11.1. Supported systems


11.1.1. What operating systems does Open MPI support?

We primarily develop Open MPI on Linux and MacOS.

Other operating systems are supported, however. The exact list of operating systems supported has changed over time (e.g., native Microsoft Windows support was added in v1.3.3, and although it was removed prior to v1.8, is still supported through Cygwin). See the Platform Notes section for a listing of the OSes that that version supports.

Open MPI is fairly POSIX-neutral, so it will run without too many modifications on most POSIX-like systems. Hence, if we haven’t listed your favorite operating system here, it may not be difficult to get Open MPI to compile and run properly. The biggest obstacle is typically the assembly language, but that’s fairly modular and we’re happy to provide information about how to port it to new platforms.

It should be noted that we are quite open to accepting patches for operating systems that we do not currently support. If we do not have systems to test these on, we probably will only claim to “unofficially” support those systems.


11.1.2. What hardware platforms does Open MPI support?

Essentially all the common platforms that the operating systems listed in the previous question support.

For example, Linux runs on a wide variety of platforms, and we certainly don’t claim to test all of them. Open MPI includes Linux-compiler-based assembly for support of Intel, AMD, ARM, and PowerPC chips, for example.


11.1.3. What network interconnects does Open MPI support?

See the Platform Notes section for a list of networks supported in this specific release of Open MPI.

The set of commonly-available HPC-class network interconnects has evolved and changed over time.

Reflecting that evolution, each release of Open MPI supports a specific set of such network interconnects. You will need to check the documentation of the version of your Open MPI installation to see which interconnects it supports. A general rule of thumb is that a given Open MPI version tends to support the popular HPC-class interconnects at the time of its release.

This, unfortunately, does mean that Open MPI removes support for networks that are no longer commonly-used in HPC environments. If you still have one of these older interconnects, not all new version of Open MPI may support your interconnect – sorry! This simply reflects the reality of limited development, testing, and maintenance resources.

That being said, contributions are always welcome!.


11.1.4. How does Open MPI interface to back-end run-time systems?

Prior versions of Open MPI used to be layered on top of the Open Run-Time Environment (ORTE). ORTE originally started as a small portion of the Open MPI code base, but over time, ORTE effectively spun off into its own sub-project. ORTE ultimately evolved into the Process Management Interface Exascale (PMIx) standard and corresponding OpenPMIx software project.

The OpenPMIx project then evolved its own PMIx Reference Run-Time Environment (PRRTE) project.

PRRTE has effectively replaced ORTE in the Open MPI implementation.


11.1.5. What run-time environments does Open MPI support?

See the Platform Notes section for a list of run-time environments supported in this specific release of Open MPI.

Since Open MPI uses PRRTE as its back-end run-time system, Open MPI supports whatever run-time systems PRRTE supports.

Each version of Open MPI supports a specific set of versions of PRRTE. Those versions therefore determine which run-time systems that that release of Open MPI supports.


11.1.6. How much MPI does Open MPI support?

  • Open MPI 1.2 supports all of MPI-2.0.

  • Open MPI 1.3 supports all of MPI-2.1.

  • Open MPI 1.8 supports all of MPI-3.0.

  • Starting with v2.0, Open MPI supports all of MPI-3.1.


11.1.7. Is Open MPI thread safe?

Support for MPI_THREAD_MULTIPLE (i.e., multiple threads executing within the MPI library) and asynchronous message passing progress (i.e., continuing message passing operations even while no user threads are in the MPI library) has been designed into Open MPI from its first planning meetings.

Support for MPI_THREAD_MULTIPLE was included in the first version of Open MPI, but it only became robust around v3.0.0. Subsequent releases continually improve reliability and performance of multi-threaded MPI applications.


11.1.8. Does Open MPI support 32 bit environments?

As far as we know, yes. 64 bit architectures have effectively taken over the world, though, so 32-bit is not tested nearly as much as 64-bit.

Specifically, most of the Open MPI developers only have 64-bit machines, and therefore only test 32-bit in emulation mode.


11.1.9. Does Open MPI support 64 bit environments?

Yes, Open MPI is 64 bit clean. You should be able to use Open MPI on 64 bit architectures and operating systems with no difficulty.


11.1.10. Does Open MPI support execution in heterogeneous environments?

Heterogeneous support (specifically: supporting different sized and/or represented data types in a single MPI application run) within a single MPI job is technically required by the MPI standard.

However, there are both theoretical and practical problems with supporting true data heterogeneity at run time.

Indeed, it is quite uncommon for production HPC environments to be data-heterogeneous (e.g., natively support little endian on some nodes and big endian on other nodes in the same MPI application job).

As such, supporting data heterogeneity is a feature that has fallen into disrepair: it is currently known to be broken in this release of Open MPI.

Contributions to fix it would be welcome!


11.1.11. Does Open MPI support parallel debuggers?

Yes. Open MPI supports the TotalView API for parallel process attaching, which several parallel debuggers support (e.g., DDT, fx2). As part of v1.2.4 (released in September 2007), Open MPI also supports the TotalView API for viewing message queues in running MPI processes.

See this FAQ entry for details on how to run Open MPI jobs under TotalView, and this FAQ entry for details on how to run Open MPI jobs under DDT.

Note

The integration of Open MPI message queue support is problematic with 64 bit versions of TotalView prior to v8.3:

  • The message queues views will be truncated.

  • Both the communicators and requests list will be incomplete.

  • Both the communicators and requests list may be filled with wrong values (such as an MPI_Send to the destination MPI_ANY_SOURCE).

There are two workarounds:

  • Use a 32 bit version of TotalView

  • Upgrade to TotalView v8.3