[Haskell-cafe] Re: Very fast loops. Now!

[David Roundy]

On Mon, Feb 12, 2007 at 02:25:21PM -0800, Bryan O'Sullivan wrote:
> David Roundy wrote:
> >I'm rather curious (if you're sill interested) how this'll be affected by
> >the removal of the division from the inner loop. e.g.
> >
> >    go :: Double -> Double -> Int -> IO ()
> >    go !x !y !i
> >        | i == 1000000000 = printf "%.6f\n" (x+y)
> >        | otherwise       = go (x*y*(1.0/3)) (x*9) (i+1)
> >
> >
> >    for (; i<1000000000; i++) {
> >        x = x*y*(1.0/3.0);
> >        y = x*9.0;
> >    }
> 
> GCC will do the transformation itself if you use -ffast-math.  It 
> requires the flag as the results aren't exactly numerically equivalent.

Ah, okay.  Never mind, then.
-- 
David Roundy
Department of Physics
Oregon State University