I think you need to specify how many cores to use when you call your ./Main program. Something like "./Main -random 4096 4096 -random 4096 4096 +RTS -N4" (given that you have 4 cores). You'll also need to add -rtsopts when you're compiling your code with ghc.

On Thu, Nov 7, 2013 at 1:40 AM, Alexander Herz <alexander.herz@mytum.de> wrote:

Hi,

I'm new to haskell and I tried to reproduce the perfomance values from the paper "Regular, Shape-polymorphic, Parallel Arrays in Haskell".

I modified the repa-mmult example from the repa-example package to use the mmultP from Data.Array.Repa.Algorithms.Matrix.

Then I compile it with "ghc -threaded -fglasgow-exts -O Main.hs" but running it with two large matrices :

"./Main -random 4096 4096 -random 4096 4096" I can see that only one of my 4 cpus is utilized.

What am I doing wrong?

Note: The unmodified repa-example also does not run in parallel.

Thx,
Alex
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