vspetrov/mt_stress

Multi-threaded MPI stress test

* BUILD
  mpicc mt_stress.c -g -o mt_stress

* RUN: having NNODES, PPN ranks per node AND NT threads per rank
  mpirun -np $((NNODES*PPN/NT)) --map-by socket:span --bind-to socket ./mt_stress --n-threads=4 --n-splits 300 --tests-per-comm 32