This chapter provides procedures for building MPI applications. It provides examples of the use of the mpirun(1) command to launch MPI jobs. It also provides procedures for building and running SHMEM applications.
The default locations for the include files, the .so files, the .a files, and the mpirun command are pulled in automatically. Once the MPT RPM is installed as default, the commands to build an MPI-based application using the .so files are as follows:
To compile using GNU compilers, choose one of the following commands:
% g++ -o myprog myprog.C -lmpi++ -lmpi % gcc -o myprog myprog.c -lmpi % g77 -I/usr/include -o myprog myprog.f -lmpi
To compile programs with the Intel compiler, use the following commands:
% efc -o myprog myprog.f -lmpi (Fortran - version 7.1) % ecc -o myprog myprog.c -lmpi (C - version 7.1) % ifort -o myprog myprog.f -lmpi (Fortran - version 8) % icc -o myprog myprog.c -lmpi (C - version 8)
The libmpi++.so library is compatible with code generated by g++ 3.0 or later compilers, as well as Intel C++ 8.0 or later compilers. If compatibility with previous g++ or C++ compilers is required, the libmpi++.so released with MPT 1.9 (or earlier) must be used.
Note: You must use the Intel compiler to compile Fortran 90 programs. To compile Fortran programs with the Intel compiler, enabling compile-time checking of MPI subroutine calls, insert a USE MPI statement near the beginning of each subprogram to be checked and use one of the following commands:
% efc -I/usr/include -o myprog myprog.f -lmpi (version 7.1) % ifort -I/usr/include -o myprog myprog.f -lmpi (version 8)
Note: The above command line assumes a default installation; if you have installed MPT into a non-default location, replace /usr/include with the name of the relocated directory.
You must use the mpirun command to start MPI applications. For complete specification of the command line syntax, see the mpirun(1) man page. This section summarizes the procedures for launching an MPI application.
To run an application on the local host, enter the mpirun command with the -np argument. Your entry must include the number of processes to run and the name of the MPI executable file.
The following example starts three instances of the mtest application, which is passed an argument list (arguments are optional):
% mpirun -np 3 mtest 1000 "arg2" |
You are not required to use a different host in each entry that you specify on the mpirun command. You can launch a job that has multiple executable files on the same host. In the following example, one copy of prog1 and five copies of prog2 are run on the local host. Both executable files use shared memory.
% mpirun -np 1 prog1 : 5 prog2 |
You can use the mpirun command to launch a program that consists of any number of executable files and processes and you can distribute the program to any number of hosts. A host is usually a single machine, or it can be any accessible computer running Array Services software. For available nodes on systems running Array Services software, see the /usr/lib/array/arrayd.conf file.
You can list multiple entries on the mpirun command line. Each entry contains an MPI executable file and a combination of hosts and process counts for running it. This gives you the ability to start different executable files on the same or different hosts as part of the same MPI application.
The examples in this section show various ways to launch an application that consists of multiple MPI executable files on multiple hosts.
The following example runs ten instances of the a.out file on host_a:
% mpirun host_a -np 10 a.out |
When specifying multiple hosts, you can omit the -np option and list the number of processes directly. The following example launches ten instances of fred on three hosts. fred has two input arguments.
% mpirun host_a, host_b, host_c 10 fred arg1 arg2 |
The following example launches an MPI application on different hosts with different numbers of processes and executable files:
% mpirun host_a 6 a.out : host_b 26 b.out |
To use the MPI-2 process creation functions MPI_Comm_spawn or MPI_Comm_spawn_multiple, you must specify the universe size by specifying the -up option on the mpirun command line. For example, the following command starts three instances of the mtest MPI application in a universe of size 10:
% mpirun -up 10 -np 3 mtest |
By using one of the above MPI spawn functions, mtest can start up to seven more MPI processes.
When running MPI applications on partitioned Altix systems which use the MPI-2 MPI_Comm_spawn or MPI_Comm_spawn_multiple functions, it may be necessary to explicitly specify the partitions on which additional MPI processes may be launched. See the section "Launching Spawn Capable Jobs on Altix Partitioned Systems" on the mpirun(1) man page.
To compile SHMEM programs with a GNU compiler, choose one of the following commands:
% g++ compute.C -lsma % gcc compute.c -lsma % g77 -I/usr/include compute.f -lsma |
To compile SHMEM programs with the Intel compiler, use the following commands:
% ecc compute.C -lsma (version 7.1) % ecc compute.c -lsma (version 7.1) % efc compute.f -lsma (version 7.1) % icc compute.C -lsma (version 8) % icc compute.c -lsma (version 8) % ifort compute.f -lsma (version 8) |
You must use mpirun to launch SHMEM applications. The NPES variable has no effect on SHMEM programs. To request the desired number of processes to launch, you must set the -np option on mpirun.
The SHMEM programming model supports single host SHMEM applications, as well as SHMEM applications that span multiple partitions. To launch a SHMEM application on more than one partition, use the multiple host mpirun syntax, such as the following:
% mpirun hostA, hostB -np 16 ./shmem_app |
For more information, see the intro_shmem(3) man page.