# 4.8.2. Installation options

The following are general installation command line options that can be used with `configure`:

- `--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.

  Note

  Also see the section on installation location for more information on the installation prefix.

- `--disable-shared`: By default, Open MPI and OpenSHMEM build shared libraries, and all components are included as part of those shared libraries. 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.

  Tip

  See this section for advice to packagers about this CLI option.

- `--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`.

  Tip

  See this section for advice to packagers about this CLI option.

- `--disable-wrapper-runpath` / `--disable-wrapper-rpath`: By default, the wrapper compilers (e.g., `mpicc`) will explicitly add “runpath” and “rpath” linker flags when linking user executables on systems that support them. That is, the created executables will include a filesystem path 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, which can be helpful if they are installed in a location that the run-time linker does not search by default.

  Using the `--disable-wrapper-r*path` options will prevent the wrappers from explicitly adding one or both of these linker flags.

  Note

  By default, the wrapper compilers prefer “runpath” behavior over “rpath” behavior.

  - Using `--disable-wrapper-runpath` alters this preference: explicit “runpath” linker flags will not be added by the wrappers. However, “rpath” flags may still be added, if the platform supports them.

  - Using both `--disable-wrapper-runpath` and `--disable-wrapper-rpath` will prevent the wrappers from explicitly adding “runpath” and “rpath” linker flags.

  Caution

  Even if the wrapper compilers do not explicitly add “runpath” or “rpath” linker flags, the local compiler, linker, and/or operating system may implicitly enable either “runpath” or “rpath” behavior when linking.

  Important

  The `--disable-wrapper-runpath` and `--disable-wrapper-rpath` CLI options only affect the flags that the wrapper compilers use when building MPI/SHMEM applications. These options do not affect how Open MPI or OpenSHMEM are built (to include the wrapper compilers themselves).

  See the Linker “rpath” and “runpath” functionality section for details on how “rpath” and “runpath” affect the building and linking of Open MPI itself.

  When either of “runpath” or “rpath” behaviors are enabled, the applications will have the filesystem path location of the Open MPI libraries hard-coded into the Open MPI/OpenSHMEM application. The most notable differences between “runpath” and “rpath” behavior are:

  - runpath

    > 1. The run-time linker first searches the paths in the `LD_LIBRARY_PATH` environment variable for the relevant Open MPI/OpenSHMEM libraries.

    > 2. If not found there, the run-time linker falls back to checking the hard-coded location for the relevant Open MPI/OpenSHMEM libraries.

  - rpath

    > 1. The run-time linker first checks the hard-coded location for the relevant Open MPI/OpenSHMEM libraries.

    > 2. If not found there, the run-time linker falls back to searching the paths in the `LD_LIBRARY_PATH` environment variable for the relevant Open MPI/OpenSHMEM libraries.

  Warning

  There are other, subtle differences between “runpath” and “rpath” which are out of scope for this documentation. You may wish to consult other sources for more information.

  For example, a decent set of explanations can be found in the slides for a Linux course entitled “Building and Using Shared Libraries on Linux // Shared Libraries: The Dynamic Linker”.

  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 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, since the runtime will search the paths in `LD_LIBRARY_PATH` first.

  In the rpath case, since the run-time linker searches the `/opt/openmpi/A.B.0` location that is hard-coded in your MPI application first, your application will use the libraries from your A.B.0 installation (regardless of the value of the `LD_LIBRARY_PATH` environment variable).

  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.

  As noted above, both runpath/rpath behaviors can be disabled via `--disable-wrapper-rpath`.

  Note

  You can also customize the compiler/linker flags that are used by the wrapper compilers to build Open MPI/OpenSHMEM applications.

- `--enable-dlopen`: Enable Open MPI to load components as standalone Dynamic Shared Objects (DSOs) at run-time. This option is enabled by default.

  The opposite of this option, `--disable-dlopen`, causes the following:

  1. Open MPI will not attempt to open any DSOs at run-time.

  2. configure behaves as if the `--enable-mca-static` argument was set.

  3. configure will ignore the `--enable-mca-dso` argument.

  See the description of `--enable-mca-static` / `--enable-mca-dso` for more information.

  Note

  This option does not change how Open MPI’s libraries (`libmpi`, for example) will be built. You can change whether Open MPI builds static or dynamic libraries via the `--enable|disable-static` and `--enable|disable-shared` arguments.

- `--enable-mca-dso[=LIST]` and `--enable-mca-static[=LIST]` These two options, along with `--enable-mca-no-build`, govern the behavior of how Open MPI’s frameworks and components are built.

  Tip

  See this section for advice to packagers about these CLI options.

  The `--enable-mca-dso` option specifies which frameworks and/or components are built as Dynamic Shared Objects (DSOs). Specifically, DSOs are built as “plugins” outside of the core Open MPI libraries, and are loaded by Open MPI at run time.

  The `--enable-mca-static` option specifies which frameworks and/or components are built as part of the core Open MPI libraries (i.e., they are not built as DSOs, and therefore do not need to be separately discovered and opened at run time).

  Both options can be used one of two ways:

  1. `--enable-mca-OPTION` (with no value)

  2. `--enable-mca-OPTION=LIST`

  `--enable-mca-OPTION=no` or `--disable-mca-OPTION` are both legal options, but have no impact on the selection logic described below. Only affirmative options change the selection process.

  If `LIST` is not specified (e.g., `--enable-mca-dso` with no `LIST`), or if `LIST` is the special value `yes`, then all components will be selected. If `LIST` is specified, it is a comma-delimited list of Open MPI frameworks and/or framework+component tuples. Examples:

  - `btl` specifies the entire BTL framework

  - `btl-tcp` specifies just the TCP component in the BTL framework

  - `mtl,btl-tcp` specifies the entire MTL framework and the TCP component in the BTL framework

  Open MPI’s `configure` script uses the values of these two options when evaluating each component to determine how it should be built by evaluating these conditions in order:

  1. If an individual component’s build behavior has been specified via these two options, `configure` uses that behavior.

  2. Otherwise, if the component is in a framework whose build behavior has been specified via these two options, `configure` uses that behavior.

  3. Otherwise, `configure` uses the global default build behavior.

  At each level of the selection process, if the component is specified to be built as both a static and DSO component, the static option will win.

  Note

  As of Open MPI v5.0.1, `configure`’s global default is to build all components as static (i.e., part of the Open MPI core libraries, not as DSOs). Prior to Open MPI v5.0.0, the global default behavior was to build most components as DSOs.

  Important

  If the `--disable-dlopen` option is specified, then Open MPI will not be able to search for DSOs at run time, and the value of the `--enable-mca-dso` option will be silently ignored.

  Some examples:

  1. Default to building all components as static (i.e., as part of the Open MPI core libraries — no DSOs):

         shell$ ./configure

  2. Build all components as DSOs:

         shell$ ./configure --enable-mca-dso

  3. Build all components as static, except the TCP BTL, which will be built as a DSO:

         shell$ ./configure --enable-mca-dso=btl-tcp

  4. Build all components as static, except all BTL components, which will be built as DSOs:

         shell$ ./configure --enable-mca-dso=btl

  5. Build all components as static, except all MTL components and the TCP BTL component, which will be built as DSOs:

         shell$ ./configure --enable-mca-dso=mtl,btl-tcp

  6. Build all BTLs as static, except the TCP BTL, as the `<framework-component>` option is more specific than the `<framework>` option:

         shell$ ./configure --enable-mca-dso=btl --enable-mca-static=btl-tcp

  7. Build the TCP BTL as static, because the static option at the same level always wins:

         shell$ ./configure --enable-mca-dso=btl-tcp --enable-mca-static=btl-tcp

- `--enable-mca-no-build=LIST`: Comma-separated list of `<framework>-<component>` pairs that will not be built. For example, `--enable-mca-no-build=threads-qthreads,pml-monitoring` will disable building both the `qthreads` threading component and the `monitoring` PML.

  Note

  This option is typically only useful for components that would otherwise be built. For example, if you are on a machine without Libfabric support, it is not necessary to specify:

      shell$ ./configure --enable-mca-no-build=cm-ofi

  because the `configure` script will naturally see that you do not have support for Libfabric and will automatically skip the `ofi` CM component.

- `--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.