mpi list

This package implements the DFM class.

The DFM is a useful abstraction for working with lists distributed over a set of MPI ranks. The acronym stands for distributed free monoid, which is just a fancy way to say it’s a list.

If you’re familiar with spark, it’s like an RDD, but only holds a list.

Quick Start

from mpi_list import Context, DFM

C = Context() # calls MPI_Init via mpi4py

# After each of the three lines below:
#  1. each rank now has 1000//C.procs consecutive numbers
#  2. each rank now has a list of strings
#  3. only numbers containing a '2' remain
dfm = C . iterates(1000) \
        . map(lambda i: f"String {i}") \
        . filter(lambda s: '2' in s)

if C.rank == 0:
    # Caution! Uncommenting this will deadlock your program.
    # Collective calls must be called by all ranks!
    #print( dfm . head(10) )

# This is OK, since all ranks now have 'ans'
ans = dfm.head(10)
if C.rank == 0:
    print( ans )

ans = dfm . filter(lambda s: len(s) <= len("String nn")) \
          . collect()
if ans is not None: # only rank 0 gets "collect"
    print( ans )

Launch your program with mpirun python

If you’re using a supercomputer, consider installing spindle, and then use spindle mpirun python


This project has been set up using PyScaffold 4.0.1. For details and usage information on PyScaffold see