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

Joost Behrends webmaster at h-labahn.de
Sat Dec 22 23:40:24 EST 2007

Neil Mitchell <ndmitchell <at> gmail.com> writes:
> If it can be reproduced on anyones machine, it is a bug. If you can
> bundle up two programs which don't read from stdin (i.e. no getLine
> calls) or the standard arguments (i.e. getArgs) which differ only by
> the Data.Char import, and have massive speed difiference, then report
> a bug.
> You should probably also give your GHC versions and platforms etc.

Thanks for your attention too !

Now i tried a version without input (just computing the primefactors of the
constant 2^61+1, what it did correctly in spite of its bugginess). And it
didn't have the Data.Char bug (and Data.List bug) too.

As my original code hasn't on Linux also it seems.

Thus it  happens only in an exotic configuration. Windows will stay exotic
in the Haskell community. Before should noone
has reproduced it at least on Windows (XPpro SP2 is my version), i will do 
nothing more.

The hardware is Intel Celeron 2.2GHZ, 512 MB Ram. ghc 6.8.1 lives on
D:\\Programme (not on the system drive C:, which poses problems to Cabal, 
told aside). I just made the standard installation (do not remember, whether
by unzipping alone or there was an MSI) not touching anything, of course. 
I was happy about no autoconf (which i see in the category of desasters like
EMM386 for MS-DOS).

But something is strange: ghci doesn't accept
qualified imports. It produces a parse error. That seems a bug to me, because
my ghci accepts "import (any module)" nevertheless. But i see it as a minor
bug - the compiler is much more important.

Happy days, Joost

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