Redirect stdout from MPI_Comm_spawn to a file in mpi4py

[Pavankumar Koratikere]

I have a runscript.py file that outputs a lot of stdout on the terminal. I run the script from command line using mpirun -n 8 python runscript.py >> analysis.log which redirects the stdout to analysis.log file.

Instead of running the script from command line, I am using MPI.COMM_WORLD.Spawn(sys.executable, args=["runscript.py"], maxprocs=8) from another script. I want to redirect stdout from only the spawned process and not from the main script. Is there a way to redirect stdout to a file from child processes spawned using MPI.COMM_WORLD.Spawn() method?

OpenMPI: 4.0.7
mpi4py: 3.1.3

[Lisandro Dalcin]

I don't really know. Ultimately, the behavior would depend on the backend MPI implementation, this is not something mpi4py has control of. You should ask Open MPI folks.

[Pavankumar Koratikere]

I found a way to do this by changing the file descriptor from python using os.dup().

[William Handley]

> I found a way to do this by changing the file descriptor from python using os.dup().

Could you give any more detail?

[Pavankumar Koratikere]

You can checkout this question on stack overflow: https://stackoverflow.com/questions/68716139/redirecting-current-runing-python-process-stdout

Answer provides an example of how to use os.dup()