[Haskell-cafe] Haskell performance question

[Stefan O'Rear]

On Thu, Nov 08, 2007 at 07:57:23PM +0100, Thomas Schilling wrote:
> 
> $ ghc --make -O2 ghc-bench.hs
> 
> and got:
> 
> $ time ./ghc-bench 
> 2.0e7
> 
> real    0m0.714s
> user    0m0.576s
> sys     0m0.132s
> 
> $ time ./ghcbC 
> 20000000.000000
> 
> real    0m0.305s
> user    0m0.164s
> sys     0m0.132s
> 
> This is on a first-gen Macbook running Ubuntu.  1GB RAM.  1.83Ghz Core
> Duo
> 
> $ ghc --version
> The Glorious Glasgow Haskell Compilation System, version 6.8.0.20071019
> 
> $ gcc --version
> gcc (GCC) 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
> 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.
> 
> 
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> $ gcc -O3 ghc-bench.c -o ghcbC
> ghc-bench.c: In function ‘main’:
> ghc-bench.c:16: warning: incompatible implicit declaration of built-in
> function ‘printf’

-O3 is worse than -O0, DO NOT USE IT.

I reported the bug several months ago.  In the meantime, use -O2.

(there are no high optimizations, it's just that the option parser
misparses -O3)

Stefan
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