Ross Mellgren schrieb:
Duncan, I think you must have some magics -- on my machine the original code also takes forever. Running with +RTS -S indicates it's allocating several gig of memory or more.
Applying some bang patterns gives me ~8s for 10^8 and somewhat more than a minute for 10^9: Hi, same here, with bang patterns ~100s / 1Mb but
The C program is quite fast:
rmm@Hugo:~$ time ./circ-orig 1302219321 looks wrong to me
real 0m1.073s
cafe(0) $ time ./gauss 3141592649589764829 real 0m17.894s So my 32-bit machine is really slow ... benedikt
On Wed, 2009-01-28 at 16:42 -0800, drblanco wrote:
I do already have the number I wanted, but was wondering how this could be made faster, or even why it's so slow. This is all on GHC 6.8.3 under OS X Intel, using ghc -O2.
I'm not exactly sure what's different, but for me it works pretty well. I put back in the Int64 type signature.
For comparison, the C code below runs in <1 second.
You've got a faster machine than me :-)
I compiled both the Haskell and C versions to standalone executables with ghc/gcc -O2 and ran them with time.
C version: $ time ./circ 3141592649589764829
real 0m2.430s user 0m2.428s sys 0m0.000s
Haskell version: time ./circ2 3141592653589764829
real 0m2.753s user 0m2.756s sys 0m0.000s
Not too bad I'd say! :-)
I was using ghc-6.10 for this test. It would appear that ghc-6.8 is a bit slower, I get:
3141592653589764829
real 0m5.767s user 0m5.768s sys 0m0.000s
Now the other difference is that I'm using a 64bit machine so perhaps ghc just produces terrible code for Int64 on 32bit machines.
Duncan
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