Le mardi 04 février 2014 à 23:17 +0100, Julian Taylor a écrit : > There are well known issues with the gnu openmp variant of openblas in > respect to forks of applications. > This causes numerous issues especially in the python world where forking > is very common. > see e.g. https://github.com/xianyi/OpenBLAS/issues/294 > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=737675 > > As openblas is integrated into Debians blas alternative system it needs > to be rock solid compared to ATLAS and netlib blas. > This is known not to be the case for openmp openblas but somewhat > working with pthreads. > As my viewpoint is very narrow coming from python I want to ask if there > are known and ideally reproducable cases where pthread openblas breaks > applications but openmp openblas does not?
Please find attached an example of such a breakage, using parallelisation in R. The example is run simply with: R --vanilla < foo.R On sid, with openblas 0.2.8-3 (OpenMP), the program runs and reports 8 condition numbers. On sid but with openblas 0.2.8-2 (pthreads), the program hangs. -- .''`. Sébastien Villemot : :' : Debian Developer `. `' http://www.dynare.org/sebastien `- GPG Key: 4096R/381A7594
library(parallel)
num.cores <- 4
f <- function(x)
{
n <- 40
A <- replicate(n, rnorm(n))
B <- replicate(n, rnorm(n))
rcond(A %*% B)
}
z <- 1:8
mclapply(z, f, mc.cores = num.cores)
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