Singularity support mpich

Just try creating the wiki page, you can delete the content if you consider it is not reasonable.

Try mpich using Singularity:

The Singularity website just announced supporting openmpi version 2.1. Good news is I also try mpich in these days, Singularity also work on mpich 3.1.3.

ENV:
singularity image is centos7.3,
host os is centos 7.3,
singularity uses the latest code from git clone,
example is pi running on 2 nodes.

[root@gpu1 /]# mpirun -np 2 -hosts gpu1,gpu2 singularity exec /share/centosmpich.img /tmp/prog

Enter the number of intervals: (0 quits) pi is approximately 3.1415926535895737, Error is 0.0000000000002194
wall clock time = 12.751852
Enter the number of intervals: (0 quits) No number entered; quitting