gpaulsen/ompi-release

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===========================================================================

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===========================================================================

Much, much more information is also available in the Open MPI FAQ:

http://www.open-mpi.org/faq/

===========================================================================

The following abbreviated list of release notes applies to this code
base as of this writing (April 2015):

General notes

• 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 "OSHMEM" 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 is provided on an experimental basis;
  it has been lightly tested and will only work in Linux environments.
  Although this implementation attempts to be portable to multiple
  different environments and networks, it is still new and will likely
  experience growing pains typical of any new software package.
  End-user feedback is greatly appreciated.

  This implementation will currently most likely provide optimal
  performance on Mellanox hardware and software stacks. Overall
  performance is expected to improve as other network vendors and/or
  institutions contribute platform specific optimizations.

• 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 -- Myrinet, 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
  (http://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
  • LoadLeveler
  • PBS Pro, Torque
  • Platform LSF (v7.0.2 and later)
  • SLURM
  • Cray XE 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), 32 bit, with gcc
  • Linux (various flavors/distros), 64 bit (x86), with gcc, Absoft,
    Intel, and Portland (*)
  • OS X (10.6, 10.7, 10.8, 10.9, 10.10), 32 and 64 bit (x86_64), with
    XCode and Absoft compilers (*)

  (*) Be sure to read the Compiler Notes, below.

• Other systems have been lightly (but not fully tested):

  • Cygwin 32 & 64 bit with gcc
  • ARMv4, ARMv5, ARMv6, ARMv7, ARMv8
  • Other 64 bit platforms (e.g., Linux on PPC64)
  • Oracle Solaris 10 and 11, 32 and 64 bit (SPARC, i386, x86_64),
    with Oracle Solaris Studio 12.2, 12.3, and 12.4

Compiler Notes

• Open MPI requires a C99-capable compiler to build.

• 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.

• 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 GOOD (and 12.8 and 12.9 both known BAD with
  --enable-debug)
  pgi-13: 13.10 known GOOD

• 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).

• IBM's xlf compilers: NO known good version that can build/link
  the MPI f08 bindings or build/link the OSHMEM Fortran bindings.

• 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.

• 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 new 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.

• It has been noticed that if one uses CXX=sunCC, in which sunCC
  is a link in the Solaris Studio compiler release, that the OMPI
  build system has issue with sunCC and does not build libmpi_cxx.so.
  Therefore the make install fails. So we suggest that one should
  use CXX=CC, which works, instead of CXX=sunCC.

• 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.

• The Solaris Studio 12.2 compilers may have a problem compiling
  VampirTrace on some Linux platforms. You can either upgrade to a
  later version of the Solaris Studio compilers (e.g., 12.3 does not
  have this problem), or disable building VampirTrace.

• 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.

• The Intel 9.0 v20051201 compiler on IA64 platforms seems to have a
  problem with optimizing the ptmalloc2 memory manager component (the
  generated code will segv). As such, the ptmalloc2 component will
  automatically disable itself if it detects that it is on this
  platform/compiler combination. The only effect that this should
  have is that the MCA parameter mpi_leave_pinned will be inoperative.

• 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.

• Early versions of the Portland Group 6.0 compiler have problems
  creating the C++ MPI bindings as a shared library (e.g., v6.0-1).
  Tests with later versions show that this has been fixed (e.g.,
  v6.0-5).

• 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.

• Using the MPI C++ bindings with older versions of the Pathscale
  compiler on some platforms is an old issue that seems to be a
  problem when Pathscale uses a back-end GCC 3.x compiler. Here's a
  proposed solution from the Pathscale support team (from July 2010):

  The proposed work-around is to install gcc-4.x on the system and
  use the pathCC -gnu4 option. Newer versions of the compiler (4.x
  and beyond) should have this fixed, but we'll have to test to
  confirm it's actually fixed and working correctly.
  

  We don't anticipate that this will be much of a problem for Open MPI
  users these days (our informal testing shows that not many users are
  still using GCC 3.x). Contact Pathscale support if you continue to
  have problems with Open MPI's C++ bindings.

• 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 OSHMEM 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):

  • 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.

  • mpi module: The mpi module file was added in MPI-2. It provides
    strong compile-time parameter type checking for MPI subroutines.

  • 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.

    *** The mpi_f08 module is STRONGLY is 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 OSHMEM specification, there is only one Fortran OSHMEM binding
  provided:

  • shmem.fh: All Fortran OpenSHMEM programs should include 'shmem.fh',
    and Fortran OSHMEM 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 support 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 is new and has been tested with the Intel
    Fortran compiler and gfortran >= v4.9. Other modern Fortran
    compilers may also work (but are, as yet, only lightly tested).
    It is expected that this support will mature over time.

    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 MCA ("MPI
  Component Architecture") 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" paramater 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 functionality is supported.

• 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 support is included, but is only lightly tested.
  It likely does not work for thread-intensive applications. Note
  that only the MPI point-to-point communication functions for the
  BTL's listed here are considered thread safe. Other support
  functions (e.g., MPI attributes) have not been certified as safe
  when simultaneously used by multiple threads.

  • tcp
  • sm
  • self

  Note that Open MPI's thread support is in a fairly early stage; the
  above devices may work, but the latency is likely to be fairly
  high. Specifically, efforts so far have concentrated on
  correctness, not performance (yet).

  YMMV.

• 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 appliation 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. Patches and/or suggestions
  would be greatfully appreciated on the Open MPI developer's list.

OSHMEM Functionality and Features

• All OpenSHMEM-1.0 functionality is supported.

MPI Collectives

• The "hierarch" coll component (i.e., an implementation of MPI
  collective operations) attempts to discover network layers of
  latency in order to segregate individual "local" and "global"
  operations as part of the overall collective operation. In this
  way, network traffic can be reduced -- or possibly even minimized
  (similar to MagPIe). The current "hierarch" component only
  separates MPI processes into on- and off-node groups.

  Hierarch has had sufficient correctness testing, but has not
  received much performance tuning. As such, hierarch is not
  activated by default -- it must be enabled manually by setting its
  priority level to 100:

  mpirun --mca coll_hierarch_priority 100 ...

  We would appreciate feedback from the user community about how well
  hierarch works for your applications.

• The "fca" coll 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 "ML" coll component is an implementation of MPI collective
  operations that takes advantage of communication hierarchies
  in modern systems. A ML collective operation is implemented by
  combining multiple independently progressing collective primitives
  implemented over different communication hierarchies, hence a ML
  collective operation is also referred to as a hierarchical collective
  operation. The number of collective primitives that are included in a
  ML collective operation is a function of subgroups(hierarchies).
  Typically, MPI processes in a single communication hierarchy such as
  CPU socket, node, or subnet are grouped together into a single subgroup
  (hierarchy). The number of subgroups are configurable at runtime,
  and each different collective operation could be configured to have
  a different of number of subgroups.

  The component frameworks and components used by/required for a
  "ML" collective operation.

  Frameworks:

  • "sbgp" - Provides functionality for grouping processes into subgroups
  • "bcol" - Provides collective primitives optimized for a particular
    communication hierarchy

  Components:

  • sbgp components - Provides grouping functionality over a CPU socket
    ("basesocket"), shared memory ("basesmuma"),
    Mellanox's ConnectX HCA ("ibnet"), and other
    interconnects supported by PML ("p2p")

  • BCOL components - Provides optimized collective primitives for
    shared memory ("basesmuma"), Mellanox's ConnectX
    HCA ("iboffload"), and other interconnects supported
    by PML ("ptpcoll")

• 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.

OSHMEM 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 OSHMEM
  collective operations.

Network Support

• There are two MPI network models available: "ob1", and "cm". "ob1"
  uses BTL ("Byte Transfer Layer") components for each supported network.
  "cm" uses MTL ("Matching Tranport Layer") components for each supported
  network.

  • "ob1" supports a variety of networks that can be used in
    combination with each other (per OS constraints; e.g., there are
    reports that the GM and OpenFabrics kernel drivers do not operate
    well together):

    • OpenFabrics: InfiniBand, iWARP, and RoCE
    • Loopback (send-to-self)
    • Shared memory
    • TCP
    • Intel Phi SCIF
    • SMCUDA
    • Cisco usNIC
    • uGNI (Cray Gemini, Aries)
    • vader (XPMEM, Linux CMA, Linux KNEM, and general shared memory)

  • "cm" supports a smaller number of networks (and they cannot be
    used together), but may provide better overall MPI performance:

    • QLogic InfiniPath / Intel True Scale PSM
    • Intel Omni-Path PSM2
    • Mellanox MXM
    • Portals4
    • OpenFabrics Interfaces ("libfabric" tag matching)

    Open MPI will, by default, choose to use "cm" when one of the
    above transports can be used. Otherwise, "ob1" will be used and
    the corresponding BTLs will be selected. Users can force the use
    of ob1 or cm if desired by setting the "pml" MCA parameter at
    run-time:

    shell$ mpirun --mca pml ob1 ...
    or
    shell$ mpirun --mca pml cm ...

• Similarly, there are two OSHMEM network models available: "yoda",
  and "ikrit". "yoda" also uses the BTL components for many supported
  network. "ikrit" interfaces directly with Mellanox MXM.

  • "yoda" supports a variety of networks that can be used:

    • OpenFabrics: InfiniBand, iWARP, and RoCE
    • Loopback (send-to-self)
    • Shared memory
    • TCP

  • "ikrit" only supports Mellanox MXM.

• MXM is the Mellanox Messaging Accelerator library utilizing a full
  range of IB transports to provide the following messaging services
  to the upper level MPI/OSHMEM libraries:

  • Usage of all available IB transports
  • Native RDMA support
  • Progress thread
  • Shared memory communication
  • Hardware-assisted reliability

• 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 the Cisco usNIC device.

• 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
  OFED v1.1 (and later).

• Better memory management support is available for OFED-based
  transports using the "ummunotify" Linux kernel module. OFED memory
  managers are necessary for better bandwidth when re-using the same
  buffers for large messages (e.g., benchmarks and some applications).

  Unfortunately, the ummunotify module was not accepted by the Linux
  kernel community (and is still not distributed by OFED). But it
  still remains the best memory management solution for MPI
  applications that used the OFED network transports. If Open MPI is
  able to find the <linux/ummunotify.h> header file, it will build
  support for ummunotify and include it by default. If MPI processes
  then find the ummunotify kernel module loaded and active, then their
  memory managers (which have been shown to be problematic in some
  cases) will be disabled and ummunotify will be used. Otherwise, the
  same memory managers from prior versions of Open MPI will be used.
  The ummunotify Linux kernel module can be downloaded from:

  http://lwn.net/Articles/343351/

• The use of fork() with OpenFabrics-based networks (i.e., the openib
  BTL) 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.

• Support for Myrinet MX has been removed. Please use a prior version of Open
  MPI if you need the MX support.

• Linux "knem" support is used when the "vader" or "sm" (shared
  memory) BTLs are 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 http://runtime.bordeaux.inria.fr/knem/ for details on Knem.

• Linux Cross-Memory Attach (CMA) or XPMEM is used by the vader
  shared-memory BTL when the CMA/XPMEM libraries are installedm,
  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 has been added (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:

  • affinity: Provides the OMPI_Affinity_str() routine on retrieving
    a string that contains what resources a process is bound to. See
    its man page for more details.
  • cr: Provides routines to access to checkpoint restart routines.
    See ompi/mpiext/cr/mpiext_cr_c.h for a listing of availble
    functions.
  • example: A non-functional extension; its only purpose is to
    provide an example for how to create other extensions.

===========================================================================

Building Open MPI

Open MPI uses a traditional configure script paired with "make" to
build. Typical installs can be of the pattern:

---

shell$ ./configure [...options...]
shell$ make all install

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 that for many of Open MPI's --with- options, Open MPI will,
by default, search for header files and/or libraries for . If
the relevant files are found, Open MPI will built support for ;
if they are not found, Open MPI will skip building support for .
However, if you specify --with- on the configure command line and
Open MPI is unable to find relevant support for , 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.

INSTALLATION OPTIONS

--prefix=
Install Open MPI into the base directory named . Hence,
Open MPI will place its executables in /bin, its header
files in /include, its libraries in /lib, etc.

--disable-shared
By default, libmpi and libshmem are built as a shared library, 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 libmpi and libshmem 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:

"rpath": the location of the Open MPI libraries is hard-coded into
the MPI/OSHMEM application and cannot be overridden at run-time.
"runpath": the location of the Open MPI libraries is hard-coded into
the MPI/OSHMEM 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/OSHMEM 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.

--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).
2. 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.

--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.

NETWORKING SUPPORT / OPTIONS

--with-fca=
Specify the directory where the Mellanox FCA library and
header files are located.

FCA is the support library for Mellanox QDR switches and HCAs.

--with-hcoll=
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=
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 http://runtime.bordeaux.inria.fr/knem/ for
details.

--with-libfabric=
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, etc.

--with-libfabric-libdir=
Look in directory for the libfabric libraries. By default, Open MPI
will look in /lib and /lib64, which covers most cases. This option is only
needed for special configurations.

--with-mxm=
Specify the directory where the Mellanox MXM library and header
files are located. This option is generally only necessary if the
MXM headers and libraries are not in default compiler/linker search
paths.

MXM is the support library for Mellanox Network adapters.

--with-mxm-libdir=
Look in directory for the MXM libraries. By default, Open MPI will
look in /lib and /lib64, which covers
most cases. This option is only needed for special configurations.

--with-openib=
DEPRECATED synonym for --with-verbs.

--with-openib-libdir=
DEPRECATED synonym for --with-verbs-libdir.

--with-portals4=
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=
Location of libraries to link with for Portals4 support.

--with-portals4-max-md-size=SIZE
--with-portals4-max-va-size=SIZE
Set configuration values for Portals 4

--with-psm=
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=
Look in directory for the PSM libraries. By default, Open MPI will
look in /lib and /lib64, which covers
most cases. This option is only needed for special configurations.

--with-psm2=
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.

PSM2 is the support library for Intel Omni-Path network adapters.

--with-psm2-libdir=
Look in directory for the PSM2 libraries. By default, Open MPI will
look in /lib and /lib64, which
covers most cases. This option is only needed for special
configurations.

--with-scif=

Look in directory for Intel SCIF support libraries

--with-usnic
Abort configure if Cisco usNIC support cannot be built.

--with-verbs=
Specify the directory where the verbs (also know as OpenFabrics, and
previously known as OpenIB) libraries and header files are located.
This option is generally only necessary if the verbs headers and
libraries are not in default compiler/linker search paths.

"OpenFabrics" refers to operating system bypass networks, such as
InfiniBand, usNIC, iWARP, and RoCE (aka "IBoIP").

--with-verbs-libdir=
Look in directory for the verbs libraries. By default, Open
MPI will look in /lib and /lib64, which covers most cases. This option is only
needed for special configurations.

--with-verbs-usnic
This option will activate support in Open MPI for disabling a
dire-sounding warning message from libibverbs that Cisco usNIC
devices are not supported (because Cisco usNIC devices are supported
through libfabric, not libibverbs). This libibverbs warning can
also be suppressed by installing the "no op" libusnic_verbs plugin
for libibverbs (see https://github.com/cisco/libusnic_verbs, or
download binaries from cisco.com). This option is disabled by
default because it causes libopen-pal.so to depend on libibverbs.so,
which is undesirable to many downstream packagers.

--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-orterun-prefix-by-default is a synonym for
this option.

--enable-sensors
Enable internal sensors (default: disabled).

--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-cray-pmi-ext
Include Cray PMI2 extensions.

--with-loadleveler
Force the building of LoadLeveler scheduler support. If LoadLeveler
support cannot be found, configure will abort.

--with-lsf=
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.

NOTE: If you are using LSF version 7.0.5, you will need to add
"LIBS=-ldl" to the configure command line. For example:

        ./configure LIBS=-ldl --with-lsf ...

    This workaround should *only* be needed for LSF 7.0.5.

--with-lsf-libdir=
Look in directory for the LSF libraries. By default, Open MPI will
look in /lib and /lib64, which covers
most cases. This option is only needed for special configurations.

--with-pmi
Build PMI support (by default, it is not built). If the pmi2.h
header is found in addition to pmi.h, then support for PMI2 will be
built.

--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.

--with-tm=
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-blcr=
Specify the directory where the Berkeley Labs Checkpoint / Restart
(BLCR) libraries and header files are located. This option is
generally only necessary if the BLCR headers and libraries are not
in default compiler/linker search paths.

This option is only meaningful if the --with-ft option is also used
to active Open MPI's fault tolerance behavior.

--with-blcr-libdir=
Look in directory for the BLCR libraries. By default, Open MPI will
look in /lib and /lib64, which
covers most cases. This option is only needed for special
configurations.

--with-dmtcp=
Specify the directory where the Distributed MultiThreaded
Checkpointing (DMTCP) libraries and header files are located. This
option is generally only necessary if the DMTCP headers and
libraries are not in default compiler/linker search paths.

This option is only meaningful if the --with-ft option is also used
to active Open MPI's fault tolerance behavior.

--with-dmtcp-libdir=
Look in directory for the DMTCP libraries. By default, Open MPI
will look in /lib and /lib64,
which covers most cases. This option is only needed for special
configurations.

--with-libevent(=value)
This option specifies where to find the libevent support headers and
library. The following VALUEs 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".
<directory>: 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 libeveny 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=
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)
Build hwloc support (default: enabled). This option specifies where
to find the hwloc support headers and library. The following values
are permitted:

internal:    Use Open MPI's internal copy of hwloc.
external:    Use an external hwloc installation (rely on default
             compiler and linker paths to find it)
<no value>:  Same as "internal".
<directory>: Specify the location of a specific hwloc
             installation to use

By default (or if --with-hwloc is specified with no VALUE), Open MPI
will build and use the copy of hwloc that it has in its source tree.
However, if the VALUE is "external", Open MPI will look for the
relevant hwloc header files and library in default compiler / linker
locations. Or, VALUE can be a directory tree where the hwloc header
file and library can be found. This option allows operating systems
to include Open MPI and use their default hwloc installation instead
of Open MPI's bundled hwloc.

hwloc is a support library that provides processor and memory
affinity information for NUMA platforms.

--with-hwloc-libdir=
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=
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(=)
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.

--disable-vt
Disable building the VampirTrace that is bundled with Open MPI.

MPI FUNCTIONALITY

--with-mpi-param-check(=value)
Whether or not to check MPI function parameters for errors at
runtime. The following values 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 "none" (same as --without-mpi-param-check).

If --with-mpi-param is not specified, "runtime" is the default.

--with-threads=value
Since thread support is only partially tested, it is disabled by
default. To enable threading, use "--with-threads=posix". This is
most useful when combined with --enable-mpi-thread-multiple.

--enable-mpi-thread-multiple
Allows the MPI thread level MPI_THREAD_MULTIPLE. See
--with-threads; this is currently disabled by default. Enabling
this feature will automatically --enable-opal-multi-threads.

--enable-mpi-cxx
Enable building the C++ MPI bindings (default: disabled).

The MPI C++ bindings were deprecated in MPI-2.2, and removed from
the MPI standard in MPI-3.0.

--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
values 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:      Build mpif.h support.
usempi:     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 OSHMEM Fortran interface.

--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.txt
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.txt for more details.

--enable-mpi-ext(=)
Enable Open MPI's non-portable API extensions. If no is
specified, all of the extensions are enabled.

See "Open MPI API Extensions", below, for more details.

--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.

--enable-sparse-groups
Enable the usage of sparse groups. This would save memory
significantly especially if you are creating large
communicators. (Disabled by default)

OSHMEM FUNCTIONALITY

--disable-oshmem
Disable building the OpenSHMEM implementation (by default, it is
enabled).

--disable-oshmem-fortran
Disable building only the Fortran OSHMEM 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=
--with-wrapper-cxxflags=
--with-wrapper-fflags=
--with-wrapper-fcflags=
--with-wrapper-ldflags=
--with-wrapper-libs=
Add the specified flags to the default flags that used are 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:

: Flags passed by the mpicc wrapper to the C compiler
: Flags passed by the mpic++ wrapper to the C++ compiler
: Flags passed by the mpifort wrapper to the Fortran compiler
: Flags passed by all the wrappers to the linker
: 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 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 FC, 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 /bin is in their PATH and /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:

• Software version number
• 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-release/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/OSHMEM 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 / OSHMEM run time system
• mpirun / oshrun command line options
• MCA parameter names / values / meanings

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 compatibile 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).

• Quantifier: Open MPI version numbers sometimes have an arbitrary
  string affixed to the end of the version number. Common strings
  include:

  o 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).
  o 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).
  o 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 most recent Git tag name on the branch from which the tarball
  was created.
• An integer indicating how many Git commits have occurred since
  that Git tag.
• The Git hash of the tip of the branch.

For example, a snapshot tarball filename of
"openmpi-v1.8.2-57-gb9f1fd9.tar.bz2" indicates that this tarball was
created from the v1.8 branch, 57 Git commits after the "v1.8.2" tag,
specifically at Git hash gb9f1fd9.

Open MPI's Git master branch contains a single "dev" tag. For
example, "openmpi-dev-8-gf21c349.tar.bz2" represents a snapshot
tarball created from the master branch, 8 Git commits after the "dev"
tag, specifically at Git hash gf21c349.

The exact value of the "number of Git commits past a tag" integer is
fairly meaningless; its sole purpose is to provide an easy,
human-recognizable ordering for snapshot tarballs.

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.

2. 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.

3. If the library source code has changed at all since the last
   update, then increment revision ("c:r:a" becomes "c:r+1:a").

4. If any interfaces have been added, removed, or changed since the
   last update, increment current, and set revision to 0.

5. If any interfaces have been added since the last public release,
   then increment age.

6. 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.

2. 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_*

3. 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/OSHMEM interfaces; we therefore want
   the .so version number to reflect only changes to the official
   MPI/OSHMEM APIs. Put simply: non-MPI/OSHMEM API / internal
   changes to the MPI-application-facing libraries are irrelevant to
   pure MPI/OSHMEM applications.

   • libmpi
   • libmpi_mpifh
   • libmpi_usempi_tkr
   • libmpi_usempi_ignore_tkr
   • libmpi_usempif08
   • libmpi_cxx
   • libmpi_java
   • liboshmem
   • liboshmem_java

===========================================================================

Checking Your Open MPI Installation

The "ompi_info" command can be used to check the status of your Open
MPI installation (located in /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
A of "all" and a 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 and/or
name.
--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 (the max
value is 9). Use "ompi_info --param
--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.

2. 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).

3. 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).

4. Use "oshrun" to launch a non-OSHMEM program across multiple nodes.

5. Use "oshrun" to launch a trivial MPI program that does no OSHMEM
   communication (e.g., hello_shmem.c program in the examples/ directory
   in the Open MPI distribution.)

6. Use "oshrun" to launch a trivial OSHMEM 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 not enabled by default; they must be enabled
by Open MPI's configure script. The --enable-mpi-ext command line
switch accepts a comma-delimited list of extensions to enable, or, if
it is specified without a list, all extensions are enabled.

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:

---

#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 OSHMEM 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 OSHMEM 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 or 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.

orte: Open MPI Run-Time Environment applicaions
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. Some of mpiexec's switches (such as -host and -arch)
are not yet functional, although they will not error if you try to use
them.

The rsh launcher (which defaults to using ssh) accepts a -hostfile
parameter (the option "-machinefile" is equivalent); you can specify a
-hostfile parameter indicating an 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:

---

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 OSHMEM applications. For example:

shell$ oshrun -np 2 hello_world_oshmem

OSHMEM applications may also be launched directly by resource managers
such as SLURM. For example, when OMPI is configured --with-pmi and
--with-slurm one may launch OSHMEM 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. Here is a list of all the
component frameworks in Open MPI:

---

MPI component frameworks:

allocator - Memory allocator
bcol - Base collective operations
bml - BTL management layer
btl - MPI point-to-point Byte Transfer Layer, used for MPI
point-to-point messages on some types of networks
coll - MPI collective algorithms
crcp - Checkpoint/restart coordination protocol
dpm - MPI dynamic process management
fbtl - file byte transfer layer: abstraction for individual
read/write operations for OMPIO
fcoll - collective read and write operations for MPI I/O
fs - file system functions for MPI I/O
io - MPI I/O
mpool - Memory pooling
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
pubsub - MPI publish/subscribe management
rcache - Memory registration cache
rte - Run-time environment operations
sbgp - Collective operation sub-group
sharedfp - shared file pointer operations for MPI I/O
topo - MPI topology routines
vprotocol - Protocols for the "v" PML

OSHMEM component frameworks:

atomic - OSHMEM atomic operations
memheap - OSHMEM memory allocators that support the
PGAS memory model
scoll - OSHMEM collective operations
spml - OSHMEM "pml-like" layer: supports one-sided,
point-to-point operations
sshmem - OSHMEM shared memory backing facility

Back-end run-time environment (RTE) component frameworks:

dfs - Distributed file system
errmgr - RTE error manager
ess - RTE environment-specfic services
filem - Remote file management
grpcomm - RTE group communications
iof - I/O forwarding
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
sensor - Software and hardware health monitoring
snapc - Snapshot coordination
sstore - Distributed scalable storage
state - RTE state machine

Miscellaneous frameworks:

backtrace - Debugging call stack backtrace support
compress - Compression algorithms
crs - Checkpoint and restart service
db - Internal database support
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 - Memopy copy support
memory - Memory management hooks
pstat - Process status
shmem - Shared memory support (NOT related to OSHMEM)
timer - High-resolution timers

---

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 openib btl
sends messages across OpenFabrics-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 a some of parameters (and default values) for the tcp btl
component.

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

2. End user / detailed

3. End user / all

4. Application tuner / basic

5. Application tuner / detailed

6. Application tuner / all

7. MPI/OSHMEM developer / basic

8. MPI/OSHMEM developer / detailed

9. MPI/OSHMEM 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/OSHMEM application to run correctly.
2. Application tuner: Generally, these are parameters that can be
   used to tweak MPI application performance.
3. MPI/OSHMEM 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.
2. Detailed: Parameters that are useful, but you probably won't need
   to change them often.
3. 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. /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.

2. $HOME/.openmpi/mca-params.conf

   If this file exists, it should be in the same format as
   /etc/openmpi-mca-params.conf. It is intended to provide
   per-user default parameter values.

3. environment variables of the form OMPI_MCA_ set equal to a
   

   Where 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

   Where 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 relavant. For
example, 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

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.

===========================================================================

Common Questions

Many common questions about building and using Open MPI are answered
on the FAQ:

http://www.open-mpi.org/faq/

===========================================================================

Got more questions?

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. This web page details all the
information that we request in order to provide assistance:

 http://www.open-mpi.org/community/help/

User-level questions and comments should generally be sent to the
user's mailing list (users@open-mpi.org). Because of spam, only
subscribers are allowed to post to this list (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 this page to subscribe to the
user's list:

 http://www.open-mpi.org/mailman/listinfo.cgi/users

Developer-level bug reports, questions, and comments should generally
be sent to the developer's mailing list (devel@open-mpi.org). Please
do not post the same question to both lists. As with the user's list,
only subscribers are allowed to post to the developer's list. Visit
the following web page to subscribe:

 http://www.open-mpi.org/mailman/listinfo.cgi/devel

Make today an Open MPI day!