@raovgarimella I'd like to add a capability to partition based on a user-provided file. The attached pull request works in the one simple file example I've tried. It is a bit weird because there is no way of providing MESH_Get_Partition with a filename option, so currently the filename is hard-coded as "./coloring.bin".

The file format is simply a bunch of ints, one per region, defining the color (from 0 to NPROC).

The implementation simply mallocs parts, then reads it from file in a single block. To write this file, one must write a C binary file, which can be done in C or in python, e.g. for a four-cell problem:

import struct
with open('coloring.bin', 'wb') as fid:
    for i in [0,0,1,1]:
        fid.write(struct.pack('i', i))

At first glance this worked for me, and allowed meshconvert to partition this file as requested (using partition-method=3).