Hi, In order to do a performance comparison beetween different approaches for our application, I make different implementation of a simple example (computing the norm of a vector expression. I rely on Repa to do this. However, when I tried to build the parallel version (-threaded -fvectorise -rtsopts), I got an error specifying that dph-par was not available. Indeed, It wasn't. As explained on the dph webpage, I installed a developpment version of ghc (ghc-7.1.20110331). However, when I try to build my application, I get the folowing error: user error (Pattern match failure in do expression at compiler/vectorise/Vectorise/Monad.hs:57:10-20) My source code is attached and compiled with the following line: ghc haskell.hs -O3 -XBangPatterns -msse2 -fforce-recomp -rtsopts -threaded -fvectorise So my question is : is the problem concerning the pattern matching known ? If yes, is there a workaround ? is there an other version of dph that would work with Repa ? Thank you ! ----- Wilfried Kirschenmann "An expert is a person who has made all the mistakes that can be made in a very narrow field."* *Niels Bohr - *Danish physicist (1885 - 1962)*