If I want to remap processes-core for MPI program, can I migrate after those are spawned? For example: Node 1 have: P0,P3,P6 and Node 2 have: P1,P4,P7. Can I migrate P1 to Node 1? Topology aware MPI suggests remapping in research papers. That hints of picking a process and put it into such a node that provides best result. Is it possible to do?
Is it possible to migrate one process from one core of a node to another core of another node in MPI?
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To go off of what Victor said:
MPI-libraries do allow you to manually place processes via the use of a hostfile and/or mpirun-based flags (be it inside MPICH, OpenMPI, MVAPICH2, etc.). Profiling your application via something like TAU and viewing a communication matrix (see tau.uoregon.edu for documentation) before choosing the "best" process mapping for your application.
No. MPI does not have any migration functionality. Topology-aware MPI (which as you remark is pretty much research level, not production) uses knowledge of how the application communicates to map ranks to nodes. Normally ranks are put on successive nodes; if you have knowledge about what ranks often communicate, they can be mapped closer together.