#774: hack to unfix OpenMP threads from cores on Cray machines -----------------------+---------------------------------------------------- Reporter: rhaas | Owner: eschnett Type: task | Status: closed Priority: optional | Milestone: Component: Carpet | Version: Resolution: fixed | Keywords: hack -----------------------+---------------------------------------------------- Changes (by eschnett):
* status: review => closed * resolution: => fixed
Comment:
I believe that the process affinity is inherited across exec. That means that one can write a wrapper that first sets the affinity, and then execs the Cactus executable.
In fact, such a program already exists; it is called "numactl". I just tried on Hopper -- it does not run because it cannot find certain libraries. Maybe rebuilding numactl would already correct this problem?
You would use it similar to "aprun -bla numactl -bla cactus_sim -bla my.par".
I applied your patch with certain modifications. For example, instead of calling it "Cray hack" I view this as a generic feature that may also be useful elsewhere.