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:
./configure --with-libevent=external --with-hwloc=external \ --with-pmix=external --with-prrte=external ...
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. 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 head of development 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
See the descriptions of
--enable-staticin this section for more details about how to change this default.
Also be sure to see this warning about building static apps.
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 # libraries) 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