...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Getting started with Boost.MPI requires a working MPI implementation, a recent version of Boost, and some configuration information.
To get started with Boost.MPI, you will first need a working MPI implementation. There are many conforming MPI implementations available. Boost.MPI should work with any of the implementations, although it has only been tested extensively with:
You can test your implementation using the following simple program, which passes a message from one processor to another. Each processor prints a message to standard output.
#include <mpi.h> #include <iostream> int main(int argc, char* argv[]) { MPI_Init(&argc, &argv); int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); if (rank == 0) { int value = 17; int result = MPI_Send(&value, 1, MPI_INT, 1, 0, MPI_COMM_WORLD); if (result == MPI_SUCCESS) std::cout << "Rank 0 OK!" << std::endl; } else if (rank == 1) { int value; int result = MPI_Recv(&value, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); if (result == MPI_SUCCESS && value == 17) std::cout << "Rank 1 OK!" << std::endl; } MPI_Finalize(); return 0; }
You should compile and run this program on two processors. To do this, consult
the documentation for your MPI implementation. With OpenMPI,
for instance, you compile with the mpiCC
or mpic++
compiler, boot the LAM/MPI daemon, and run your program via mpirun
. For instance, if your program is
called mpi-test.cpp
,
use the following commands:
mpiCC -o mpi-test mpi-test.cpp lamboot mpirun -np 2 ./mpi-test lamhalt
When you run this program, you will see both Rank
0 OK!
and Rank
1 OK!
printed to the screen. However, they may
be printed in any order and may even overlap each other. The following output
is perfectly legitimate for this MPI program:
Rank Rank 1 OK! 0 OK!
If your output looks something like the above, your MPI implementation appears to be working with a C++ compiler and we're ready to move on.
As the rest of Boost, Boost.MPI uses version 2 of the Boost.Build system for configuring and building the library binary.
Please refer to the general Boost installation instructions for Unix Variant (including Unix, Linux and MacOS) or Windows. The simplified build instructions should apply on most platforms with a few specific modifications described below.
As described in the boost installation instructions, go to to root of your
Boost source distribution and run the bootstrap
script (./bootstrap.sh
for
unix variants or bootstrap.bat
for Windows). That will generate a 'project-config.jam` file in the root
directory. Use your favourite text editor and add the following line:
using mpi ;
Alternatively, you can provided explicitly the list of Boost libraries
you want to build. Please refer to the --help
option of
the
bootstrap` script.
First, you need to scan the include/boost/mpi/config.hpp
file and check if some settings needs to be modified for your MPI implementation
or preferences.
In particular, the BOOST_MPI_HOMOGENEOUS
macro, that you will need to comment out if you plan to run on an heterogeneous
set of machines. See the optimization
notes below.
Most MPI implementations requires specific compilation and link options. In order to mask theses options to the user, most MPI implementations provides wrappers which silently pass those options to the compiler.
Depending on your MPI implementation, some work might be needed to tell
Boost which specific MPI option to use. This is done through the using mpi ;
directive of the project-config.jam
file.
The general form is the following (do not forget to leave spaces around : and before ;):
using mpi : [<MPI compiler wrapper>] : [<compilation and link options>] : [<mpi runner>] ;
For those who uses MPICH2,
OpenMPI or some of their derivatives,
configuration can be almost automatic. In fact, if your mpicxx
command is in your path, you just need to use:
using mpi ;
The directive will find the wrapper and deduce the options to use.
...or if it does not have a usual wrapper name, you will need to tell the build system where to find it:
using mpi : /opt/mpi/bullxmpi/1.2.8.3/bin/mpicc ;
or does not exist at all (it happens), you need to provide the compilation
and build options to the build environment using jam
directives. For example, the following could be used for a specific Intel
MPI implementation:
using mpi : mpiicc : <library-path>/softs/intel/impi/5.0.1.035/intel64/lib <library-path>/softs/intel/impi/5.0.1.035/intel64/lib/release_mt <include>/softs/intel/impi/5.0.1.035/intel64/include <find-shared-library>mpifort <find-shared-library>mpi_mt <find-shared-library>mpigi <find-shared-library>dl <find-shared-library>rt ;
To do that, you need to guess the libraries and include directories associated
with your environment. You can refer to the your specific MPI environment
documentation. Most of the time though, your wrapper have an option that
provide that information, it usually starts with --show
:
$ mpiicc -show icc -I/softs/.../include ... -L/softs/.../lib ... -Xlinker -rpath -Xlinker /softs/.../lib .... -lmpi -ldl -lrt -lpthread $
$ mpicc --showme icc -I/opt/.../include -pthread -L/opt/.../lib -lmpi -ldl -lm -lnuma -Wl,--export-dynamic -lrt -lnsl -lutil -lm -ldl $ mpicc --showme:compile -I/opt/mpi/bullxmpi/1.2.8.3/include -pthread $ mpicc --showme:link -pthread -L/opt/.../lib -lmpi -ldl -lm -lnuma -Wl,--export-dynamic -lrt -lnsl -lutil -lm -ldl $
To see the results of MPI auto-detection, pass --debug-configuration
on the bjam command line.
...Which is a good thing.
The (optional) third argument configures Boost.MPI for running regression tests. These parameters specify the executable used to launch jobs (the default is "mpirun") followed by any necessary arguments to this to run tests and tell the program to expect the number of processors to follow (default: "-np"). With the default parameters, for instance, the test harness will execute, e.g.,
mpirun -np 4 all_gather_test
Some implementations provides alternative launcher that can be more convenient.
For example, Intel's MPI provides the mpiexec.hydra
:
$mpiexec.hydra -np 4 all_gather_test
which does not requires any daemon to be running (as opposed to their
mpirun
command). Such a
launcher need to be specified though:
using mpi : mpiicc : ..... : mpiexec.hydra -n ;
To build the whole Boost distribution:
$cd <boost distribution> $./b2 install
Tip | |
---|---|
Or, if you have a multi-cpu machine (say 24): $cd <boost distribution> $./b2 -j24 install |
Installation of Boost.MPI can be performed in the build step by specifying
install
on the command
line and (optionally) providing an installation location, e.g.,
$./b2 install
This command will install libraries into a default system location. To
change the path where libraries will be installed, add the option --prefix=PATH
.
Then, you can run the regression tests with:
$cd <boost distribution/lib/mpi/test
$....../b2
To build applications based on Boost.MPI, compile and link them as you normally
would for MPI programs, but remember to link against the boost_mpi
and boost_serialization
libraries,
e.g.,
mpic++ -I/path/to/boost/mpi my_application.cpp -Llibdir \ -lboost_mpi-gcc-mt-1_35 -lboost_serialization-gcc-d-1_35.a
If you plan to use the Python bindings
for Boost.MPI in conjunction with the C++ Boost.MPI, you will also need to
link against the boost_mpi_python library, e.g., by adding -lboost_mpi_python-gcc-mt-1_35
to your link command. This step will
only be necessary if you intend to register
C++ types or use the skeleton/content
mechanism from within Python.