[Haskell-cafe] Haskell Speed Myth

[Aaron Tomb]

On Aug 29, 2008, at 9:11 AM, Isaac Gouy wrote:

> The benchmarks game always seems to demand somewhat unnatural acts and
> here's another - is there an effective way to /prevent/ ghc using
> multiple cores when multiple cores are available? Can we force ghc to
> only use one core on the quadcore machine? (Moreover can we do the  
> same
> trick for other languages?)

There is indeed. In fact, GHC-compiled programs will only use multiple  
processors if you explicitly tell them to. To make use of two  
processors, for instance, you have to pass the flags '+RTS -N2' to the  
compiled executable when you run it. This tells it to schedule its  
internal threads on two OS threads, which the OS will presumably run  
on two processors if possible.

Aaron