# Message Passing Interface (MPI) Start with a simple mpi program (`mpi_hello.c`): ```c #include #include int main(int argc, char** argv) { // Initialize the MPI environment MPI_Init(NULL, NULL); // Get the number of processes int world_size; MPI_Comm_size(MPI_COMM_WORLD, &world_size); // Get the rank of the process int world_rank; MPI_Comm_rank(MPI_COMM_WORLD, &world_rank); // Get the name of the processor char processor_name[MPI_MAX_PROCESSOR_NAME]; int name_len; MPI_Get_processor_name(processor_name, &name_len); // Print off a hello world message printf("Hello world from processor %s, rank %d out of %d processors\n", processor_name, world_rank, world_size); // Finalize the MPI environment. MPI_Finalize(); } ``` To compile, ``` module load mpi/openmpi-x86_64 which mpicc /usr/lib64/openmpi/bin/mpicc -o mpi_hello mpi_hello.c ``` To run interactively, ``` mpirun -n 4 mpi_hello ``` Note that, there are few mpi modules installed in the system. You can check with `module available` ```bash module available ------------------------------------------------------------------------------------ /work/app/modules/modules/all ------------------------------------------------------------------------------------- Anaconda3/5.3.0 LibTIFF/4.0.10-GCCcore-8.3.0 XZ/5.2.4-GCCcore-8.3.0 libjpeg-turbo/2.0.3-GCCcore-8.3.0 Autoconf/2.69-GCCcore-8.3.0 M4/1.4.18-GCCcore-8.3.0 binutils/2.32-GCCcore-8.3.0 libpciaccess/0.14-GCCcore-8.3.0 Automake/1.16.1-GCCcore-8.3.0 M4/1.4.18 (D) binutils/2.32 (D) libpng/1.6.37-GCCcore-8.3.0 Autotools/20180311-GCCcore-8.3.0 MPFR/4.0.2-GCCcore-8.3.0 bzip2/1.0.8-GCCcore-8.3.0 libreadline/8.0-GCCcore-8.3.0 Bison/3.3.2-GCCcore-8.3.0 NASM/2.14.02-GCCcore-8.3.0 cURL/7.66.0-GCCcore-8.3.0 libtool/2.4.6-GCCcore-8.3.0 Bison/3.3.2 (D) Ninja/1.9.0-GCCcore-8.3.0 expat/2.2.7-GCCcore-8.3.0 libxml2/2.9.9-GCCcore-8.3.0 CMake/3.15.3-GCCcore-8.3.0 OpenBLAS/0.3.7-GCC-8.3.0 flex/2.6.4-GCCcore-8.3.0 libyaml/0.2.2-GCCcore-8.3.0 CUDA/10.1.243-GCC-8.3.0 OpenMPI/4.0.1-GCC-8.3.0-2.32 flex/2.6.4 (D) ncurses/6.0 DB/18.1.32-GCCcore-8.3.0 Perl/5.30.0-GCCcore-8.3.0 freetype/2.10.1-GCCcore-8.3.0 ncurses/6.1-GCCcore-8.3.0 (D) EasyBuild/4.3.2 Pillow-SIMD/6.0.x.post0-GCCcore-8.3.0 gcccuda/2019b numactl/2.0.12-GCCcore-8.3.0 Eigen/3.3.7 Pillow/6.2.1-GCCcore-8.3.0 gettext/0.19.8.1 protobuf/3.10.0-GCCcore-8.3.0 GCC/4.8.1 PyYAML/5.1.2-GCCcore-8.3.0 help2man/1.47.4 pybind11/2.4.3-GCCcore-8.3.0-Python-3.7.4 GCC/8.3.0 Python/2.7.16-GCCcore-8.3.0 help2man/1.47.8-GCCcore-8.3.0 (D) xorg-macros/1.19.2-GCCcore-8.3.0 GCC/8.3.0-2.32 (D) Python/3.7.4-GCCcore-8.3.0 (D) hwloc/2.0.3-GCCcore-8.3.0 zlib/1.2.11-GCCcore-8.3.0 GCCcore/8.3.0 SQLite/3.29.0-GCCcore-8.3.0 hypothesis/4.44.2-GCCcore-8.3.0-Python-3.7.4 zlib/1.2.11 (D) GMP/6.1.2-GCCcore-8.3.0 Tcl/8.6.9-GCCcore-8.3.0 libffi/3.2.1-GCCcore-8.3.0 ------------------------------------------------------------------------------------------- /etc/modulefiles ------------------------------------------------------------------------------------------- mpi/mpich-x86_64 mpi/mpich-3.0-x86_64 mpi/mpich-3.2-x86_64 mpi/openmpi-x86_64 (L) mpi/openmpi3-x86_64 (D) ``` Example of the submission script, ```bash #!/bin/bash # #SBATCH --qos=cu_hpc #SBATCH --partition=cpugpu #SBATCH --job-name=example6 #SBATCH --output=example6_log.txt #SBATCH --ntasks=28 #SBATCH --tasks-per-node=4 #SBATCH --mem-per-cpu=1G #SBATCH --time=00:10:00 module purge module load mpi/openmpi-x86_64 srun ./mpi_hello ``` Example of the output, ``` ========================================== SLURM_JOB_ID = 82971 SLURM_NODELIST = gpu-1-[01-07] ========================================== Hello world from processor gpu-1-01, rank 0 out of 1 processors Hello world from processor gpu-1-01, rank 0 out of 1 processors Hello world from processor gpu-1-01, rank 0 out of 1 processors Hello world from processor gpu-1-01, rank 0 out of 1 processors Hello world from processor gpu-1-02, rank 0 out of 1 processors Hello world from processor gpu-1-03, rank 0 out of 1 processors Hello world from processor gpu-1-02, rank 0 out of 1 processors Hello world from processor gpu-1-02, rank 0 out of 1 processors Hello world from processor gpu-1-02, rank 0 out of 1 processors Hello world from processor gpu-1-05, rank 0 out of 1 processors Hello world from processor gpu-1-03, rank 0 out of 1 processors Hello world from processor gpu-1-03, rank 0 out of 1 processors Hello world from processor gpu-1-03, rank 0 out of 1 processors Hello world from processor gpu-1-07, rank 0 out of 1 processors Hello world from processor gpu-1-05, rank 0 out of 1 processors Hello world from processor gpu-1-05, rank 0 out of 1 processors Hello world from processor gpu-1-05, rank 0 out of 1 processors Hello world from processor gpu-1-04, rank 0 out of 1 processors Hello world from processor gpu-1-07, rank 0 out of 1 processors Hello world from processor gpu-1-07, rank 0 out of 1 processors Hello world from processor gpu-1-07, rank 0 out of 1 processors Hello world from processor gpu-1-04, rank 0 out of 1 processors Hello world from processor gpu-1-04, rank 0 out of 1 processors Hello world from processor gpu-1-04, rank 0 out of 1 processors Hello world from processor gpu-1-06, rank 0 out of 1 processors Hello world from processor gpu-1-06, rank 0 out of 1 processors Hello world from processor gpu-1-06, rank 0 out of 1 processors Hello world from processor gpu-1-06, rank 0 out of 1 processors ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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