On Wed, Apr 23, 2008 at 5:01 PM, Tillmann Vogt <Tillmann.Vogt@rwth-aachen.de> wrote:

Hi,

I am currently experimenting with parallelizing C-programs. I have therefore written a matrix vector multiplication example that needs 13 seconds to run (5 seconds with OpenMP). Because I like Haskell I did the same in this language, but it takes about 134 seconds. Why is it so slow? Does someone have an idea?

Yes, in the C version you use unboxed arrays, in the Haskell version you use a linked list of linked lists. Naturally the latter will take up more space, require more work to index, and will thrash the cache quite a bit.