Hello all,
Sorry for the newbie question, but is there a way of making petsc4py work with
an MPI group or subcommunicator? I saw a solution posted back in 2010
(http://lists.mcs.anl.gov/pipermail/petsc-users/2010-May/006382.html), but it
does not work for me. Indeed, if I try to use petsc4py.init(comm=newcom), then
my sample code prints a msg "Attempting to use an MPI routine before
initializing MPI". Below I attach both the output and the source of the python
code.
kind regards
Rodrigo
time mpirun -n 5 python split_comm_ex2.py
Global: rank 0 of 5. New comm : rank 0 of 3
Global: rank 1 of 5. New comm : rank 0 of 2
Global: rank 2 of 5. New comm : rank 1 of 3
Global: rank 3 of 5. New comm : rank 1 of 2
Global: rank 4 of 5. New comm : rank 2 of 3
Attempting to use an MPI routine before initializing MPI
Attempting to use an MPI routine before initializing MPI
real 0m0.655s
user 0m1.122s
sys 0m1.047s
And the python code:
from mpi4py import MPI
comm = MPI.COMM_WORLD
world_rank = comm.rank
world_size = comm.size
color = world_rank % 2
newcomm = comm.Split(color)
newcomm_rank = newcomm.rank
newcomm_size = newcomm.size
for i in range(world_size):
comm.Barrier()
if (world_rank == i):
print ("Global: rank %d of %d. New comm : rank % d of %d" %
(world_rank, world_size, newcomm_rank, newcomm_size))
if newcomm.rank == 0:
import petsc4py
petsc4py.init(comm=newcomm)
from petsc4py import PETSc
pcomm = PETSc.COMM_WORLD
print('pcomm size is {}/{}'.format(pcomm.rank, pcomm.size))
newcomm.Free()
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