4.14. Advice for packagers
4.14.1. Do not use Open MPI’s internal dependent libraries
The Open MPI community strongly suggests that binary Open MPI packages should not include Hwloc, Libevent, PMIx, or PRRTE. Although several of these libraries are required by Open MPI (and are therefore bundled in the Open MPI source code distribution for end-user convenience), binary Open MPI packages should limit themselves solely to Open MPI artifacts. Specifically: ensure to configure and build Open MPI against external installations of these required packages.
Packagers may therefore wish to configure Open MPI with something like the following:
# Install Sphinx so that Open MPI can re-build its docs with the
# installed PRRTE's docs
pip install docs/requirements.txt
./configure --with-libevent=external --with-hwloc=external \
--with-pmix=external --with-prrte=external ...
Note the installation of the Sphinx tool so that Open MPI can re-build its documentation with the external PRRTE’s documentation.
Failure to do this will mean Open MPI’s documentation will be correct for the version of PRRTE that is bundled in the Open MPI distribution, but may not be entirely correct for the version of PRRTE that you are building against.
external keywords will force Open MPI’s
ignore all the bundled libraries and only look for external versions
of these support libraries. This also has the benefit of causing
configure to fail if it cannot find the required support libraries
outside of the Open MPI source tree — a good sanity check to
ensure that your package is correctly relying on the
independently-built and installed versions.
See this section for more
information about the required support library
4.14.2. Have Sphinx installed
Since you should be (will be) installing Open MPI against an external
PRRTE and PMIx, you should have Sphinx installed before running Open MPI’s
This will allow Open MPI to (re-)build its documentation according to the PMIx and PRRTE that you are building against.
To be clear: the Open MPI distribution tarball comes with pre-built documentation — rendered in HTML and nroff — that is suitable for the versions of PRRTE and PMIx that are bundled in that tarball.
However, if you are building Open MPI against not-bundled versions of
PRRTE / PMIx (as all packagers should be), Open MPI needs to re-build
its documentation with specific information from those external PRRTE
/ PMIx installs. For that, you need to have Sphinx installed before
running Open MPI’s
4.14.3. Components (“plugins”): DSO or no?
Open MPI contains a large number of components (sometimes called “plugins”) to effect different types of functionality in MPI. For example, some components effect Open MPI’s networking functionality: they may link against specialized libraries to provide highly-optimized network access.
Open MPI v5.0.0 has two
configure-time defaults regarding the
treatment of components that may be of interest to packagers:
Open MPI’s libraries default to building as shared libraries (vs. static libraries). For example, on Linux, Open MPI will default to building
Open MPI will default to including its components in its libraries (as opposed to being compiled as dynamic shared objects, or DSOs). For example,
libmpi.soon Linux systems will contain the UCX PML component, instead of the UCX PML being compiled into
mca_pml_ucx.soand dynamically opened at run time via
See the descriptions of
--enable-mca-staticin this section for more details about how to change this defaults.
A side effect of these two defaults is that all the components
included in the Open MPI libraries will bring their dependencies with
them. For example (on Linux), if the XYZ PML component in the MPI
libXYZ.so, then these defaults mean that
libmpi.so will depend on
libXYZ.so. This dependency will
likely be telegraphed into the Open MPI binary package that includes
Conversely, if the XYZ PML component was built as a DSO, then —
assuming no other parts of Open MPI require
libmpi.so would not be dependent on
libXYZ.so. Instead, the
mca_pml_xyz.so DSO would have the dependency upon
Packagers can use these facts to potentially create multiple binary
Open MPI packages, each with different dependencies by, for example,
--enable-mca-dso to selectively build some components as
DSOs and leave the others included in their respective Open MPI
# Build all the "accelerator" components as DSOs (all other
# components will default to being built in their respective
shell$ ./configure --enable-mca-dso=accelerator ...
This allows packaging
$libdir as part of the “main” Open MPI
binary package, but then packaging
$libdir/openmpi/mca_accelerator_*.so as sub-packages. These
sub-packages may inherit dependencies on the CUDA and/or ROCM
packages, for example. User can always install the “main” Open MPI
binary package, and can install the additional “accelerator” Open MPI
binary sub-package if they actually have accelerator hardware
installed (which will cause the installation of additional