ACENET Summer School - MPI: Glossary

mpirun starts any program

srun does same as mpirun inside a Slurm job

mpirun and srun get task count from Slurm context

C requires #include <mpi.h> and is compiled with mpicc

Fortran requires use mpi and is compiled with mpif90

commands mpicc, mpif90 and others are wrappers around compilers

MPI processes have rank from 0 to size-1

MPI_COMM_WORLD is the ordered set of all processes

Functions MPI_Init, MPI_Finalize, MPI_Comm_size, MPI_Comm_rank are fundamental to any MPI program

Functions MPI_Ssend, MPI_Recv

Types MPI_CHAR, MPI_Status

A typical MPI process calculates which other processes it will communicate with.

If there is a closed loop of procs sending to one another, there is a risk of deadlock.

All sends and receives must be paired, at time of sending.

Types MPI_DOUBLE (C), MPI_DOUBLE_PRECISION (Ftn)

Constants MPI_PROC_NULL, MPI_ANY_SOURCE

There are advanced MPI routines that solve most common problems. Don’t reinvent the wheel.

Function MPI_SendRecv

Collective operations involve all processes in the communicator.

Functions MPI_Reduce, MPI_AllReduce

Types MPI_FLOAT (C), MPI_REAL (Ftn)

Constants MPI_MIN, MPI_MAX, MPI_SUM

Finite differences, stencils, guard cells