On Wed, Apr 23, 2008 at 05:24:20PM +0100, Sebastian Sylvan wrote: > On Wed, Apr 23, 2008 at 5:01 PM, Tillmann Vogt <[EMAIL PROTECTED]> > 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.
In fact, I'm impressed that Haskell can come within a factor of 10, given that it's using such a challenging data type! (I wonder if this may be due to inefficiencies in the C code, although I haven't looked at it.) -- David Roundy Department of Physics Oregon State University _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
