[Haskell-cafe] Importing Data.Char speeds up ghc around 70%

Stefan O'Rear stefanor at cox.net
Sat Dec 22 13:28:38 EST 2007

On Sat, Dec 22, 2007 at 06:00:29PM +0000, Joost Behrends wrote:
> Hi,
> while still working on optimizing (naively programmed) primefactors i watched a
> very strange behavior of ghc. The last version below takes 2.34 minutes on my
> system for computing 2^61+1 = 3*768614,336404,564651. Importing Data.Char
> without anywhere using it reduces this time to 1.34 minute - a remarkable speed
> up. System is WindowsXP on 2.2GHZ Intel, 512MB Ram.
> I give the complete code here - hopefully all tabs are (4) blanks. Can this be
> reproduced ? I compile just with --make -O2.

If you can reproduce it on your machine (rm <executable> *.o *.hi
between tests for maximum reliability), it's definitely a bug.


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