GCC 4.x gets a pass on this test. :)
You can do (much) better than that, of course.
But it's what I'd expect without going over board.
-- Lennart
On Feb 10, 2007, at 16:45 , Donald Bruce Stewart wrote:
dons:
The following C program was described on #haskell
#include <stdio.h>
int main()
{
double x = 1.0/3.0;
double y = 3.0;
int i = 1;
for (; i<=1000000000; i++) {
x = x*y/3.0;
y = x*9.0;
}
printf("%f\n", x+y);
}
Which was translated to the following Haskell:
{-# OPTIONS -fexcess-precision #-}
import Text.Printf
main = go (1/3) 3 1
go :: Double -> Double -> Int -> IO ()
go !x !y !i
| i == 1000000000 = printf "%f\n" (x+y)
| otherwise = go (x*y/3) (x*9) (i+1)
To everyone's surprise, GHC 6.6 beats GCC (3.3.5) here, at least
the two test machines:
$ ghc -O -fexcess-precision -fbang-patterns -optc-O3 -optc-
ffast-math -optc-mfpmath=sse -optc-msse2 A.hs -o a
$ time ./a
3.333333
./a 0.96s user 0.01s system 99% cpu 0.969 total
^^^^^
Versus gcc 3.3.5:
$ gcc -O3 -ffast-math -mfpmath=sse -msse2 -std=c99 t.c -o c_loop
$ time ./c_loop
3.333333
./c_loop 1.01s user 0.01s system 97% cpu 1.046 total
^^^^^
Note that newer gcc's will statically compute that loop. Note also
that
-fexcess-precision must currently be provided as a pragma only.
I declare GHC Haskell numerics (with -fexcess-precision) not so
shabby!
GCC 4.x seems to do a much better job, turning the inner loop into:
.L2:
mulsd %xmm3, %xmm0
mulsd %xmm1, %xmm0
movapd %xmm0, %xmm1
mulsd %xmm2, %xmm1
addl $1, %eax
cmpl $100000001, %eax
jne .L2
-- Don
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
