parallel.rst

Parallel Implementation

Parallel implementation in parmest is preliminary. To run parmest in parallel, you need the mpi4py Python package and a compatible MPI installation. If you do NOT have mpi4py or a MPI installation, parmest still works (you should not get MPI import errors).

For example, the following command can be used to run the semibatch model in parallel:

mpiexec -n 4 python parallel_example.py

The file parallel_example.py is shown below. Results are saved to file for later analysis.

../../../../pyomo/contrib/parmest/examples/semibatch/parallel_example.py

Installation

The mpi4py Python package should be installed using conda. The following installation instructions were tested on a Mac with Python 3.5.

Create a conda environment and install mpi4py using the following commands:

conda create -n parmest-parallel python=3.5
source activate parmest-parallel
conda install -c conda-forge mpi4py

This should install libgfortran, mpi, mpi4py, and openmpi.

To verify proper installation, create a Python file with the following:

from mpi4py import MPI
import time 
comm = MPI.COMM_WORLD 
rank = comm.Get_rank() 
print('Rank = ',rank)
time.sleep(10) 

Save the file as test_mpi.py and run the following command:

time mpiexec -n 4 python test_mpi.py 
time python test_mpi.py 

The first one should be faster and should start 4 instances of Python.