On Mon, 18 Feb 2019 16:12:41 +0100 zimoun <[email protected]> wrote:
> Dear, > > I am not sure to understand if it is expected or not. > > Let install R, guix package -i r, and then run the small script: > > > N <- 9000;A <- array(0.1, dim=c(N,N));B <- array(0.1, dim=c(N,N)) > > dim(B %*% A) > > Monitoring with htop, only 8 of my 16 cores are used. Why ? > And if I have more, then again only 8 cores will be used. OpenBLAS will use as many threads as the OpenMP runtime will give it, which is by default one per CPU. I think this default does not take into account hyperthreads, which htop shows as a separate "cpu". You can set the "OMP_NUM_THREADS" environment variable and OpenBLAS should pick it up. I don't know whether R does anything for setting OpenMP runtime settings. Hope that helps, `~Eric
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