MPI

This page includes

Introduction to MPI,
Introduction to MPI4py,
I will include some programming idioms for MPI4py.

The code used to develop this information will be probably be hosted somewhere in GitHub.

Spawning VASP from MPI4Py

This task is taking me a little while to figure out.

https://mpi4py.scipy.org/docs/usrman/tutorial.html#compute-pi

Spawning a binary from within MPI4PY is a somewhat difficult task, but necessary when doing certain types of calculations.

$VASP_BIN=vasp_std

$MPI4PY_MPI_SO=MPI.so

ldd $VASP_BIN

ldd $MPI4PY_MPI_SO

check to see that the shared libraries match

import sys

from mpi4py import MPI

assert MPI.COMM_WORLD.Get_size() == 1

nvprof = 'nvprof'

program = './myprogram'

nprocs = 8

command, args = [], []

for i in range(nprocs):

    command.append(nvprof)

args.append([program, '-o', 'outfile.%d.log' % i])

MPI.COMM_WORLD.Spawn_multiple(command, args).Free()

MPI_BCAST

MPI_BCAST(BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)

MPI Datatype List in F90 and C

F90 MPI DataType     F90 Meaning        C MPI DataType      C Meaning ----------------     ---------------    --------------      --------------- MPI_INTEGER          INTEGER            MPI_INT             (signed) int MPI_REAL             REAL               MPI_FLOAT           float MPI_DOUBLE_PRECISION REAL*8             MPI_DOUBLE          double                                         MPI_LONG_DOUBLE     long double MPI_COMPLEX          COMPLEX MPI_LOGICAL          LOGICAL MPI_CHARACTER        CHARACTER(1)       MPI_SIGNED_CHAR     signed cahr                                         MPI_UNSIGNED_CHAR   unsigned cahr                                         MPI_SHORT           signed short int                                         MPI_LONG            signed long int                                         MPI_UNSIGNED        unsigned int                                         MPI_UNSIGNED_SHORT  unsigned short int                                         MPI_UNSIGNED_LONG   unsigned long int MPI_BYTE                                MPI_BYTE MPI_PACKED                              MPI_PACKED

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