How to find the number of cores available for MPI (4PY)?

Question

How to find the number of cores available for MPI (4PY)?

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Motivation

My Python program runs MPI instances hierarchically.

The first appearance always occurs and creates 4 instances. It makes no sense to increase this number due to the structure of my calculations, so I hard-coded it.

Depending on the command line parameters of the main program, each of the 4 instances invokes external Python software that scales almost linearly.

I call this external software using

N=3
child=MPI.COMM_SELF.Spawn(sys.executable,args=[`external.py`],maxprocs=N)

At the moment I use N=3, so that in 4 copies of the first caviar 3 copies of the external program appear each time, which gives a total of 12 copies, comparing the number of cores on my workstation.

However, for portability, I would like to do

N_avail = <MPI.N_CORES> #on my workstation: N_avail=12
N = N_avail/MPI.COMM_WORLD.Get_size() #on my workstation: N=12/4=3

.

, ?

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, maxprocs , mpirun out -np , . , Spawn maxprocs=1.

, ( ) 4 N_avail.

multiprocessing.cpu_count(), node ( ). SLURM.

Answer 1

, : MPI_UNIVERSE_SIZE. . MPI, http://mpi-forum.org/docs/mpi-3.1/mpi31-report/node253.htm#Node253

MPI MPI_COMM_WORLD, MPI_UNIVERSE_SIZE, . .... MPI_COMM_WORLD MPI_UNIVERSE_SIZE, , ....

mpi4py :

from mpi4py import MPI

version= MPI.Get_version()
print "mpi version is ",version

comm = MPI.COMM_WORLD
rank = comm.Get_rank()
size = comm.Get_size()
print "size is ",size

universe_size=comm.Get_attr(MPI.UNIVERSE_SIZE)
print "universe size is ",universe_size

mpirun OpenMPI, , :

mpirun -np 1 -H localhost,localhost,localhost python main.py

MPI 3, MPI_Info MPI_INFO_ENV . , :

maxprocs MPI .

soft .

mpi4py, :

soft=MPI.INFO_ENV.get("soft")
print soft
maxprocs=MPI.INFO_ENV.get("maxprocs")
print maxprocs