Don Stewart
Can you start by retrying with flags from the spectral-norm benchmark:
http://shootout.alioth.debian.org/gp4/benchmark.php?test=spectralnorm&lang=ghc&id=0
The interaction with gcc here is quite important, so forcing -fvia-C will matter.
Clearly things has been changed, since the release of ghc-6.8.1. I tried them with my laptop, and here are the results of N=3000. C++ g++ ======= real 0m4.553s user 0m4.551s sys 0m0.002s changed one option: -march=nocona Haskell GHC =========== real 0m34.392s user 0m34.316s sys 0m0.074s I used `unsafePerformIO' with `INLINE', because I don't know where `inlinePerformIO' is now. And also the `-optc-march' is changed to `nocona'. Haskell GHC #2 ============== real 0m20.069s user 0m20.052s sys 0m0.017s The same label `Haskell GHC #2' on that web page. This is the one without any optimisation. And it out performs the previous heavily optimised one. Is it because I used `unsafePerformIO' instead of the original `inlinePerformIO'? `-optc-march' is also changed to `nocona'. Is it only my laptop, or ghc-6.8.1 is indeed much faster than 6.6.1 and the internal has changed so much that the old optimisation no longer works? $ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.8.1 $ gcc --version gcc (GCC) 4.1.2 (Gentoo 4.1.2 p1.0.2) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Intel(R) Core(TM)2 Duo CPU T7700 @ 2.40GHz Xiao-Yong -- c/* __o/* <\ * (__ */\ <