[Haskell-cafe] Re: [Haskell] Matrix multiplication

[Henning Thielemann]

On Wed, 23 Apr 2008, Sebastian Sylvan wrote:

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

For full speed matrix computations see
   http://alberrto.googlepages.com/gslhaskell