Learning by doing :: MPI -- Virtual Topologies In MPI, Part 5

This video is part of the new series called "Learning by doing :: MPI" which serves as an introductory course on MPI (Message Passing Interface). In this video we talked about virtual topologies in MPI! This topic corresponds to chapter 8 of the MPI standard v4.1. It is a lengthy chapter with a lot of information to digest. We followed the same pattern as for "Datatypes in MPI" by dividing a chapter into digestible ~25 mins long parts. In part 5 we continued our discussion by looking into the example which we replicated from the MPI standard(exp. 8.5) with the name of mpi_graph_topology_inquiry.c. Then we moved on with MPI_Dist_graph_neighbors_count and MPI_Dist_graph_neighbors which are similar to its cousins for graphs. We stressed on the fact that MPI_Dist_graph_neighbors* are only usable with distributed graphs and NOT graphs! Similarly MPI_Graph_neighbors* is only usable with graphs and NOT distributed graphs. Then we moved on MPI_Cart _shift which one can use to find the neighbors if one wants to perform communications along certain axes in the cartesian grid! We also mentioned that this function returns MPI_PROC_NULL if you are out of bound and your grid is not periodic. However, if your grid is periodic in any specific dimension, it will find the proper neighbor depending on the displacement you feed into it.

All the necessary info you need for MPI standard can be downloaded from here : https://www.mpi-forum.org/docs/mpi-4....

If you want to download MPICH, please visit here : https://www.mpich.org/downloads/
* The latest version at the time of this video is mpich-4.2.2

Hope you learned something from this video. If you have further questions don't hesitate to comment down below. Have fun!