For such operations, Julia calls out to OpenBLAS; while OpenBLAS is terrific, the number of threads has been a bit of a sore point.
https://github.com/xianyi/OpenBLAS/issues/103 --Tim On Thursday, March 27, 2014 12:15:04 PM Carlos Stein wrote: > Hi all, > > I'm getting started with Julia, looks great. > > I was testing the performance for a simple array product *(A*v)* and it > depended if *v* is a vector or an array. The matrix version > > A = randn(400,4000) > > v = randn(4000,1) > y = A*v > > > used one core, while the vector version > > > A = randn(400,4000) > > v = randn(4000) > y = A*v > > > used all 16 cores and was 10x faster. > > Is there an easy way to know and choose how many cores will be used for a > given operation? > > Thanks! Carlos
