OK, if somebody wants to speculate (and if it even makes sense for
such a microbenchmark) here are some more data.
Except different OS and C++ compiler also processor is different.
On my side it was AMD Athlon 64 X2 4800+ (2.4GHz, 2x1MiB L2 cache
non-shared; C&Q was not switched off during the test). The system has
2GiB RAM. The C++ version had working set about 1.7 MiB, ghc version
had it about 2 times bigger.
Peter.
Dusan Kolar wrote:
Hello all,
just to compare the stuff, I get quite other results being on other OS.
Thus, the result of C++ compiler may not be that interesting as I do not
have the one presented below.
My machine:
Linux 2.6.23-ARCH #1 SMP PREEMPT Mon Oct 22 12:50:26 CEST 2007 x86_64
Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz GenuineIntel GNU/Linux
Compilers:
g++ --version
g++ (GCC) 4.2.2
Copyright (C) 2007 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.
ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.6.1
Measurement:
compiled with ghc -O2
time ./mainInteger
real 0m4.866s
user 0m4.843s
sys 0m0.020s
compiled with ghc -O2
time ./mainInt64
real 0m2.213s
user 0m2.210s
sys 0m0.003s
compiled with ghc -O2
time ./mainInt
real 0m1.149s
user 0m1.143s
sys 0m0.003s
compiled with g++ -O3
time ./mainC
real 0m0.271s
user 0m0.270s
sys 0m0.000s
I don't know what is the reason, but the difference between Int, Int64
and Integer is not that dramatic as in example below, nevertheless, the
difference between GHC and GNU C++ is very bad.... :-\
Dusan
Peter Hercek wrote:
Derek Elkins wrote:
Try with rem instead of mod.
(What the heck is with bottom?)
The bottom was there by error and I was lazy to redo
the tests so I rather posted exactly what I was
doing. I do not know the compiler that good to be
absolutely sure it cannot have impact on result
... so I rather did not doctor what I did :-)
Ok, rem did help quite a bit. Any comments why it is so?
Here are summary of results for those interested. I run
all the tests once again. Haskell was about 13% slower
than C++.
MS cl.exe options: /Ox /G7 /MD
ghc options: -O2
C++ version: 1.000; 0.984; 0.984
Haskell version specialized to Int: 1.125; 1.125; 1.109
Haskell version specialized to Integer: 8.781; 8.813; 8.813
Haskell version specialized to Int64: 9.781; 9.766; 9.831
The code:
% cat b.hs
module Main (divisors, perfect, main) where
import Data.Int
divisors :: Int -> [Int]
divisors i = [j | j<-[1..i-1], i `rem` j == 0]
perfect :: [Int]
perfect = [i | i<-[1..10000], i == sum (divisors i)]
main = print perfect
% cat b.cpp
#include <iostream>
using namespace std;
int main() {
for (int i = 1; i <= 10000; i++) {
int sum = 0;
for (int j = 1; j < i; j++)
if (i % j == 0)
sum += j;
if (sum == i)
cout << i << " ";
}
return 0;
}
%
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