[Haskell-cafe] Haskell Speed Myth

Aaron Tomb atomb at galois.com
Fri Aug 29 12:29:44 EDT 2008

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.


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