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

Sebastian Sylvan sebastian.sylvan at gmail.com
Wed Apr 23 12:24:20 EDT 2008

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

> 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.
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