On 12/04/2011, at 11:50 PM, Wilfried Kirschenmann wrote:
surprisingly, when removing the R.force from the code you attached, performances are better (speed-up=2). I suppose but I am not sure that this allow for loop fusions beetween the R.map ant the R.sum.
I use ghc 7.0.3, Repa 2.0.0.3 and LLVM 2.9.
By the end, the performances with this new version (0.48s) is 15x better than my original version (6.9s) However, the equivalent sequential C code is still 15x better (0.034s).
This may indeed be explained by the fact that all computations are performed inside the R.sum.
Yeah, the Repa fold and sum functions just use the equivalent Data.Vector ones. They're not parallelised and I haven't looked at the generated code. I'll add a ticket to the trac to fix these, but won't have time to work on it myself in the near future. Ben.