int n;

scanf("%d", &n);

for(i=0; i<n;i++)

{

sum += i;

}

GCC need 100 milliseconds on my 3.0GHz new Xeon with loop unrolling enabled.

Without loop unrolling GCC needs about 635ms

Visual C++ does it in 577 ms, generating the following code:

loop: add rbx,rax

inc rax

cmp rax,rcx

jl loop

GHC with -O2 -fvia-c (the fastest I could make it) needs

13075 for the naive sum

2100 ms with sum0

2018 ms using the stream-fusion

Interesting to see that the stream-fusion was slower when not doing -fvia-c (more than twice as slow with -O)

So GHC is about 3 to 4 times slower as Visual C++ / GCC without loop unrolling, which is not too bad since GHC does not perform register optimization and loop unrolling yet no?

On Fri, Feb 20, 2009 at 3:44 PM, Achim Schneider <barsoap@web.de> wrote:

Bulat Ziganshin <bulat.ziganshin@gmail.com> wrote:

> execution times:
> sum:
> ghc 6.6.1 -O2 : 12.433 secs
> ghc 6.10.1 -O2 : 12.792 secs
> sum-fast:
> ghc 6.6.1 -O2 : 1.919 secs
> ghc 6.10.1 -O2 : 1.856 secs
> ghc 6.10.1 -O2 -fvia-C : 1.966 secs
> C++:
> gcc 3.4.5 -O3 -funroll-loops: 0.062 secs
>

Nice! Now we know that gcc can calculate faster than Haskell can
calculate and print. Next time, use exitWith, please.

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