#1850: Severe performance problem on Stampede -------------------------+-------------------------------------------------- Reporter: hinder | Owner: Type: defect | Status: confirmed Priority: major | Milestone: Component: SimFactory | Version: development version Resolution: | Keywords: -------------------------+--------------------------------------------------
Comment (by eschnett):
We can activate SystemTopology automatically, and/or require it by thorn MPI.
We can correct the affinity settings on Stampede. But what about Blue Waters, Comet, Cori, Edison, ...? For each system, and for each combination of (number of MPI processes per node, number of OpenMP threads per MPI process), we need to check that the run script sets up something useful.
In this case here, we didn't even discuss the number of MPI processes and OpenMP threads used, and we didn't check that the new "good" settings do something reasonable for other cases.
There are at least three important cases: one MPI process per node, one per socket, and one per core; and if someone experiments with under- subscribing a node (because of running out of memory), we don't silently want to do the wrong thing. The respective if statements and conditions in the run scripts can be hairy.