `__atomic`
atomics (e.g., GCC >= v4.7.2).
* Mixing compilers from different vendors when building Open MPI
(e.g., using the C/C++ compiler from one vendor and the Fortran
compiler from a different vendor) has been successfully employed by
some Open MPI users (discussed on the Open MPI user's mailing list),
but such configurations are not tested and not documented. For
example, such configurations may require additional compiler /
linker flags to make Open MPI build properly.
A not-uncommon case for this is when building on MacOS with the
system-default GCC compiler (i.e., `/usr/bin/gcc`), but a 3rd party
gfortran (e.g., provided by Homebrew, in `/usr/local/bin/gfortran`).
Since these compilers are provided by different organizations, they
have different default search paths. For example, if Homebrew has
also installed a local copy of Libevent (a 3rd party package that
Open MPI requires), the MacOS-default `gcc` linker will find it
without any additional command line flags, but the Homebrew-provided
gfortran linker will not. In this case, it may be necessary to
provide the following on the configure command line:
```
$ ./configure FCFLAGS=-L/usr/local/lib ...
```
This `-L` flag will then be passed to the Fortran linker when
creating Open MPI's Fortran libraries, and it will therefore be able
to find the installed Libevent.
* In general, the latest versions of compilers of a given vendor's
series have the least bugs. We have seen cases where Vendor XYZ's
compiler version A.B fails to compile Open MPI, but version A.C
(where C>B) works just fine. If you run into a compile failure, you
might want to double check that you have the latest bug fixes and
patches for your compiler.
* Users have reported issues with older versions of the Fortran PGI
compiler suite when using Open MPI's (non-default) `--enable-debug`
configure option. Per the above advice of using the most recent
version of a compiler series, the Open MPI team recommends using the
latest version of the PGI suite, and/or not using the `--enable-debug`
configure option. If it helps, here's what we have found with some
(not comprehensive) testing of various versions of the PGI compiler
suite:
* pgi-8 : NO known good version with `--enable-debug`
* pgi-9 : 9.0-4 known GOOD
* pgi-10: 10.0-0 known GOOD
* pgi-11: NO known good version with `--enable-debug`
* pgi-12: 12.10 known BAD with `-m32`, but known GOOD without `-m32`
(and 12.8 and 12.9 both known BAD with `--enable-debug`)
* pgi-13: 13.9 known BAD with `-m32`, 13.10 known GOOD without `-m32`
* pgi-15: 15.10 known BAD with `-m32`
* Similarly, there is a known Fortran PGI compiler issue with long
source directory path names that was resolved in 9.0-4 (9.0-3 is
known to be broken in this regard).
* Open MPI does not support the PGI compiler suite on OS X or MacOS.
See issues below for more details:
* https://github.com/open-mpi/ompi/issues/2604
* https://github.com/open-mpi/ompi/issues/2605
* OpenSHMEM Fortran bindings do not support the "no underscore"
Fortran symbol convention. IBM's `xlf` compilers build in that mode
by default. As such, IBM's `xlf` compilers cannot build/link the
OpenSHMEM Fortran bindings by default. A workaround is to pass
`FC="xlf -qextname"` at configure time to force a trailing
underscore. See [this
issue](https://github.com/open-mpi/ompi/issues/3612) for more
details.
* MPI applications that use the mpi_f08 module on PowerPC platforms
(tested ppc64le) will likely experience runtime failures if:
* they are using a GNU linker (ld) version after v2.25.1 and before v2.28,
*and*
* they compiled with PGI (tested 17.5) or XL (tested v15.1.5) compilers.
This was noticed on Ubuntu 16.04 which uses the 2.26.1 version of
`ld` by default. However, this issue impacts any OS using a version
of `ld` noted above. This GNU linker regression will be fixed in
version 2.28. [Here is a link to the GNU bug on this
issue](https://sourceware.org/bugzilla/show_bug.cgi?id=21306). The
XL compiler will include a fix for this issue in a future release.
* On NetBSD-6 (at least AMD64 and i386), and possibly on OpenBSD,
Libtool misidentifies properties of f95/g95, leading to obscure
compile-time failures if used to build Open MPI. You can work
around this issue by ensuring that libtool will not use f95/g95
(e.g., by specifying `FC=<some_other_compiler>`, or otherwise ensuring
a different Fortran compiler will be found earlier in the path than
`f95`/`g95`), or by disabling the Fortran MPI bindings with
`--disable-mpi-fortran`.
* On OpenBSD/i386, if you configure with
`--enable-mca-no-build=patcher`, you will also need to add
`--disable-dlopen`. Otherwise, odd crashes can occur
nondeterministically.
* Absoft 11.5.2 plus a service pack from September 2012 (which Absoft
says is available upon request), or a version later than 11.5.2
(e.g., 11.5.3), is required to compile the Fortran `mpi_f08`
module.
* Open MPI does not support the Sparc v8 CPU target. However,
as of Solaris Studio 12.1, and later compilers, one should not
specify `-xarch=v8plus` or `-xarch=v9`. The use of the options
`-m32` and `-m64` for producing 32 and 64 bit targets, respectively,
are now preferred by the Solaris Studio compilers. GCC may
require either `-m32` or `-mcpu=v9 -m32`, depending on GCC version.
* If one tries to build OMPI on Ubuntu with Solaris Studio using the C++
compiler and the `-m32` option, you might see a warning:
```
CC: Warning: failed to detect system linker version, falling back to custom linker usage
```
And the build will fail. One can overcome this error by either
setting `LD_LIBRARY_PATH` to the location of the 32 bit libraries
(most likely /lib32), or giving `LDFLAGS="-L/lib32 -R/lib32"` to the
`configure` command. Officially, Solaris Studio is not supported on
Ubuntu Linux distributions, so additional problems might be
incurred.
* Open MPI does not support the `gccfss` compiler (GCC For SPARC
Systems; a now-defunct compiler project from Sun).
* At least some versions of the Intel 8.1 compiler seg fault while
compiling certain Open MPI source code files. As such, it is not
supported.
* It has been reported that the Intel 9.1 and 10.0 compilers fail to
compile Open MPI on IA64 platforms. As of 12 Sep 2012, there is
very little (if any) testing performed on IA64 platforms (with any
compiler). Support is "best effort" for these platforms, but it is
doubtful that any effort will be expended to fix the Intel 9.1 /
10.0 compiler issuers on this platform.
* Early versions of the Intel 12.1 Linux compiler suite on x86_64 seem
to have a bug that prevents Open MPI from working. Symptoms
including immediate segv of the wrapper compilers (e.g., `mpicc`) and
MPI applications. As of 1 Feb 2012, if you upgrade to the latest
version of the Intel 12.1 Linux compiler suite, the problem will go
away.
* The Portland Group compilers prior to version 7.0 require the
`-Msignextend` compiler flag to extend the sign bit when converting
from a shorter to longer integer. This is is different than other
compilers (such as GNU). When compiling Open MPI with the Portland
compiler suite, the following flags should be passed to Open MPI's
`configure` script:
```
shell$ ./configure CFLAGS=-Msignextend CXXFLAGS=-Msignextend \
--with-wrapper-cflags=-Msignextend \
--with-wrapper-cxxflags=-Msignextend ...
```
This will both compile Open MPI with the proper compile flags and
also automatically add "-Msignextend" when the C and C++ MPI wrapper
compilers are used to compile user MPI applications.
* It has been reported that Pathscale 5.0.5 and 6.0.527 compilers
give an internal compiler error when trying to build Open MPI.
* As of July 2017, the Pathscale compiler suite apparently has no
further commercial support, and it does not look like there will be
further releases. Any issues discovered regarding building /
running Open MPI with the Pathscale compiler suite therefore may not
be able to be resolved.
* Using the Absoft compiler to build the MPI Fortran bindings on Suse
9.3 is known to fail due to a Libtool compatibility issue.
* MPI Fortran API support has been completely overhauled since the
Open MPI v1.5/v1.6 series.
There is now only a single Fortran MPI wrapper compiler and a
single Fortran OpenSHMEM wrapper compiler: `mpifort` and `oshfort`,
respectively. `mpif77` and `mpif90` still exist, but they are
symbolic links to `mpifort`.
Similarly, Open MPI's `configure` script only recognizes the `FC`
and `FCFLAGS` environment variables (to specify the Fortran
compiler and compiler flags, respectively). The `F77` and `FFLAGS`
environment variables are ***IGNORED***.
As a direct result, it is ***STRONGLY*** recommended that you
specify a Fortran compiler that uses file suffixes to determine
Fortran code layout (e.g., free form vs. fixed). For example, with
some versions of the IBM XLF compiler, it is preferable to use
`FC=xlf` instead of `FC=xlf90`, because `xlf` will automatically
determine the difference between free form and fixed Fortran source
code.
However, many Fortran compilers allow specifying additional
command-line arguments to indicate which Fortran dialect to use.
For example, if `FC=xlf90`, you may need to use `mpifort --qfixed ...`
to compile fixed format Fortran source files.
You can use either `ompi_info` or `oshmem_info` to see with which
Fortran compiler Open MPI was configured and compiled.
There are up to three sets of Fortran MPI bindings that may be
provided (depending on your Fortran compiler):
1. `mpif.h`: This is the first MPI Fortran interface that was
defined in MPI-1. It is a file that is included in Fortran
source code. Open MPI's `mpif.h` does not declare any MPI
subroutines; they are all implicit.
1. `mpi` module: The `mpi` module file was added in MPI-2. It
provides strong compile-time parameter type checking for MPI
subroutines.
1. `mpi_f08` module: The `mpi_f08` module was added in MPI-3. It
provides many advantages over the `mpif.h` file and `mpi` module.
For example, MPI handles have distinct types (vs. all being
integers). See the MPI-3 document for more details.
***NOTE:*** The `mpi_f08` module is ***STRONGLY*** recommended for
all new MPI Fortran subroutines and applications. Note that the
`mpi_f08` module can be used in conjunction with the other two
Fortran MPI bindings in the same application (only one binding can
be used per subroutine/function, however). Full interoperability
between `mpif.h`/`mpi` module and `mpi_f08` module MPI handle types
is provided, allowing `mpi_f08` to be used in new subroutines in
legacy MPI applications.
Per the OpenSHMEM specification, there is only one Fortran OpenSHMEM
binding provided:
* `shmem.fh`: All Fortran OpenSHMEM programs should include
`shmem.f`, and Fortran OpenSHMEM programs that use constants
defined by OpenSHMEM ***MUST*** include `shmem.fh`.
The following notes apply to the above-listed Fortran bindings:
* All Fortran compilers support the `mpif.h`/`shmem.fh`-based
bindings, with one exception: the `MPI_SIZEOF` interfaces will
only be present when Open MPI is built with a Fortran compiler
that supports the `INTERFACE` keyword and `ISO_FORTRAN_ENV`. Most
notably, this excludes the GNU Fortran compiler suite before
version 4.9.
* The level of support provided by the `mpi` module is based on your
Fortran compiler.
If Open MPI is built with a non-GNU Fortran compiler, or if Open
MPI is built with the GNU Fortran compiler >= v4.9, all MPI
subroutines will be prototyped in the `mpi` module. All calls to
MPI subroutines will therefore have their parameter types checked
at compile time.
If Open MPI is built with an old `gfortran` (i.e., < v4.9), a
limited `mpi` module will be built. Due to the limitations of
these compilers, and per guidance from the MPI-3 specification,
all MPI subroutines with "choice" buffers are specifically *not*
included in the `mpi` module, and their parameters will not be
checked at compile time. Specifically, all MPI subroutines with
no "choice" buffers are prototyped and will receive strong
parameter type checking at run-time (e.g., `MPI_INIT`,
`MPI_COMM_RANK`, etc.).
Similar to the `mpif.h` interface, `MPI_SIZEOF` is only supported
on Fortran compilers that support `INTERFACE` and
`ISO_FORTRAN_ENV`.
* The `mpi_f08` module has been tested with the Intel Fortran
compiler and gfortran >= 4.9. Other modern Fortran compilers
likely also work.
Many older Fortran compilers do not provide enough modern Fortran
features to support the `mpi_f08` module. For example, `gfortran`
< v4.9 does provide enough support for the `mpi_f08` module.
You can examine the output of the following command to see all
the Fortran features that are/are not enabled in your Open MPI
installation:
```
shell$ ompi_info | grep -i fort
```
### General Run-Time Support Notes
* The Open MPI installation must be in your `PATH` on all nodes (and
potentially `LD_LIBRARY_PATH` or `DYLD_LIBRARY_PATH`, if
`libmpi`/`libshmem` is a shared library), unless using the
`--prefix` or `--enable-mpirun-prefix-by-default` functionality (see
below).
* Open MPI's run-time behavior can be customized via Modular Component
Architecture (MCA) parameters (see below for more information on how
to get/set MCA parameter values). Some MCA parameters can be set in
a way that renders Open MPI inoperable (see notes about MCA
parameters later in this file). In particular, some parameters have
required options that must be included.
* If specified, the `btl` parameter must include the `self`
component, or Open MPI will not be able to deliver messages to the
same rank as the sender. For example: `mpirun --mca btl tcp,self
...`
* If specified, the `btl_tcp_if_exclude` parameter must include the
loopback device (`lo` on many Linux platforms), or Open MPI will
not be able to route MPI messages using the TCP BTL. For example:
`mpirun --mca btl_tcp_if_exclude lo,eth1 ...`
* Running on nodes with different endian and/or different datatype
sizes within a single parallel job is supported in this release.
However, Open MPI does not resize data when datatypes differ in size
(for example, sending a 4 byte `MPI_DOUBLE` and receiving an 8 byte
`MPI_DOUBLE` will fail).
### MPI Functionality and Features
* All MPI-3.1 functionality is supported.
* Note that starting with Open MPI v4.0.0, prototypes for several
legacy MPI-1 symbols that were deleted in the MPI-3.0 specification
(which was published in 2012) are no longer available by default in
`mpi.h`. Specifically, several MPI-1 symbols were deprecated in the
1996 publishing of the MPI-2.0 specification. These deprecated
symbols were eventually removed from the MPI-3.0 specification in
2012.
The symbols that now no longer appear by default in Open MPI's
`mpi.h` are:
* `MPI_Address` (replaced by `MPI_Get_address`)
* `MPI_Errhandler_create` (replaced by `MPI_Comm_create_errhandler`)
* `MPI_Errhandler_get` (replaced by `MPI_Comm_get_errhandler`)
* `MPI_Errhandler_set` (replaced by `MPI_Comm_set_errhandler`)
* `MPI_Type_extent` (replaced by `MPI_Type_get_extent`)
* `MPI_Type_hindexed` (replaced by `MPI_Type_create_hindexed`)
* `MPI_Type_hvector` (replaced by `MPI_Type_create_hvector`)
* `MPI_Type_lb` (replaced by `MPI_Type_get_extent`)
* `MPI_Type_struct` (replaced by `MPI_Type_create_struct`)
* `MPI_Type_ub` (replaced by `MPI_Type_get_extent`)
* `MPI_LB` (replaced by `MPI_Type_create_resized`)
* `MPI_UB` (replaced by `MPI_Type_create_resized`)
* `MPI_COMBINER_HINDEXED_INTEGER`
* `MPI_COMBINER_HVECTOR_INTEGER`
* `MPI_COMBINER_STRUCT_INTEGER`
* `MPI_Handler_function` (replaced by `MPI_Comm_errhandler_function`)
Although these symbols are no longer prototyped in `mpi.h`, they
are still present in the MPI library in Open MPI v4.0.x. This
enables legacy MPI applications to link and run successfully with
Open MPI v4.0.x, even though they will fail to compile.
***WARNING:*** Future releases of Open MPI beyond the v4.0.x series
may remove these symbols altogether.
***WARNING:*** The Open MPI team ***STRONGLY*** encourages all MPI
application developers to stop using these constructs that were
first deprecated over 20 years ago, and finally removed from the MPI
specification in MPI-3.0 (in 2012).
***WARNING:*** [The Open MPI
FAQ](https://www.open-mpi.org/faq/?category=mpi-removed) contains
examples of how to update legacy MPI applications using these
deleted symbols to use the "new" symbols.
All that being said, if you are unable to immediately update your
application to stop using these legacy MPI-1 symbols, you can
re-enable them in `mpi.h` by configuring Open MPI with the
`--enable-mpi1-compatibility` flag.
* Rank reordering support is available using the TreeMatch library. It
is activated for the graph and `dist_graph` communicator topologies.
* When using MPI deprecated functions, some compilers will emit
warnings. For example:
```
shell$ cat deprecated_example.c
#include <mpi.h>
void foo(void) {
MPI_Datatype type;
MPI_Type_struct(1, NULL, NULL, NULL, &type);
}
shell$ mpicc -c deprecated_example.c
deprecated_example.c: In function 'foo':
deprecated_example.c:4: warning: 'MPI_Type_struct' is deprecated (declared at /opt/openmpi/include/mpi.h:1522)
shell$
```
* `MPI_THREAD_MULTIPLE` is supported with some exceptions.
The following PMLs support `MPI_THREAD_MULTIPLE`:
1. `cm` (see list (1) of supported MTLs, below)
1. `ob1` (see list (2) of supported BTLs, below)
1. `ucx`
(1) The `cm` PML and the following MTLs support `MPI_THREAD_MULTIPLE`:
1. `ofi` (Libfabric)
1. `portals4`
(2) The `ob1` PML and the following BTLs support `MPI_THREAD_MULTIPLE`:
1. `self`
1. `sm`
1. `smcuda`
1. `tcp`
1. `ugni`
1. `usnic`
Currently, MPI File operations are not thread safe even if MPI is
initialized for `MPI_THREAD_MULTIPLE` support.
* `MPI_REAL16` and `MPI_COMPLEX32` are only supported on platforms
where a portable C datatype can be found that matches the Fortran
type `REAL*16`, both in size and bit representation.
* The "libompitrace" library is bundled in Open MPI and is installed
by default (it can be disabled via the `--disable-libompitrace`
flag). This library provides a simplistic tracing of select MPI
function calls via the MPI profiling interface. Linking it in to
your application via (e.g., via `-lompitrace`) will automatically
output to stderr when some MPI functions are invoked:
```
shell$ cd examples/
shell$ mpicc hello_c.c -o hello_c -lompitrace
shell$ mpirun -np 1 hello_c
MPI_INIT: argc 1
Hello, world, I am 0 of 1
MPI_BARRIER[0]: comm MPI_COMM_WORLD
MPI_FINALIZE[0]
shell$
```
Keep in mind that the output from the trace library is going to
`stderr`, so it may output in a slightly different order than the
`stdout` from your application.
This library is being offered as a "proof of concept" / convenience
from Open MPI. If there is interest, it is trivially easy to extend
it to printf for other MPI functions. Pull requests on github.com
would be greatly appreciated.
### OpenSHMEM Functionality and Features
All OpenSHMEM-1.3 functionality is supported.
### MPI Collectives
* The `cuda` coll component provides CUDA-aware support for the
reduction type collectives with GPU buffers. This component is only
compiled into the library when the library has been configured with
CUDA-aware support. It intercepts calls to the reduction
collectives, copies the data to staging buffers if GPU buffers, then
calls underlying collectives to do the work.
### OpenSHMEM Collectives
* The `fca` scoll component: the Mellanox Fabric Collective
Accelerator (FCA) is a solution for offloading collective operations
from the MPI process onto Mellanox QDR InfiniBand switch CPUs and
HCAs.
* The `basic` scoll component: Reference implementation of all
OpenSHMEM collective operations.
### Network Support
* There are several main MPI network models available: `ob1`, `cm`,
and `ucx`. `ob1` uses BTL ("Byte Transfer Layer")
components for each supported network. `cm` uses MTL ("Matching
Transport Layer") components for each supported network. `ucx` uses
the OpenUCX transport.
* `ob1` supports a variety of networks that can be used in
combination with each other:
* OpenFabrics: InfiniBand, iWARP, and RoCE
* Loopback (send-to-self)
* Shared memory
* TCP
* SMCUDA
* Cisco usNIC
* uGNI (Cray Gemini, Aries)
* shared memory (XPMEM, Linux CMA, Linux KNEM, and
copy-in/copy-out shared memory)
* `cm` supports a smaller number of networks (and they cannot be
used together), but may provide better overall MPI performance:
* Intel Omni-Path PSM2 (version 11.2.173 or later)
* Intel True Scale PSM (QLogic InfiniPath)
* OpenFabrics Interfaces ("libfabric" tag matching)
* Portals 4
* UCX is the [Unified Communication X (UCX) communication
library](https://www.openucx.org/). This is an open-source
project developed in collaboration between industry, laboratories,
and academia to create an open-source production grade
communication framework for data centric and high-performance
applications. The UCX library can be downloaded from repositories
(e.g., Fedora/RedHat yum repositories). The UCX library is also
part of Mellanox OFED and Mellanox HPC-X binary distributions.
UCX currently supports:
* OpenFabrics Verbs (including InfiniBand and RoCE)
* Cray's uGNI
* TCP
* Shared memory
* NVIDIA CUDA drivers
While users can manually select any of the above transports at run
time, Open MPI will select a default transport as follows:
1. If InfiniBand devices are available, use the UCX PML.
1. If PSM, PSM2, or other tag-matching-supporting Libfabric
transport devices are available (e.g., Cray uGNI), use the `cm`
PML and a single appropriate corresponding `mtl` module.
1. Otherwise, use the `ob1` PML and one or more appropriate `btl`
modules.
Users can override Open MPI's default selection algorithms and force
the use of a specific transport if desired by setting the `pml` MCA
parameter (and potentially the `btl` and/or `mtl` MCA parameters) at
run-time:
```
shell$ mpirun --mca pml ob1 --mca btl [comma-delimted-BTLs] ...
or
shell$ mpirun --mca pml cm --mca mtl [MTL] ...
or
shell$ mpirun --mca pml ucx ...
```
There is a known issue when using UCX with very old Mellanox
Infiniband HCAs, in particular HCAs preceding the introduction of
the ConnectX product line, which can result in Open MPI crashing in
MPI_Finalize. This issue is addressed by UCX release 1.9.0 and
newer.
* The main OpenSHMEM network model is `ucx`; it interfaces directly
with UCX.
* In prior versions of Open MPI, InfiniBand and RoCE support was
provided through the `openib` BTL and `ob1` PML plugins. Starting
with Open MPI 4.0.0, InfiniBand support through the `openib` plugin
is both deprecated and superseded by the `ucx` PML component. The
`openib` BTL was removed in Open MPI v5.0.0.
While the `openib` BTL depended on `libibverbs`, the UCX PML depends
on the UCX library.
Once installed, Open MPI can be built with UCX support by adding
`--with-ucx` to the Open MPI configure command. Once Open MPI is
configured to use UCX, the runtime will automatically select the
`ucx` PML if one of the supported networks is detected (e.g.,
InfiniBand). It's possible to force using UCX in the `mpirun` or
`oshrun` command lines by specifying any or all of the following mca
parameters: `--mca pml ucx` for MPI point-to-point operations,
`--mca spml ucx` for OpenSHMEM support, and `--mca osc ucx` for MPI
RMA (one-sided) operations.
* The `usnic` BTL is support for Cisco's usNIC device ("userspace NIC")
on Cisco UCS servers with the Virtualized Interface Card (VIC).
Although the usNIC is accessed via the OpenFabrics Libfabric API
stack, this BTL is specific to Cisco usNIC devices.
* uGNI is a Cray library for communicating over the Gemini and Aries
interconnects.
* The OpenFabrics Enterprise Distribution (OFED) software package v1.0
will not work properly with Open MPI v1.2 (and later) due to how its
Mellanox InfiniBand plugin driver is created. The problem is fixed
with OFED v1.1 (and later).
* The use of `fork()` with Libiverbs-based networks (i.e., the UCX
PML) is only partially supported, and only on Linux kernels >=
v2.6.15 with `libibverbs` v1.1 or later (first released as part of
OFED v1.2), per restrictions imposed by the OFED network stack.
* Linux `knem` support is used when the `sm` (shared memory) BTL is
compiled with knem support (see the `--with-knem` configure option)
and the `knem` Linux module is loaded in the running kernel. If the
`knem` Linux kernel module is not loaded, the `knem` support is (by
default) silently deactivated during Open MPI jobs.
See https://knem.gforge.inria.fr/ for details on Knem.
* Linux Cross-Memory Attach (CMA) or XPMEM is used by the `sm` shared
memory BTL when the CMA/XPMEM libraries are installed,
respectively. Linux CMA and XPMEM are similar (but different)
mechanisms for Open MPI to utilize single-copy semantics for shared
memory.
### Open MPI Extensions
An MPI "extensions" framework is included in Open MPI, but is not
enabled by default. See the "Open MPI API Extensions" section below
for more information on compiling and using MPI extensions.
The following extensions are included in this version of Open MPI:
1. `pcollreq`: Provides routines for persistent collective
communication operations and persistent neighborhood collective
communication operations, which are planned to be included in
MPI-4.0. The function names are prefixed with `MPIX_` instead of
`MPI_`, like `MPIX_Barrier_init`, because they are not
standardized yet. Future versions of Open MPI will switch to the
`MPI_` prefix once the MPI Standard which includes this feature is
published. See their man page for more details.
1. `shortfloat`: Provides MPI datatypes `MPIX_C_FLOAT16`,
`MPIX_SHORT_FLOAT`, `MPIX_SHORT_FLOAT`, and
`MPIX_CXX_SHORT_FLOAT_COMPLEX` if corresponding language types are
available. See `ompi/mpiext/shortfloat/README.txt` for details.
1. `affinity`: Provides the `OMPI_Affinity_str()` API, which returns
a string indicating the resources which a process is bound. For
more details, see its man page.
1. `cuda`: When the library is compiled with CUDA-aware support, it
provides two things. First, a macro
`MPIX_CUDA_AWARE_SUPPORT`. Secondly, the function
`MPIX_Query_cuda_support()` that can be used to query for support.
1. `example`: A non-functional extension; its only purpose is to
provide an example for how to create other extensions.
## Building Open MPI
If you have checked out a ***developer's copy*** of Open MPI (i.e.,
you cloned from Git), you really need to read the `HACKING` file
before attempting to build Open MPI. Really.
If you have downloaded a tarball, then things are much simpler.
Open MPI uses a traditional `configure` script paired with `make` to
build. Typical installs can be of the pattern:
```
shell$ ./configure [...options...]
shell$ make [-j N] all install
(use an integer value of N for parallel builds)
```
There are many available `configure` options (see `./configure --help`
for a full list); a summary of the more commonly used ones is included
below.
***NOTE:*** if you are building Open MPI on a network filesystem, the
machine you on which you are building *must* be time-synchronized with
the file server. Specifically: Open MPI's build system *requires*
accurate filesystem timestamps. If your `make` output includes
warning about timestamps in the future or runs GNU Automake, Autoconf,
and/or Libtool, this is *not normal*, and you may have an invalid
build. Ensure that the time on your build machine is synchronized
with the time on your file server, or build on a local filesystem.
Then remove the Open MPI source directory and start over (e.g., by
re-extracting the Open MPI tarball).
Note that for many of Open MPI's `--with-FOO` options, Open MPI will,
by default, search for header files and/or libraries for `FOO`. If
the relevant files are found, Open MPI will built support for `FOO`;
if they are not found, Open MPI will skip building support for `FOO`.
However, if you specify `--with-FOO` on the configure command line and
Open MPI is unable to find relevant support for `FOO`, configure will
assume that it was unable to provide a feature that was specifically
requested and will abort so that a human can resolve out the issue.
Additionally, if a search directory is specified in the form
`--with-FOO=DIR`, Open MPI will:
1. Search for `FOO`'s header files in `DIR/include`.
2. Search for `FOO`'s library files:
1. If `--with-FOO-libdir=<libdir>` was specified, search in
`<libdir>`.
1. Otherwise, search in `DIR/lib`, and if they are not found
there, search again in `DIR/lib64`.
3. If both the relevant header files and libraries are found:
1. Open MPI will build support for `FOO`.
1. If the root path where the FOO libraries are found is neither
`/usr` nor `/usr/local`, Open MPI will compile itself with
RPATH flags pointing to the directory where FOO's libraries
are located. Open MPI does not RPATH `/usr/lib[64]` and
`/usr/local/lib[64]` because many systems already search these
directories for run-time libraries by default; adding RPATH for
them could have unintended consequences for the search path
ordering.
### Installation Options
* `--prefix=DIR`:
Install Open MPI into the base directory named `DIR`. Hence, Open
MPI will place its executables in `DIR/bin`, its header files in
`DIR/include`, its libraries in `DIR/lib`, etc.
* `--disable-shared`:
By default, Open MPI and OpenSHMEM build shared libraries, and all
components are built as dynamic shared objects (DSOs). This switch
disables this default; it is really only useful when used with
`--enable-static`. Specifically, this option does *not* imply
`--enable-static`; enabling static libraries and disabling shared
libraries are two independent options.
* `--enable-static`:
Build MPI and OpenSHMEM as static libraries, and statically link in
all components. Note that this option does *not* imply
`--disable-shared`; enabling static libraries and disabling shared
libraries are two independent options.
Be sure to read the description of `--without-memory-manager`,
below; it may have some effect on `--enable-static`.
* `--disable-wrapper-rpath`:
By default, the wrapper compilers (e.g., `mpicc`) will enable
"rpath" support in generated executables on systems that support it.
That is, they will include a file reference to the location of Open
MPI's libraries in the application executable itself. This means
that the user does not have to set `LD_LIBRARY_PATH` to find Open
MPI's libraries (e.g., if they are installed in a location that the
run-time linker does not search by default).
On systems that utilize the GNU `ld` linker, recent enough versions
will actually utilize "runpath" functionality, not "rpath". There
is an important difference between the two:
1. "rpath": the location of the Open MPI libraries is hard-coded into
the MPI/OpenSHMEM application and cannot be overridden at
run-time.
1. "runpath": the location of the Open MPI libraries is hard-coded into
the MPI/OpenSHMEM application, but can be overridden at run-time
by setting the `LD_LIBRARY_PATH` environment variable.
For example, consider that you install Open MPI vA.B.0 and
compile/link your MPI/OpenSHMEM application against it. Later, you
install Open MPI vA.B.1 to a different installation prefix (e.g.,
`/opt/openmpi/A.B.1` vs. `/opt/openmpi/A.B.0`), and you leave the old
installation intact.
In the rpath case, your MPI application will always use the
libraries from your A.B.0 installation. In the runpath case, you
can set the `LD_LIBRARY_PATH` environment variable to point to the
A.B.1 installation, and then your MPI application will use those
libraries.
Note that in both cases, however, if you remove the original A.B.0
installation and set `LD_LIBRARY_PATH` to point to the A.B.1
installation, your application will use the A.B.1 libraries.
This rpath/runpath behavior can be disabled via
`--disable-wrapper-rpath`.
If you would like to keep the rpath option, but not enable runpath
a different configure option is avalabile
`--disable-wrapper-runpath`.
* `--enable-dlopen`:
Build all of Open MPI's components as standalone Dynamic Shared
Objects (DSO's) that are loaded at run-time (this is the default).
The opposite of this option, `--disable-dlopen`, causes two things:
1. All of Open MPI's components will be built as part of Open MPI's
normal libraries (e.g., `libmpi`).
1. Open MPI will not attempt to open any DSO's at run-time.
Note that this option does *not* imply that OMPI's libraries will be
built as static objects (e.g., `libmpi.a`). It only specifies the
location of OMPI's components: standalone DSOs or folded into the
Open MPI libraries. You can control whether Open MPI's libraries
are build as static or dynamic via `--enable|disable-static` and
`--enable|disable-shared`.
* `--disable-show-load-errors-by-default`:
Set the default value of the `mca_base_component_show_load_errors`
MCA variable: the `--enable` form of this option sets the MCA
variable to true, the `--disable` form sets the MCA variable to
false. The MCA `mca_base_component_show_load_errors` variable can
still be overridden at run time via the usual MCA-variable-setting
mechanisms; this configure option simply sets the default value.
The `--disable` form of this option is intended for Open MPI
packagers who tend to enable support for many different types of
networks and systems in their packages. For example, consider a
packager who includes support for both the FOO and BAR networks in
their Open MPI package, both of which require support libraries
(`libFOO.so` and `libBAR.so`). If an end user only has BAR
hardware, they likely only have `libBAR.so` available on their
systems -- not `libFOO.so`. Disabling load errors by default will
prevent the user from seeing potentially confusing warnings about
the FOO components failing to load because `libFOO.so` is not
available on their systems.
Conversely, system administrators tend to build an Open MPI that is
targeted at their specific environment, and contains few (if any)
components that are not needed. In such cases, they might want
their users to be warned that the FOO network components failed to
load (e.g., if `libFOO.so` was mistakenly unavailable), because Open
MPI may otherwise silently failover to a slower network path for MPI
traffic.
* `--with-platform=FILE`:
Load configure options for the build from `FILE`. Options on the
command line that are not in `FILE` are also used. Options on the
command line and in `FILE` are replaced by what is in `FILE`.
* `--with-libmpi-name=STRING`:
Replace `libmpi.*` and `libmpi_FOO.*` (where `FOO` is one of the
fortran supporting libraries installed in lib) with `libSTRING.*`
and `libSTRING_FOO.*`. This is provided as a convenience mechanism
for third-party packagers of Open MPI that might want to rename
these libraries for their own purposes. This option is *not*
intended for typical users of Open MPI.
* `--enable-mca-no-build=LIST`:
Comma-separated list of `<type>-<component>` pairs that will not be
built. For example, `--enable-mca-no-build=btl-portals,oob-ud` will
disable building the portals BTL and the ud OOB component.
### Networking support / options
* `--with-fca=DIR`:
Specify the directory where the Mellanox FCA library and
header files are located.
FCA is the support library for Mellanox switches and HCAs.
* `--with-hcoll=DIR`:
Specify the directory where the Mellanox hcoll library and header
files are located. This option is generally only necessary if the
hcoll headers and libraries are not in default compiler/linker
search paths.
hcoll is the support library for MPI collective operation offload on
Mellanox ConnectX-3 HCAs (and later).
* `--with-knem=DIR`:
Specify the directory where the knem libraries and header files are
located. This option is generally only necessary if the knem headers
and libraries are not in default compiler/linker search paths.
knem is a Linux kernel module that allows direct process-to-process
memory copies (optionally using hardware offload), potentially
increasing bandwidth for large messages sent between messages on the
same server. See [the Knem web site](https://knem.gforge.inria.fr/)
for details.
* `--with-libfabric=DIR`:
Specify the directory where the OpenFabrics Interfaces `libfabric`
library and header files are located. This option is generally only
necessary if the libfabric headers and libraries are not in default
compiler/linker search paths.
Libfabric is the support library for OpenFabrics Interfaces-based
network adapters, such as Cisco usNIC, Intel True Scale PSM, Cray
uGNI, etc.
* `--with-libfabric-libdir=DIR`:
Look in directory for the libfabric libraries. By default, Open MPI
will look in `DIR/lib` and `DIR/lib64`, which covers most cases.
This option is only needed for special configurations.
* `--with-portals4=DIR`:
Specify the directory where the Portals4 libraries and header files
are located. This option is generally only necessary if the Portals4
headers and libraries are not in default compiler/linker search
paths.
Portals is a low-level network API for high-performance networking
on high-performance computing systems developed by Sandia National
Laboratories, Intel Corporation, and the University of New Mexico.
The Portals 4 Reference Implementation is a complete implementation
of Portals 4, with transport over InfiniBand verbs and UDP.
* `--with-portals4-libdir=DIR`:
Location of libraries to link with for Portals4 support.
* `--with-portals4-max-md-size=SIZE` and
`--with-portals4-max-va-size=SIZE`:
Set configuration values for Portals 4
* `--with-psm=<directory>`:
Specify the directory where the QLogic InfiniPath / Intel True Scale
PSM library and header files are located. This option is generally
only necessary if the PSM headers and libraries are not in default
compiler/linker search paths.
PSM is the support library for QLogic InfiniPath and Intel TrueScale
network adapters.
* `--with-psm-libdir=DIR`:
Look in directory for the PSM libraries. By default, Open MPI will
look in `DIR/lib` and `DIR/lib64`, which covers most cases. This
option is only needed for special configurations.
* `--with-psm2=DIR`:
Specify the directory where the Intel Omni-Path PSM2 library and
header files are located. This option is generally only necessary
if the PSM2 headers and libraries are not in default compiler/linker
search paths.
PSM is the support library for Intel Omni-Path network adapters.
* `--with-psm2-libdir=DIR`:
Look in directory for the PSM2 libraries. By default, Open MPI will
look in `DIR/lib` and `DIR/lib64`, which covers most cases. This
option is only needed for special configurations.
* `--with-ucx=DIR`:
Specify the directory where the UCX libraries and header files are
located. This option is generally only necessary if the UCX headers
and libraries are not in default compiler/linker search paths.
* `--with-ucx-libdir=DIR`:
Look in directory for the UCX libraries. By default, Open MPI will
look in `DIR/lib` and `DIR/lib64`, which covers most cases. This
option is only needed for special configurations.
* `--with-usnic`:
Abort configure if Cisco usNIC support cannot be built.
### Run-time system support
* `--enable-mpirun-prefix-by-default`:
This option forces the `mpirun` command to always behave as if
`--prefix $prefix` was present on the command line (where `$prefix`
is the value given to the `--prefix` option to configure). This
prevents most `rsh`/`ssh`-based users from needing to modify their
shell startup files to set the `PATH` and/or `LD_LIBRARY_PATH` for
Open MPI on remote nodes. Note, however, that such users may still
desire to set `PATH` -- perhaps even in their shell startup files --
so that executables such as `mpicc` and `mpirun` can be found
without needing to type long path names.
* `--enable-orte-static-ports`:
Enable ORTE static ports for TCP OOB (default: enabled).
* `--with-alps`:
Force the building of for the Cray Alps run-time environment. If
Alps support cannot be found, configure will abort.
* `--with-lsf=DIR`:
Specify the directory where the LSF libraries and header files are
located. This option is generally only necessary if the LSF headers
and libraries are not in default compiler/linker search paths.
LSF is a resource manager system, frequently used as a batch
scheduler in HPC systems.
* `--with-lsf-libdir=DIR`:
Look in directory for the LSF libraries. By default, Open MPI will
look in `DIR/lib` and `DIR/lib64`, which covers most cases. This
option is only needed for special configurations.
* `--with-slurm`:
Force the building of SLURM scheduler support.
* `--with-sge`:
Specify to build support for the Oracle Grid Engine (OGE) resource
manager and/or the Open Grid Engine. OGE support is disabled by
default; this option must be specified to build OMPI's OGE support.
The Oracle Grid Engine (OGE) and open Grid Engine packages are
resource manager systems, frequently used as a batch scheduler in
HPC systems. It used to be called the "Sun Grid Engine", which is
why the option is still named `--with-sge`.
* `--with-tm=DIR`:
Specify the directory where the TM libraries and header files are
located. This option is generally only necessary if the TM headers
and libraries are not in default compiler/linker search paths.
TM is the support library for the Torque and PBS Pro resource
manager systems, both of which are frequently used as a batch
scheduler in HPC systems.
### Miscellaneous support libraries
* `--with-libevent(=VALUE)`
This option specifies where to find the libevent support headers and
library. The following `VALUE`s are permitted:
* `internal`: Use Open MPI's internal copy of libevent.
* `external`: Use an external Libevent installation (rely on default
compiler and linker paths to find it)
* `<no value>`: Same as `internal`.
* `DIR`: Specify the location of a specific libevent
installation to use
By default (or if `--with-libevent` is specified with no `VALUE`),
Open MPI will build and use the copy of libevent that it has in its
source tree. However, if the `VALUE` is `external`, Open MPI will
look for the relevant libevent header file and library in default
compiler / linker locations. Or, `VALUE` can be a directory tree
where the libevent header file and library can be found. This
option allows operating systems to include Open MPI and use their
default libevent installation instead of Open MPI's bundled
libevent.
libevent is a support library that provides event-based processing,
timers, and signal handlers. Open MPI requires libevent to build;
passing --without-libevent will cause configure to abort.
* `--with-libevent-libdir=DIR`:
Look in directory for the libevent libraries. This option is only
usable when building Open MPI against an external libevent
installation. Just like other `--with-FOO-libdir` configure
options, this option is only needed for special configurations.
* `--with-hwloc(=VALUE)`:
hwloc is a support library that provides processor and memory
affinity information for NUMA platforms. It is required by Open
MPI. Therefore, specifying `--with-hwloc=no` (or `--without-hwloc`)
is disallowed.
By default (i.e., if `--with-hwloc` is not specified, or if
`--with-hwloc` is specified without a value), Open MPI will first try
to find/use an hwloc installation on the current system. If Open
MPI cannot find one, it will fall back to build and use the internal
copy of hwloc included in the Open MPI source tree.
Alternatively, the `--with-hwloc` option can be used to specify
where to find the hwloc support headers and library. The following
`VALUE`s are permitted:
* `internal`: Only use Open MPI's internal copy of hwloc.
* `external`: Only use an external hwloc installation (rely on
default compiler and linker paths to find it).
* `DIR`: Only use the specific hwloc installation found in
the specified directory.
* `--with-hwloc-libdir=DIR`:
Look in directory for the hwloc libraries. This option is only
usable when building Open MPI against an external hwloc
installation. Just like other `--with-FOO-libdir` configure options,
this option is only needed for special configurations.
* `--disable-hwloc-pci`:
Disable building hwloc's PCI device-sensing capabilities. On some
platforms (e.g., SusE 10 SP1, x86-64), the libpci support library is
broken. Open MPI's configure script should usually detect when
libpci is not usable due to such brokenness and turn off PCI
support, but there may be cases when configure mistakenly enables
PCI support in the presence of a broken libpci. These cases may
result in `make` failing with warnings about relocation symbols in
libpci. The `--disable-hwloc-pci` switch can be used to force Open
MPI to not build hwloc's PCI device-sensing capabilities in these
cases.
Similarly, if Open MPI incorrectly decides that libpci is broken,
you can force Open MPI to build hwloc's PCI device-sensing
capabilities by using `--enable-hwloc-pci`.
hwloc can discover PCI devices and locality, which can be useful for
Open MPI in assigning message passing resources to MPI processes.
* `--with-libltdl=DIR`:
Specify the directory where the GNU Libtool libltdl libraries and
header files are located. This option is generally only necessary
if the libltdl headers and libraries are not in default
compiler/linker search paths.
Note that this option is ignored if `--disable-dlopen` is specified.
* `--disable-libompitrace`:
Disable building the simple `libompitrace` library (see note above
about libompitrace)
* `--with-valgrind(=DIR)`:
Directory where the valgrind software is installed. If Open MPI
finds Valgrind's header files, it will include additional support
for Valgrind's memory-checking debugger.
Specifically, it will eliminate a lot of false positives from
running Valgrind on MPI applications. There is a minor performance
penalty for enabling this option.
### MPI Functionality
* `--with-mpi-param-check(=VALUE)`:
Whether or not to check MPI function parameters for errors at
runtime. The following `VALUE`s are permitted:
* `always`: MPI function parameters are always checked for errors
* `never`: MPI function parameters are never checked for errors
* `runtime`: Whether MPI function parameters are checked depends on
the value of the MCA parameter `mpi_param_check` (default: yes).
* `yes`: Synonym for "always" (same as `--with-mpi-param-check`).
* `no`: Synonym for "never" (same as `--without-mpi-param-check`).
If `--with-mpi-param` is not specified, `runtime` is the default.
* `--disable-mpi-thread-multiple`:
Disable the MPI thread level `MPI_THREAD_MULTIPLE` (it is enabled by
default).
* `--enable-mpi-java`:
Enable building of an ***EXPERIMENTAL*** Java MPI interface
(disabled by default). You may also need to specify
`--with-jdk-dir`, `--with-jdk-bindir`, and/or `--with-jdk-headers`.
See [README.JAVA.md](README.JAVA.md) for details.
Note that this Java interface is ***INCOMPLETE*** (meaning: it does
not support all MPI functionality) and ***LIKELY TO CHANGE***. The
Open MPI developers would very much like to hear your feedback about
this interface. See [README.JAVA.md](README.JAVA.md) for more
details.
* `--enable-mpi-fortran(=VALUE)`:
By default, Open MPI will attempt to build all 3 Fortran bindings:
`mpif.h`, the `mpi` module, and the `mpi_f08` module. The following
`VALUE`s are permitted:
* `all`: Synonym for `yes`.
* `yes`: Attempt to build all 3 Fortran bindings; skip
any binding that cannot be built (same as
`--enable-mpi-fortran`).
* `mpifh`: Only build `mpif.h` support.
* `usempi`: Only build `mpif.h` and `mpi` module support.
* `usempif08`: Build `mpif.h`, `mpi` module, and `mpi_f08`
module support.
* `none`: Synonym for `no`.
* `no`: Do not build any MPI Fortran support (same as
`--disable-mpi-fortran`). This is mutually exclusive
with building the OpenSHMEM Fortran interface.
* `--enable-mpi-ext(=LIST)`:
Enable Open MPI's non-portable API extensions. `LIST` is a
comma-delmited list of extensions. If no `LIST` is specified, all
of the extensions are enabled.
See the "Open MPI API Extensions" section for more details.
* `--disable-mpi-io`:
Disable built-in support for MPI-2 I/O, likely because an
externally-provided MPI I/O package will be used. Default is to use
the internal framework system that uses the ompio component and a
specially modified version of ROMIO that fits inside the romio
component
* `--disable-io-romio`:
Disable the ROMIO MPI-IO component
* `--with-io-romio-flags=FLAGS`:
Pass `FLAGS` to the ROMIO distribution configuration script. This
option is usually only necessary to pass
parallel-filesystem-specific preprocessor/compiler/linker flags back
to the ROMIO system.
* `--disable-io-ompio`:
Disable the ompio MPI-IO component
* `--enable-sparse-groups`:
Enable the usage of sparse groups. This would save memory
significantly especially if you are creating large
communicators. (Disabled by default)
### OpenSHMEM Functionality
* `--disable-oshmem`:
Disable building the OpenSHMEM implementation (by default, it is
enabled).
* `--disable-oshmem-fortran`:
Disable building only the Fortran OpenSHMEM bindings. Please see
the "Compiler Notes" section herein which contains further
details on known issues with various Fortran compilers.
### Miscellaneous Functionality
* `--without-memory-manager`:
Disable building Open MPI's memory manager. Open MPI's memory
manager is usually built on Linux based platforms, and is generally
only used for optimizations with some OpenFabrics-based networks (it
is not *necessary* for OpenFabrics networks, but some performance
loss may be observed without it).
However, it may be necessary to disable the memory manager in order
to build Open MPI statically.
* `--with-ft=TYPE`:
Specify the type of fault tolerance to enable. Options: LAM
(LAM/MPI-like), cr (Checkpoint/Restart). Fault tolerance support is
disabled unless this option is specified.
* `--enable-peruse`:
Enable the PERUSE MPI data analysis interface.
* `--enable-heterogeneous`:
Enable support for running on heterogeneous clusters (e.g., machines
with different endian representations). Heterogeneous support is
disabled by default because it imposes a minor performance penalty.
***THIS FUNCTIONALITY IS CURRENTLY BROKEN - DO NOT USE***
* `--with-wrapper-cflags=CFLAGS`
* `--with-wrapper-cxxflags=CXXFLAGS`
* `--with-wrapper-fflags=FFLAGS`
* `--with-wrapper-fcflags=FCFLAGS`
* `--with-wrapper-ldflags=LDFLAGS`
* `--with-wrapper-libs=LIBS`:
Add the specified flags to the default flags that are used in Open
MPI's "wrapper" compilers (e.g., `mpicc` -- see below for more
information about Open MPI's wrapper compilers). By default, Open
MPI's wrapper compilers use the same compilers used to build Open
MPI and specify a minimum set of additional flags that are necessary
to compile/link MPI applications. These configure options give
system administrators the ability to embed additional flags in
OMPI's wrapper compilers (which is a local policy decision). The
meanings of the different flags are:
`CFLAGS`: Flags passed by the `mpicc` wrapper to the C compiler
`CXXFLAGS`: Flags passed by the `mpic++` wrapper to the C++ compiler
`FCFLAGS`: Flags passed by the `mpifort` wrapper to the Fortran compiler
`LDFLAGS`: Flags passed by all the wrappers to the linker
`LIBS`: Flags passed by all the wrappers to the linker
There are other ways to configure Open MPI's wrapper compiler
behavior; see [the Open MPI FAQ](https://www.open-mpi.org/faq/) for
more information.
There are many other options available -- see `./configure --help`.
Changing the compilers that Open MPI uses to build itself uses the
standard Autoconf mechanism of setting special environment variables
either before invoking configure or on the configure command line.
The following environment variables are recognized by configure:
* `CC`: C compiler to use
* `CFLAGS`: Compile flags to pass to the C compiler
* `CPPFLAGS`: Preprocessor flags to pass to the C compiler
* `CXX`: C++ compiler to use
* `CXXFLAGS`: Compile flags to pass to the C++ compiler
* `CXXCPPFLAGS`: Preprocessor flags to pass to the C++ compiler
* `FC`: Fortran compiler to use
* `FCFLAGS`: Compile flags to pass to the Fortran compiler
* `LDFLAGS`: Linker flags to pass to all compilers
* `LIBS`: Libraries to pass to all compilers (it is rarely
necessary for users to need to specify additional `LIBS`)
* `PKG_CONFIG`: Path to the `pkg-config` utility
For example:
```
shell$ ./configure CC=mycc CXX=myc++ FC=myfortran ...
```
***NOTE:*** We generally suggest using the above command line form for
setting different compilers (vs. setting environment variables and
then invoking `./configure`). The above form will save all variables
and values in the `config.log` file, which makes post-mortem analysis
easier if problems occur.
Note that if you intend to compile Open MPI with a `make` other than
the default one in your `PATH`, then you must either set the `$MAKE`
environment variable before invoking Open MPI's `configure` script, or
pass `MAKE=your_make_prog` to configure. For example:
```
shell$ ./configure MAKE=/path/to/my/make ...
```
This could be the case, for instance, if you have a shell alias for
`make`, or you always type `gmake` out of habit. Failure to tell
`configure` which non-default `make` you will use to compile Open MPI
can result in undefined behavior (meaning: don't do that).
Note that you may also want to ensure that the value of
`LD_LIBRARY_PATH` is set appropriately (or not at all) for your build
(or whatever environment variable is relevant for your operating
system). For example, some users have been tripped up by setting to
use a non-default Fortran compiler via the `FC` environment variable,
but then failing to set `LD_LIBRARY_PATH` to include the directory
containing that non-default Fortran compiler's support libraries.
This causes Open MPI's `configure` script to fail when it tries to
compile / link / run simple Fortran programs.
It is required that the compilers specified be compile and link
compatible, meaning that object files created by one compiler must be
able to be linked with object files from the other compilers and
produce correctly functioning executables.
Open MPI supports all the `make` targets that are provided by GNU
Automake, such as:
* `all`: build the entire Open MPI package
* `install`: install Open MPI
* `uninstall`: remove all traces of Open MPI from the $prefix
* `clean`: clean out the build tree
Once Open MPI has been built and installed, it is safe to run `make
clean` and/or remove the entire build tree.
VPATH and parallel builds are fully supported.
Generally speaking, the only thing that users need to do to use Open
MPI is ensure that `PREFIX/bin` is in their `PATH` and `PREFIX/lib` is
in their `LD_LIBRARY_PATH`. Users may need to ensure to set the
`PATH` and `LD_LIBRARY_PATH` in their shell setup files (e.g.,
`.bashrc`, `.cshrc`) so that non-interactive `rsh`/`ssh`-based logins
will be able to find the Open MPI executables.
## Open MPI Version Numbers and Binary Compatibility
Open MPI has two sets of version numbers that are likely of interest
to end users / system administrator:
1. Software version number
1. Shared library version numbers
Both are predicated on Open MPI's definition of "backwards
compatibility."
***NOTE:*** The version numbering conventions were changed with the
release of v1.10.0. Most notably, Open MPI no longer uses an
"odd/even" release schedule to indicate feature development vs. stable
releases. See the README in releases prior to v1.10.0 for more
information (e.g.,
https://github.com/open-mpi/ompi/blob/v1.8/README#L1392-L1475).
### Backwards Compatibility
Open MPI version Y is backwards compatible with Open MPI version X
(where Y>X) if users can:
* Compile an MPI/OpenSHMEM application with version X,
`mpirun`/`oshrun` it with version Y, and get the same
user-observable behavior.
* Invoke `ompi_info` with the same CLI options in versions X and Y and
get the same user-observable behavior.
Note that this definition encompasses several things:
* Application Binary Interface (ABI)
* MPI / OpenSHMEM run time system
* `mpirun` / `oshrun` command line options
* MCA parameter names / values / meanings
However, this definition only applies when the same version of Open
MPI is used with all instances of the runtime and MPI / OpenSHMEM
processes in a single MPI job. If the versions are not exactly the
same everywhere, Open MPI is not guaranteed to work properly in any
scenario.
Backwards compatibility tends to work best when user applications are
dynamically linked to one version of the Open MPI / OSHMEM libraries,
and can be updated at run time to link to a new version of the Open
MPI / OSHMEM libraries.
For example, if an MPI / OSHMEM application links statically against
the libraries from Open MPI vX, then attempting to launch that
application with `mpirun` / `oshrun` from Open MPI vY is not guaranteed to
work (because it is mixing vX and vY of Open MPI in a single job).
Similarly, if using a container technology that internally bundles all
the libraries from Open MPI vX, attempting to launch that container
with `mpirun` / `oshrun` from Open MPI vY is not guaranteed to work.
### Software Version Number
Official Open MPI releases use the common "A.B.C" version identifier
format. Each of the three numbers has a specific meaning:
* Major: The major number is the first integer in the version string
Changes in the major number typically indicate a significant
change in the code base and/or end-user functionality, and also
indicate a break from backwards compatibility. Specifically: Open
MPI releases with different major version numbers are not
backwards compatibale with each other.
***CAVEAT:*** This rule does not extend to versions prior to v1.10.0.
Specifically: v1.10.x is not guaranteed to be backwards
compatible with other v1.x releases.
* Minor: The minor number is the second integer in the version string.
Changes in the minor number indicate a user-observable change in the
code base and/or end-user functionality. Backwards compatibility
will still be preserved with prior releases that have the same major
version number (e.g., v2.5.3 is backwards compatible with v2.3.1).
* Release: The release number is the third integer in the version
string. Changes in the release number typically indicate a bug fix
in the code base and/or end-user functionality. For example, if
there is a release that only contains bug fixes and no other
user-observable changes or new features, only the third integer will
be increased (e.g., from v4.3.0 to v4.3.1).
The "A.B.C" version number may optionally be followed by a Quantifier:
* Quantifier: Open MPI version numbers sometimes have an arbitrary
string affixed to the end of the version number. Common strings
include:
* aX: Indicates an alpha release. X is an integer indicating the
number of the alpha release (e.g., v1.10.3a5 indicates the 5th
alpha release of version 1.10.3).
* bX: Indicates a beta release. X is an integer indicating the
number of the beta release (e.g., v1.10.3b3 indicates the 3rd beta
release of version 1.10.3).
* rcX: Indicates a release candidate. X is an integer indicating the
number of the release candidate (e.g., v1.10.3rc4 indicates the
4th release candidate of version 1.10.3).
Nightly development snapshot tarballs use a different version number
scheme; they contain three distinct values:
* The git branch name from which the tarball was created.
* The date/timestamp, in `YYYYMMDDHHMM` format.
* The hash of the git commit from which the tarball was created.
For example, a snapshot tarball filename of
`openmpi-v2.x-201703070235-e4798fb.tar.gz` indicates that this tarball
was created from the v2.x branch, on March 7, 2017, at 2:35am GMT,
from git hash e4798fb.
### Shared Library Version Number
The GNU Libtool official documentation details how the versioning
scheme works. The quick version is that the shared library versions
are a triple of integers: (current,revision,age), or `c:r:a`. This
triple is not related to the Open MPI software version number. There
are six simple rules for updating the values (taken almost verbatim
from the Libtool docs):
1. Start with version information of `0:0:0` for each shared library.
1. Update the version information only immediately before a public
release of your software. More frequent updates are unnecessary,
and only guarantee that the current interface number gets larger
faster.
1. If the library source code has changed at all since the last
update, then increment revision (`c:r:a` becomes `c:r+1:a`).
1. If any interfaces have been added, removed, or changed since the
last update, increment current, and set revision to 0.
1. If any interfaces have been added since the last public release,
then increment age.
1. If any interfaces have been removed since the last public release,
then set age to 0.
Here's how we apply those rules specifically to Open MPI:
1. The above rules do not apply to MCA components (a.k.a. "plugins");
MCA component `.so` versions stay unspecified.
1. The above rules apply exactly as written to the following libraries
starting with Open MPI version v1.5 (prior to v1.5, `libopen-pal`
and `libopen-rte` were still at `0:0:0` for reasons discussed in bug
ticket #2092 https://svn.open-mpi.org/trac/ompi/ticket/2092):
* `libopen-rte`
* `libopen-pal`
* `libmca_common_*`
1. The following libraries use a slightly modified version of the
above rules: rules 4, 5, and 6 only apply to the official MPI and
OpenSHMEM interfaces (functions, global variables). The rationale
for this decision is that the vast majority of our users only care
about the official/public MPI/OpenSHMEM interfaces; we therefore
want the `.so` version number to reflect only changes to the
official MPI/OpenSHMEM APIs. Put simply: non-MPI/OpenSHMEM API /
internal changes to the MPI-application-facing libraries are
irrelevant to pure MPI/OpenSHMEM applications.
* `libmpi`
* `libmpi_mpifh`
* `libmpi_usempi_tkr`
* `libmpi_usempi_ignore_tkr`
* `libmpi_usempif08`
* `libmpi_cxx`
* `libmpi_java`
* `liboshmem`
## Checking Your Open MPI Installation
The `ompi_info` command can be used to check the status of your Open
MPI installation (located in `PREFIX/bin/ompi_info`). Running it with
no arguments provides a summary of information about your Open MPI
installation.
Note that the `ompi_info` command is extremely helpful in determining
which components are installed as well as listing all the run-time
settable parameters that are available in each component (as well as
their default values).
The following options may be helpful:
* `--all`: Show a *lot* of information about your Open MPI
installation.
* `--parsable`: Display all the information in an easily
`grep`/`cut`/`awk`/`sed`-able format.
* `--param FRAMEWORK COMPONENT`:
A `FRAMEWORK` value of `all` and a `COMPONENT` value of `all` will
show all parameters to all components. Otherwise, the parameters of
all the components in a specific framework, or just the parameters
of a specific component can be displayed by using an appropriate
FRAMEWORK and/or COMPONENT name.
* `--level LEVEL`:
By default, `ompi_info` only shows "Level 1" MCA parameters --
parameters that can affect whether MPI processes can run
successfully or not (e.g., determining which network interfaces to
use). The `--level` option will display all MCA parameters from
level 1 to `LEVEL` (the max `LEVEL` value is 9). Use `ompi_info
--param FRAMEWORK COMPONENT --level 9` to see *all* MCA parameters
for a given component. See "The Modular Component Architecture
(MCA)" section, below, for a fuller explanation.
Changing the values of these parameters is explained in the "The
Modular Component Architecture (MCA)" section, below.
When verifying a new Open MPI installation, we recommend running six
tests:
1. Use `mpirun` to launch a non-MPI program (e.g., `hostname` or
`uptime`) across multiple nodes.
1. Use `mpirun` to launch a trivial MPI program that does no MPI
communication (e.g., the `hello_c` program in the `examples/`
directory in the Open MPI distribution).
1. Use `mpirun` to launch a trivial MPI program that sends and
receives a few MPI messages (e.g., the `ring_c` program in the
`examples/` directory in the Open MPI distribution).
1. Use `oshrun` to launch a non-OpenSHMEM program across multiple
nodes.
1. Use `oshrun` to launch a trivial MPI program that does no OpenSHMEM
communication (e.g., `hello_shmem.c` program in the `examples/`
directory in the Open MPI distribution.)
1. Use `oshrun` to launch a trivial OpenSHMEM program that puts and
gets a few messages (e.g., the `ring_shmem.c` in the `examples/`
directory in the Open MPI distribution.)
If you can run all six of these tests successfully, that is a good
indication that Open MPI built and installed properly.
## Open MPI API Extensions
Open MPI contains a framework for extending the MPI API that is
available to applications. Each extension is usually a standalone set
of functionality that is distinct from other extensions (similar to
how Open MPI's plugins are usually unrelated to each other). These
extensions provide new functions and/or constants that are available
to MPI applications.
WARNING: These extensions are neither standard nor portable to other
MPI implementations!
### Compiling the extensions
Open MPI extensions are all enabled by default; they can be disabled
via the `--disable-mpi-ext` command line switch.
Since extensions are meant to be used by advanced users only, this
file does not document which extensions are available or what they
do. Look in the ompi/mpiext/ directory to see the extensions; each
subdirectory of that directory contains an extension. Each has a
README file that describes what it does.
### Using the extensions
To reinforce the fact that these extensions are non-standard, you must
include a separate header file after `<mpi.h>` to obtain the function
prototypes, constant declarations, etc. For example:
```c
#include <mpi.h>
#if defined(OPEN_MPI) && OPEN_MPI
#include <mpi-ext.h>
#endif
int main() {
MPI_Init(NULL, NULL);
#if defined(OPEN_MPI) && OPEN_MPI
{
char ompi_bound[OMPI_AFFINITY_STRING_MAX];
char current_binding[OMPI_AFFINITY_STRING_MAX];
char exists[OMPI_AFFINITY_STRING_MAX];
OMPI_Affinity_str(OMPI_AFFINITY_LAYOUT_FMT, ompi_bound,
current_bindings, exists);
}
#endif
MPI_Finalize();
return 0;
}
```
Notice that the Open MPI-specific code is surrounded by the `#if`
statement to ensure that it is only ever compiled by Open MPI.
The Open MPI wrapper compilers (`mpicc` and friends) should
automatically insert all relevant compiler and linker flags necessary
to use the extensions. No special flags or steps should be necessary
compared to "normal" MPI applications.
## Compiling Open MPI Applications
Open MPI provides "wrapper" compilers that should be used for
compiling MPI and OpenSHMEM applications:
* C: `mpicc`, `oshcc`
* C++: `mpiCC`, `oshCC` (or `mpic++` if your filesystem is case-insensitive)
* Fortran: `mpifort`, `oshfort`
For example:
```
shell$ mpicc hello_world_mpi.c -o hello_world_mpi -g
shell$
```
For OpenSHMEM applications:
```
shell$ oshcc hello_shmem.c -o hello_shmem -g
shell$
```
All the wrapper compilers do is add a variety of compiler and linker
flags to the command line and then invoke a back-end compiler. To be
specific: the wrapper compilers do not parse source code at all; they
are solely command-line manipulators, and have nothing to do with the
actual compilation or linking of programs. The end result is an MPI
executable that is properly linked to all the relevant libraries.
Customizing the behavior of the wrapper compilers is possible (e.g.,
changing the compiler [not recommended] or specifying additional
compiler/linker flags); see the Open MPI FAQ for more information.
Alternatively, Open MPI also installs `pkg-config(1)` configuration
files under `$libdir/pkgconfig`. If `pkg-config` is configured to find
these files, then compiling / linking Open MPI programs can be
performed like this:
```
shell$ gcc hello_world_mpi.c -o hello_world_mpi -g \
`pkg-config ompi-c --cflags --libs`
shell$
```
Open MPI supplies multiple `pkg-config(1)` configuration files; one
for each different wrapper compiler (language):
* `ompi`: Synonym for `ompi-c`; Open MPI applications using the C
MPI bindings
* `ompi-c`: Open MPI applications using the C MPI bindings
* `ompi-cxx`: Open MPI applications using the C MPI bindings
* `ompi-fort`: Open MPI applications using the Fortran MPI bindings
The following `pkg-config(1)` configuration files *may* be installed,
depending on which command line options were specified to Open MPI's
configure script. They are not necessary for MPI applications, but
may be used by applications that use Open MPI's lower layer support
libraries.
* `opal`: Open Portable Access Layer applications
## Running Open MPI Applications
Open MPI supports both `mpirun` and `mpiexec` (they are exactly
equivalent) to launch MPI applications. For example:
```
shell$ mpirun -np 2 hello_world_mpi
or
shell$ mpiexec -np 1 hello_world_mpi : -np 1 hello_world_mpi
```
are equivalent.
The `rsh` launcher (which defaults to using `ssh`) accepts a
`--hostfile` parameter (the option `--machinefile` is equivalent); you
can specify a `--hostfile` parameter indicating a standard
`mpirun`-style hostfile (one hostname per line):
```
shell$ mpirun --hostfile my_hostfile -np 2 hello_world_mpi
```
If you intend to run more than one process on a node, the hostfile can
use the "slots" attribute. If "slots" is not specified, a count of 1
is assumed. For example, using the following hostfile:
```
shell$ cat my_hostfile
node1.example.com
node2.example.com
node3.example.com slots=2
node4.example.com slots=4
```
```
shell$ mpirun --hostfile my_hostfile -np 8 hello_world_mpi
```
will launch `MPI_COMM_WORLD` rank 0 on node1, rank 1 on node2, ranks 2
and 3 on node3, and ranks 4 through 7 on node4.
Other starters, such as the resource manager / batch scheduling
environments, do not require hostfiles (and will ignore the hostfile
if it is supplied). They will also launch as many processes as slots
have been allocated by the scheduler if no "-np" argument has been
provided. For example, running a SLURM job with 8 processors:
```
shell$ salloc -n 8 mpirun a.out
```
The above command will reserve 8 processors and run 1 copy of mpirun,
which will, in turn, launch 8 copies of a.out in a single
`MPI_COMM_WORLD` on the processors that were allocated by SLURM.
Note that the values of component parameters can be changed on the
`mpirun` / `mpiexec` command line. This is explained in the section
below, "The Modular Component Architecture (MCA)".
Open MPI supports `oshrun` to launch OpenSHMEM applications. For
example:
```
shell$ oshrun -np 2 hello_world_oshmem
```
OpenSHMEM applications may also be launched directly by resource
managers such as SLURM. For example, when OMPI is configured
`--with-pmix` and `--with-slurm`, one may launch OpenSHMEM applications
via `srun`:
```
shell$ srun -N 2 hello_world_oshmem
```
## The Modular Component Architecture (MCA)
The MCA is the backbone of Open MPI -- most services and functionality
are implemented through MCA components.
### MPI layer frameworks
Here is a list of all the component frameworks in the MPI layer of
Open MPI:
* `bml`: BTL management layer
* `coll`: MPI collective algorithms
* `fbtl`: file byte transfer layer: abstraction for individual
read: collective read and write operations for MPI I/O
* `fs`: file system functions for MPI I/O
* `io`: MPI I/O
* `mtl`: Matching transport layer, used for MPI point-to-point
messages on some types of networks
* `op`: Back end computations for intrinsic MPI_Op operators
* `osc`: MPI one-sided communications
* `pml`: MPI point-to-point management layer
* `rte`: Run-time environment operations
* `sharedfp`: shared file pointer operations for MPI I/O
* `topo`: MPI topology routines
* `vprotocol`: Protocols for the "v" PML
### OpenSHMEM component frameworks
* `atomic`: OpenSHMEM atomic operations
* `memheap`: OpenSHMEM memory allocators that support the
PGAS memory model
* `scoll`: OpenSHMEM collective operations
* `spml`: OpenSHMEM "pml-like" layer: supports one-sided,
point-to-point operations
* `sshmem`: OpenSHMEM shared memory backing facility
### Back-end run-time environment (RTE) component frameworks:
* `dfs`: Distributed file system
* `errmgr`: RTE error manager
* `ess`: RTE environment-specific services
* `filem`: Remote file management
* `grpcomm`: RTE group communications
* `iof`: I/O forwarding
* `notifier`: System-level notification support
* `odls`: OpenRTE daemon local launch subsystem
* `oob`: Out of band messaging
* `plm`: Process lifecycle management
* `ras`: Resource allocation system
* `rmaps`: Resource mapping system
* `rml`: RTE message layer
* `routed`: Routing table for the RML
* `rtc`: Run-time control framework
* `schizo`: OpenRTE personality framework
* `state`: RTE state machine
### Miscellaneous frameworks:
* `allocator`: Memory allocator
* `backtrace`: Debugging call stack backtrace support
* `btl`: Point-to-point Byte Transfer Layer
* `dl`: Dynamic loading library interface
* `event`: Event library (libevent) versioning support
* `hwloc`: Hardware locality (hwloc) versioning support
* `if`: OS IP interface support
* `installdirs`: Installation directory relocation services
* `memchecker`: Run-time memory checking
* `memcpy`: Memory copy support
* `memory`: Memory management hooks
* `mpool`: Memory pooling
* `patcher`: Symbol patcher hooks
* `pmix`: Process management interface (exascale)
* `pstat`: Process status
* `rcache`: Memory registration cache
* `sec`: Security framework
* `shmem`: Shared memory support (NOT related to OpenSHMEM)
* `timer`: High-resolution timers
### Framework notes
Each framework typically has one or more components that are used at
run-time. For example, the `btl` framework is used by the MPI layer
to send bytes across different types underlying networks. The `tcp`
`btl`, for example, sends messages across TCP-based networks; the
`ucx` `pml` sends messages across InfiniBand-based networks.
Each component typically has some tunable parameters that can be
changed at run-time. Use the `ompi_info` command to check a component
to see what its tunable parameters are. For example:
```
shell$ ompi_info --param btl tcp
```
shows some of the parameters (and default values) for the `tcp` `btl`
component (use `--level` to show *all* the parameters; see below).
Note that `ompi_info` only shows a small number a component's MCA
parameters by default. Each MCA parameter has a "level" value from 1
to 9, corresponding to the MPI-3 MPI_T tool interface levels. In Open
MPI, we have interpreted these nine levels as three groups of three:
1. End user / basic
1. End user / detailed
1. End user / all
1. Application tuner / basic
1. Application tuner / detailed
1. Application tuner / all
1. MPI/OpenSHMEM developer / basic
1. MPI/OpenSHMEM developer / detailed
1. MPI/OpenSHMEM developer / all
Here's how the three sub-groups are defined:
1. End user: Generally, these are parameters that are required for
correctness, meaning that someone may need to set these just to
get their MPI/OpenSHMEM application to run correctly.
1. Application tuner: Generally, these are parameters that can be
used to tweak MPI application performance.
1. MPI/OpenSHMEM developer: Parameters that either don't fit in the
other two, or are specifically intended for debugging /
development of Open MPI itself.
Each sub-group is broken down into three classifications:
1. Basic: For parameters that everyone in this category will want to
see.
1. Detailed: Parameters that are useful, but you probably won't need
to change them often.
1. All: All other parameters -- probably including some fairly
esoteric parameters.
To see *all* available parameters for a given component, specify that
ompi_info should use level 9:
```
shell$ ompi_info --param btl tcp --level 9
```
These values can be overridden at run-time in several ways. At
run-time, the following locations are examined (in order) for new
values of parameters:
1. `PREFIX/etc/openmpi-mca-params.conf`:
This file is intended to set any system-wide default MCA parameter
values -- it will apply, by default, to all users who use this Open
MPI installation. The default file that is installed contains many
comments explaining its format.
1. `$HOME/.openmpi/mca-params.conf`:
If this file exists, it should be in the same format as
`PREFIX/etc/openmpi-mca-params.conf`. It is intended to provide
per-user default parameter values.
1. environment variables of the form `OMPI_MCA_<name>` set equal to a
`VALUE`:
Where `<name>` is the name of the parameter. For example, set the
variable named `OMPI_MCA_btl_tcp_frag_size` to the value 65536
(Bourne-style shells):
```
shell$ OMPI_MCA_btl_tcp_frag_size=65536
shell$ export OMPI_MCA_btl_tcp_frag_size
```
4. the `mpirun`/`oshrun` command line: `--mca NAME VALUE`
Where <name> is the name of the parameter. For example:
```
shell$ mpirun --mca btl_tcp_frag_size 65536 -np 2 hello_world_mpi
```
These locations are checked in order. For example, a parameter value
passed on the `mpirun` command line will override an environment
variable; an environment variable will override the system-wide
defaults.
Each component typically activates itself when relevant. For example,
the usNIC component will detect that usNIC devices are present and
will automatically be used for MPI communications. The SLURM
component will automatically detect when running inside a SLURM job
and activate itself. And so on.
Components can be manually activated or deactivated if necessary, of
course. The most common components that are manually activated,
deactivated, or tuned are the `btl` components -- components that are
used for MPI point-to-point communications on many types common
networks.
For example, to *only* activate the `tcp` and `self` (process loopback)
components are used for MPI communications, specify them in a
comma-delimited list to the `btl` MCA parameter:
```
shell$ mpirun --mca btl tcp,self hello_world_mpi
```
To add shared memory support, add `sm` into the command-delimited list
(list order does not matter):
```
shell$ mpirun --mca btl tcp,sm,self hello_world_mpi
```
(there used to be a `vader` BTL for shared memory support; it was
renamed to `sm` in Open MPI v5.0.0, but the alias `vader` still works
as well)
To specifically deactivate a specific component, the comma-delimited
list can be prepended with a `^` to negate it:
```
shell$ mpirun --mca btl ^tcp hello_mpi_world
```
The above command will use any other `btl` component other than the
`tcp` component.
## Questions? Problems?
Found a bug? Got a question? Want to make a suggestion? Want to
contribute to Open MPI? Please let us know!
When submitting questions and problems, be sure to include as much
extra information as possible. [See the community help web
page](https://www.open-mpi.org/community/help/) for details on all the
information that we request in order to provide assistance:
The best way to report bugs, send comments, or ask questions is to
sign up on the user's and/or developer's mailing list (for user-level
and developer-level questions; when in doubt, send to the user's
list):
* users@lists.open-mpi.org
* devel@lists.open-mpi.org
Because of spam, only subscribers are allowed to post to these lists
(ensure that you subscribe with and post from exactly the same e-mail
address -- joe@example.com is considered different than
joe@mycomputer.example.com!). Visit these pages to subscribe to the
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* [Subscribe to the users mailing
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