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PnMPI Tool Infrastructure

Travis Codecov

by Martin Schulz,, LLNL-CODE-402774

PnMPI is a dynamic MPI tool infrastructure that builds on top of the standardized PMPI interface. It allows the user to

  • run multiple PMPI tools concurrently
  • activate PMPI tools without relinking by just changing a configuration file
  • multiplex toolsets during a single run
  • write cooperative PMPI tools

The package contains two main components:

  • The PnMPI core infrastructure
  • Tool modules that can explicitly exploit PnMPI's capabilities

So far, this software has mainly been tested on Linux clusters with RHEL-based OS distributions as well as IBM's BG/P systems. Continuous integration tests run at Ubuntu 12.04 and 14.04, OSX El Capitan and macOS Sierra. Some preliminary experiments have also included SGI Altix systems. Ports to other platforms should be straightforward, but this is not extensively tested. Please file an issue if you run into problems porting PnMPI or if you successfully deployed PnMPI on a new platform.

Many thanks to our contributors.

A) Building PnMPI

PnMPI uses CMake for its build system.

A1) Dependencies

  • CMake (at least version is required).
  • argp is usually included in glibc. However at macOS you have to install it from homebrew as argp-standalone package.
  • binutils and libiberty for the patcher utility (optional)
  • Doxygen for generating the docs and man-pages. (optional)
  • help2man for generating man-pages. (optional)
  • An MPI implementation with header files. So far, PnMPI has been tested with MPICH, OpenMPI and IntelMPI.

In addition, PnMPI uses git submodules for several CMake modules, wrap and adept-utils. While the deploy source tar-ball includes all required submodules, git users need to checkout them with the following command in the root of the cloned repository:

git submodule update --init --recursive

A2) Configure the project

In the simplest case, you can run this in the top-level directory of the PnMPI tree:

cmake -DCMAKE_INSTALL_PREFIX=/path/to/install/destination
make install

This will configure, build, and install PnMPI to the destination specified. PnMPI supports parallel make with the -j parameter. E.g., for using eight build tasks, use:

cmake -DCMAKE_INSTALL_PREFIX=/path/to/install/destination
make -j8
make install

On more complex machines, such as those with filesystems shared among multiple platforms, you will want to separate out your build directories for each platform. CMake makes this easy.

Create a new build directory named according to the platform you are using, cd into it, an run cmake there. For example:

cd <pnmpi>
mkdir x86_64
cd x86_64
cmake -DCMAKE_INSTALL_PREFIX=/path/to/install/destination ..

Here, <pnmpi> is the top-level directory in the PnMPI tree. Note that when you run CMake this way, you need to supply the path to the PnMPI source directory as the last parameter. Here, that's just .. as we are building in a subdirectory of the source directory. Once you run CMake, simply run make and make install as before:

make -j8
make install

The PnMPI build should auto-detect your MPI installation and determine library and header locations. If you want to build with a particular MPI that is NOT the one auto-detected by the build, you can supply your particular MPI compiler as a parameter:

cmake \
  -DCMAKE_INSTALL_PREFIX=/path/to/install/destination \
  -DMPI_C_COMPILER=/path/to/my/mpicc \

See the documentation in FindMPI.cmake for more details on MPI build configuration options.

If you have problems, you may want to build PnMPI in debug mode. You can do this by supplying an additional parameter to cmake, e.g.:

cmake \
  -DCMAKE_INSTALL_PREFIX=/path/to/install/destination \

The extra/build directory contains a few sample invocations of CMake that have been successfully used on LLNL systems.

A3) Configuring with/without Fortran

By default PnMPI is configured to work with C/C++ and Fortran codes. However, on systems where Fortran is not available, the system should auto-detect this and not build the Fortran libraries and test cases. It can also be manually turned off by adding


to the cmake configuration command.

The PnMPI distribution contains test cases for C and Fortran that allow you to test the correct linkage.

A3a) Optional configuration options

If you want to change the default build configuration, you can enable / disable features by adding the following flags to the cmake configuration command.

  • -DBUILD_DOC=ON: Generate the public code documentation and man-pages. PnMPI developers may enable BUILD_DOC_INTERNAL instead for additional PnMPI internal documentation. (requires Doxygen and help2man)
  • -DENABLE_DEBUG=OFF: Disable PnMPI on-demand debug logging. Disable this option only for performance optimization.
  • -DENABLE_MODULES=OFF: Don't build the built-in modules.
  • -DENABLE_TESTING=ON: Build the test cases and enable the test target.
  • -DENABLE_THREAD_SAFETY=OFF: Build PnMPI without thread safety. PnMPI will limit the MPI threading level if this option is enabled, so it still will be thread safe. Disable this option only for performance optimization.
  • -DENABLE_PNMPIZE=OFF: Don't build the PnMPI invocation tool and don't run any tests for it. This option may be required when testing PnMPI at a platform that doesn't support the execvp() syscall.
  • -DENABLE_ADEPT_UTILS=ON: Enable support for adept-utils, to check the module's symbols for their origin. (Not supported with all compilers.)
  • CMake-codecov provides the additional -DENABLE_COVERAGE=ON option to enable code coverage. You can generate coverage reports with the gcov and lcov targets. Read their README for more information.
  • cmake-sanitizers provides additional options to enable sanitizers for all PnMPI targets. E.g. for AddressSanitizer add -DSANITIZE_ADDRESS=ON. Read their README for more information.

A4) Configuring for cross-compiled environments

When configuring PnMPI in cross-compiled environments (such as Blue Gene/Q systems), it is necessary to provide a matching tool chain file. Many toolchain files are included in CMake, additional example files that allow the compilation on certain LC machines can be found in cmakemodules/Platform and cmakemodules/Toolchain.

For example, to configure PnMPI for a BG/Q machine using the GNU compiler suite, add the following to the cmake configuration command:


You may need to modify the toolchain file for your system.

A5) Installed structure

Once you've installed, all your PnMPI files and executables should be in <CMAKE_INSTALL_PREFIX>, the path specified during configuration. Roughly, the install tree looks like this:

  pnmpi                PnMPI invocation tool
  pnmpi-patch          Library patching utility
  libpnmpi[f].[so,a]   PnMPI runtime libraries
  pnmpi-modules/       System-installed tool modules
  cmake/               Build files for external modules
  pnmpi/               PnMPI header directory
    debug_io.h         PnMPI module debug print functions.
    hooks.h            PnMPI module hook definitions.
    service.h          PnMPI module service functions.
  pnmpi.h              PnMPI main header
  pnmpimod.h           PnMPI module support (legacy)
  pnmpi-config.h       CMake generated configuration file
  cmake/               CMake files to support tool module builds

Test programs are not installed, but in the tests/src folder of the build directory, there should also be test programs built with PnMPI. See below for details on running these to test your PnMPI installation.

A6) Environment setup

You will need to set one environment variable to run PnMPI:

  • PNMPI_LIB_PATH should be set to the full path to the PnMPI modules directory. If not set, the default path of your installation directory will be used.
  • PNMPI_CONF should be set to the full to the path of the PnMPI configuration file to be used.
  • PNMPI_BE_SILENT will silence the PnMPI banner. For benchmark purposes you should also disable ENABLE_DEBUG in your CMake configuration. Note: Warnings on errors still will be printed.

A6a) Using the PnMPI invocation tool

To run PnMPI in front of any application (that is dynamically linked to MPI), you may use the bin/pnmpi tool. It will setup the environment and preloads PnMPI for you. For a list of supported arguments, invoke it with the --help flag.

:~$ pnmpi --help
Usage: pnmpi [OPTION...] utility [utility options]
P^nMPI -- Virtualization Layer for the MPI Profiling Interface

  -c, --config=FILE          Configuration file
  -q, -s, --quiet, --silent  Don't produce any output
  -?, --help                 Give this help list
      --usage                Give a short usage message
  -V, --version              Print program version

:~$ mpiexec -np 2 pnmpi -c pnmpi.conf a.out
  _____   _ __   __  __  _____   _____
 |  __ \ | '_ \ |  \/  ||  __ \ |_   _|
 | |__) || | | || \  / || |__) |  | |
 |  ___/ |_| |_|| |\/| ||  ___/   | |
 | |            | |  | || |      _| |_
 |_|            |_|  |_||_|     |_____|

  MPI interface: C

 Global settings:
  Pcontrol: 5

 Loaded modules:
  Stack default:
    sample1 (Pcontrol: 1)
  Stack foo:

Note: The PnMPI invocation tool is not compatible with all platforms (e.g. BlueGene/Q), as it requires the execvp() function, which might not be supported.

A7) RPATH settings

By default, the build adds the paths of all dependency libraries to the rpath of the installed PnMPI library. This is the preferred behavior on LLNL systems, where many packages are installed and LD_LIBRARY_PATH usage can become confusing.

If you are installing on a system where you do NOT want dependent libraries added to your RPATH, e.g. if you expect all of PnMPI's dependencies to be found in system paths, then you can build without rpath additions using this option to cmake:


This will add only the PnMPI installation lib directory to the rpath of the PnMPI library.

B) Usage

PnMPI supports multiple ways to use it with an MPI application:

B1) Dynamic linking

If your application is dynamically linked against the MPI library, you may use PnMPI by simply preloading it via LD_PRELOAD (or DYLD_INSERT_LIBRARIES at macOS).

Instead of manually preloading, you may use the PnMPI invocation tool in bin/pnmpi.

B2) Static linking

Instead of linking your application against the MPI library, you may link against the static MPI library.

Note: By default the linker will only link functions used by your code, so most of the API functions would not get linked into your binary. PnMPI implements a helper function to force the linker to link all required functions into the binary. However there might be complications, if not all functions wrapped by the modules are used by the application. You should tell the linker to link the whole PnMPI archive explicitly:

mpicc main.o -Wl,--whole-archive pnmpi.a -Wl,--no-whole-archive -o test

Note: The linker option --whole-archive is not available at mac OS.

C) Modules

PnMPI supports two different kind of tool modules:

  • Transparent modules
  • PnMPI-specific modules

Among the former are modules that have been created independently of PnMPI and are just based on the PMPI interface. To use a transparent module in PnMPI the user has to perform two steps:

  1. Build the tool as a shared module (a dlopen-able shared library).
  2. Patch the tool using the pnmpi-patch utility, which is included with the PnMPI distribution.


pnmpi-patch <original tool (in)> <patched tool (out)>



After that, copy the tool in one of the directories listed in $PNMPI_LIB_PATH so that PnMPI can pick it up. Note that all of this is handled automatically by the CMake build files included with PnMPI (see below for more information).

The second option is the use of PnMPI specific modules: these modules also rely on the PMPI interface, but explicitly use some of the PnMPI features (i.e., they won't run outside of PnMPI). These modules include the PnMPI header files, which describe the interface that modules can use. In short, the interface offers an ability to register a module and after that use a publish/subscribe interface to offer/use services in other modules.

Note: also PnMPI specific modules have to be patched using the utility described above, if they don't use the XMPI interface instead of the PMPI.

C1) Built-in modules

This package includes a set of modules that can be used both to create other tools using their services and as templates for new modules.

The source for all modules is stored in separate directories inside the src/modules/ directory. There are:

  • sample: A set of example modules that show how to wrap send and receive operations.

  • empty: A transparent module that simply wraps all calls without executing any code. This can be used to test overhead or as a sample for new modules.

  • status: This PnMPI specific module offers a service to add extra data to each status object to store additional information.

  • requests: This PnMPI specific module offers a service to track asynchronous communication requests. It relies on the status module.

  • datatype: This PnMPI specific module tracks all datatype creations and provides an iterator to walk any datatype.

  • comm: This PnMPI specific module abstracts all communication in a few simple callback routines. It can be used to write quick prototype tools that intercept all communication operations independent of the originating MPI call. This infrastructure can be used by creating submodules: two such submodules are included: an empty one that can be used as a template and one that prints every message. Note: this module relies on the status, requests, and datatype modules. A more detailed description on how to implemented submodules is included in the comm directory as a separate README.

  • limit-threading This PnMPI specific module limits the MPI threading level to the value set in the PNMPI_THREADING_LEVEL environment variable. It may be used to check the behavior of an application, if the MPI environment doesn't support a specific threading level.

  • metrics-counter This PnMPI specific module counts the MPI call invocations. Add the module at the top of your config file to count how often each rank invoked which MPI call or in front of a specific module to count how often invocations reached this module.

  • metrics-timing This PnMPI specific module measures the time MPI call invocations take. It has two different operation modes:

    • simple: Add it in front of a module and it will measure the time of all following modules.

      module metrics-timing
      module sample1
    • advanced: Add the timing module before and after the modules you want to measure and it will only measure the time of these, but not the following modules.

      module metrics-timing
      module sample1
      module sample2
      module metrics-timing
      module empty

      Measuring MPI_Pcontrol is available in advanced mode, only. To measure MPI_Pcontrol calls both metrics-timing invocations need to be pcontrol enabled:

      module metrics-timing
      pcontrol on # May be ignored if metrics-timing is the first module.
      module sample1
      module metrics-timing
      pcontrol on
  • wait-for-debugger This module prints the PID of each rank before executing the application. If the WAIT_AT_STARTUP environment variable is set to a numeric value, the execution will be delayed up to value seconds, so you may attach with a debugger in that time.

Note: All modules must be compiled with the same MPI as PnMPI is build with. Modules should only be linked to their required libraries, except PnMPI and MPI, as these routines will be provided by PnMPI when the module will be loaded.

D) Building your own modules with CMake

PnMPI installs CMake build files with its distribution to allow external projects to quickly build MPI tool modules. The build files allow external tools to use PnMPI, the pnmpi-patch utility, PnMPI's wrapper generator, and PnMPI's dependency libraries.

To create a new PnMPI module, simply create a new project that looks something like this:


Assume that wrapper.w is a wrapper generator input file that will generate another file called wrapper.c, which contains MPI interceptor functions for the tool library. foo.c is additional code needed for the tool library. CMakeLists.txt is the CMake build file.

Your CMakeLists.txt file should start with something like this:

project(my-module C)

find_package(PnMPI REQUIRED)
find_package(MPI REQUIRED)

add_wrapped_file(wrapper.c wrapper.w)
pnmpi_add_pmpi_module(foo foo.c wrapper.c)


  • project() and cmake_minimum_required() are standard. These tell the build the name of the project and what version of CMake it will need.

  • find_package(PnMPI) will try to find PnMPI in system locations, and if it is not found, it will fail because the REQUIRED option has been specified.

  • find_package(MPI) locates the system MPI installation so that you can use its variables in the CMakeLists.txt file.

  • add_wrapped_file() tells the build that wrapper.c is generated from wrapper.w, and it adds rules and dependencies to the build to automatically run the wrapper generator when wrapper.c is needed.

  • Finally, pnmpi_add_pmpi_module() function's much like CMake's builtin add_library() command, but it ensures that the PnMPI library is built as a loadable module and that the library is properly patched.

    If your module uses the XMPI interface (i.e. doesn't need to be patched), use pnmpi_add_xmpi_module() instead, so it will build the module but don't patch it.

  • install() functions just as it does in a standard CMake build, but here we install to the PnMPI_MODULES_DIR instead of an install-relative location. This variable is set if PnMPI is found by find_package(PnMPI), and it allows users to install directly into the system PnMPI installation.

  • Finally, include_directories() functions as it would in a normal CMake build.

Once you've make your CMakeLists.txt file like this, you can build your PnMPI module like so:

cd my-module
mkdir $SYS_TYPE && cd $SYS_TYPE
cmake ..
make -j8
make -j8 install

This should find PnMPI on your system and build your module, assuming that you have your environment set up correctly.

D2) Limiting the threading level

If your module is not thread safe or is only able to process a limited amount of threading, it should limit the required threading level in the MPI_Init_thread wrapper:

int MPI_Init_thread(int *argc, char ***argv, int required, int *provided)
  if (required > MPI_THREAD_SINGLE)
    required = MPI_THREAD_SINGLE;

  return XMPI_Init_thread(argc, argv, required, provided);

D3) Module hooks

At different points hooks will be called in all loaded modules. These can be used to trigger some functionality at a given time. All hooks have the return type void and are defined in pnmpi/hooks.h, which should be included for type safety. These following hooks will be called in all modules:

  • PNMPI_RegistrationPoint: This hook will be called just after the module has been loaded. It may be used to register the name of the module, services provided by the module, etc.
  • PNMPI_UnregistrationPoint: This hook will be called just before the module will be unloaded. It may be used e.g. to free allocated memory.
  • PNMPI_Init: This hook will be called just after all modules have been registered to initialize the module. It may be used to initialize the module's to code and is communicate with other modules.
  • PNMPI_Fini: This hook will be called just before all modules will be unregistered. The modules may communicate with each other and should execute some final steps in here.

Note: You can use PNMPI_Service_CallHook() to call custom hooks in your modules. Just pass a custom hook name as first parameter.

For a detailed description, see the Doxygen docs or man-pages for these functions.

D4) Module service functions

Modules may interact with the PnMPI core and other modules with the module service functions defined in pnmpi/service.h. For a detailed description about these functions, see the Doxygen docs for the service header or the man-pages.

D5) Debug message functions

Modules may print debug messages, warnings and errors with the PnMPI API functions PNMPI_Debug, PNMPI_Warning and PNMPI_Warning defined in pnmpi/debug_io.h. PnMPI will add additional informations like rank or line numbers to the printed messages.

For a detailed description, see the Doxygen docs or man-pages for these functions.

E) Debug Options

If PnMPI is build with ENABLE_DEBUG, PnMPI includes debug print functions, that can be dynamically enabled. To control it, the environment variable PNMPI_DBGLEVEL can be set to any combination of the following debug levels:

  • 0x01 - Messages about PnMPI initialization (before MPI is initialized).
  • 0x02 - Messages about module loading.
  • 0x04 - Messages about MPI call entry and exit.

NOTE: The first two levels should be enabled for single-rank executions only, as their output can't be limited to a single rank and thus will be printed on all ranks.

Additionally, the printouts can be restricted to a single node by setting the variable PNMPI_DBGNODE to an MPI rank.

E1) Using the PnMPI invocation tool

You may set the above options in the PnMPI invocation tool. Use the --debug option to enable a specific debug level and --debug-node to limit the debug output to a single rank.

F) Configuration and Demo codes

The PnMPI distribution includes test cases (in C and Fortran). They can be used to experiment with the basic PnMPI functionalities and to test the system setup. The following describes the C version (the F77 version works similarly):

  1. Change into the tests/src directory.

  2. The program test-mpi.c, which only initializes and then finalizes MPI, was compiled into three binaries:

    • testbin-binary_mpi_c-preload (plain MPI code)
    • testbin-binary_mpi_c-dynamic (linked dynamically against PnMPI)
    • testbin-binary_mpi_c-static (linked statically against PnMPI)
  3. Executing the *-preload binary will not print any output, but the binaries linked against PnMPI will print the PnMPI header, indicating PnMPI is loaded before MPI.

  4. PnMPI is configured through a configuration file that lists all modules to be load by PnMPI as well as optional arguments. The name for this file can be specified by the environment variable PNMPI_CONF. If this variable is not set or the file specified can not be found, PnMPI looks for a file called .pnmpi_conf in the current working directory, and if not found, in the user's home directory.

    A simple configuration file may look as follows:

    module sample1
    module sample2
    module sample3
    module sample4

(plus some additional lines starting with #, which indicates comments)

This configuration causes these four modules to be loaded in the specified order. PnMPI will look for the corresponding modules (.so shared library files) in PNMPI_LIB_PATH.

  1. Running the testbin-binary_mpi_sendrecv (a simple test sending messages between the ranks) will load all four modules in the specified order and intercept all MPI calls included in these modules:

    • sample1: send and receive
    • sample2: send
    • sample3: receive
    • sample4: send and receive

The program output (for 2 nodes) will be:

  _____   _ __   __  __  _____   _____
 |  __ \ | '_ \ |  \/  ||  __ \ |_   _|
 | |__) || | | || \  / || |__) |  | |
 |  ___/ |_| |_|| |\/| ||  ___/   | |
 | |            | |  | || |      _| |_
 |_|            |_|  |_||_|     |_____|

  MPI interface: C

 Global settings:
  Pcontrol: 5

 Loaded modules:
  Stack default:
    sample1 (Pcontrol: 1)

WRAPPER 1: Before recv
WRAPPER 1: Before send
WRAPPER 2: Before send
WRAPPER 4: Before send
WRAPPER 4: After send
WRAPPER 2: After send
WRAPPER 1: After send
WRAPPER 1: Before recv
WRAPPER 3: Before recv
WRAPPER 4: Before recv
WRAPPER 3: Before recv
WRAPPER 4: Before recv
WRAPPER 4: After recv
WRAPPER 3: After recv
WRAPPER 1: After recv
Got 1 from rank 1.
WRAPPER 1: Before send
WRAPPER 2: Before send
WRAPPER 4: Before send
WRAPPER 4: After send
WRAPPER 4: After recv
WRAPPER 3: After recv
WRAPPER 1: After recv
Got 1 from rank 0.
WRAPPER 2: After send
WRAPPER 1: After send

When running on a BG/P systems, it is necessary to explicitly export some environment variables. Here is an example:

    mpirun -np 4 -exp_env LD_LIBRARY_PATH -exp_env PNMPI_LIB_PATH \
      -cwd $PWD testbin-binary_mpi_sendrecv

G) Using MPI_Pcontrol

The MPI standard defines the MPI_Pcontrol, which does not have any direct effect (it is implemented as a dummy call inside of MPI), but that can be replaced by PMPI to accepts additional information from MPI applications (e.g., turn on/off data collection or markers for main iterations). The information is used by a PMPI tool linked to the application. When it is used with PnMPI the user must therefore decide which tool an MPI_Pcontrol call is directed to.

By default PnMPI will direct MPI_Pcontrol calls to first module in the tool stack only. If this is not the desired effect, users can turn on and off which module Pcontrols reach by adding pcontrol on and pcontrol off into the configuration file in a separate line following the corresponding module specification. Note that PnMPI allows that MPI_Pcontrol calls are sent to multiple modules.

In addition, the general behavior of Pcontrols can be specified with a global option at the beginning of the configuration file. This option is called globalpcontrol and can take one of the following arguments:

  • int: Only deliver the first argument, but ignore the variable list arguments (default)
  • pmpi: Forward the variable list arguments
  • pnmpi: Requires the application to specify a specific format in the variable argument list known to PnMPI (level must be PNMPI_PCONTROL_LEVEL)
  • mixed
    • Same as pnmpi, if level == PNMPI_PCONTROL_LEVEL.
    • Same as pmpi, if level != PNMPI_PCONTROL_LEVEL.
  • typed <tlevel> <type>: Forward the first argument in any case, the second only if the level matches <tlevel>. In this case, assume that the second argument is of type <type>.

The PnMPI internal format for Pcontrol arguments is as follows:

int level (same semantics as for MPI_Pcontrol itself)
               (target one or more modules) |
               (arguments as vargs or one pointer)
int mod = target module (if SINGLE)
int modnum = number of modules (if MULTIPLE)
int *mods = pointer to array of modules
int size = length of all variable arguments (if VARG)
void *buf = pointer to argument block (if PTR)

Known issues:

Forwarding the variable argument list as done in pmpi and mixed is only implemented in a highly experimental version and disabled by default. To enable, compile PnMPI with the flag EXPERIMENTAL_UNWIND and link PnMPI with the libunwind library. Note that this is not extensively tested and not portable across platforms.

H) References

More documentation on PnMPI can be found in the following two published articles:

  • Martin Schulz and Bronis R. de Supinski. PnMPI Tools: A Whole Lot Greater Than the Sum of Their Parts. Supercomputing 2007. November 2007, Reno, NV, USA.

    Available here.

  • Martin Schulz and Bronis R. de Supinski. A Flexible and Dynamic Infrastructure for MPI Tool Interoperability. International Conference on Parallel Processing (ICPP). August 2005, Columbus, OH, USA. Published by IEEE Press

    Available here.

I) Contact

For more information or in case of questions, please contact Martin Schulz or file an issue.


Copyright © 2008-2019 Lawrence Livermore National Security, LLC.
Copyright © 2011-2016 ZIH, Technische Universitaet Dresden, Federal Republic of Germany
Copyright © 2013-2019 RWTH Aachen University, Federal Republic of Germany

All rights reserved - please read the information in the LICENSE file.