MPI Topics on the HPE Cray EX Supercomputer

Presenter: Harvey Richardson (HPE)

Archived materials on LUMI:

• Slides: /appl/local/training/4day-20241028/files/LUMI-4day-20241028-3_05_Cray_MPI_on_Slingshot.pdf

• Recording: /appl/local/training/4day-20241028/recordings/3_05_Cray_MPI_on_Slingshot.mp4

These materials can only be distributed to actual users of LUMI (active user account).

Q&A

1. For the 2D neighbour exchange example on the slides, isn't it easier to let MPI_Cart_create() deal with the reordering and just use whatever it returns? And then ask the MPI_Cart_shift() for neighbours?

   • Cart may not create an optimal solution. It may not be aware about things like node-layout and NUMA domains.