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JohannesBuchner / UltraNest

Fit and compare complex models reliably and rapidly. Advanced nested sampling.
https://johannesbuchner.github.io/UltraNest/
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Parallel execution of UltraNest inside a python script #67

Closed EduardoCristo closed 2 years ago

EduardoCristo commented 2 years ago

Description

Hi Joahannes! Is there any efficient way to run UltraNest in parallel inside a Python script? I can't use mpirun to run the main since it messes the parallelization of other part of the code.

What I Did

I coded a script to call UltraNest outside the main code, running it with os.system("mpirun -np x ultranest_script.py ..."). However, I'm having problems passing the function arguments. I'm convinced it must exist a better way of doing it.

Cheers, Eduardo.

arnauqb commented 2 years ago

Why don't you just wrap your serial part of the code in an if statement

from mpi4py import MPI
mpi_comm = MPI.COMM_WORLD
mpi_rank = mpi_comm.Get_rank()

if mpi_rank == 0:
     # part of the code that runs in serial
JohannesBuchner commented 2 years ago

I usually write a data preparation script, a analysis script and a plotting script, but @arnauqb's suggestion solves the messing up. you can also ask sampler.mpi_rank, I think.

To pass arguments, if the data structures are complicated, you could use a file (json/hdf5). Otherwise have a look at the argparse library to make a robust script and input parsing.