[Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
The program seems to take around 6 seconds on my linux-box, while the c version goes for 0.06 sekcond. That is really some regression bug :-) Anyone with a more recent version thatn 7.4.1? Felix Fra: Johan Tibell johan.tib...@gmail.com Til: Fixie Fixie fixie.fi...@rocketmail.com Kopi: Haskell cafe haskell-cafe@haskell.org Sendt: Torsdag, 29. november 2012 21.50 Emne: Re: [Haskell-cafe] To my boss: The code is cool, but it is about 100 times slower than the old one... Ack, it seems like you're running into one of these bugs (all now fixed, but I don't know in which GHC version): http://hackage.haskell.org/trac/ghc/search?q=doubleFromInteger___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
That's really an argument for upgrading to 7.4.2 :-) Another reason for doing things with haskell is this mailing list. Thanks! Felix Fra: Johan Tibell johan.tib...@gmail.com Til: Fixie Fixie fixie.fi...@rocketmail.com Kopi: Haskell cafe haskell-cafe@haskell.org Sendt: Torsdag, 29. november 2012 22.06 Emne: Re: [Haskell-cafe] To my boss: The code is cool, but it is about 100 times slower than the old one... On Thu, Nov 29, 2012 at 1:00 PM, Fixie Fixie fixie.fi...@rocketmail.com wrote: The program seems to take around 6 seconds on my linux-box, while the c version goes for 0.06 sekcond. That is really some regression bug :-) Anyone with a more recent version thatn 7.4.1? On 7.4.2: $ time ./c_test ... real 0m0.145s user 0m0.040s sys 0m0.003s $ time ./Test ... real 0m0.234s user 0m0.220s sys 0m0.006s Both compiled with -O2.___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Donnerstag, 29. November 2012, 21:00:36, Fixie Fixie wrote: The program seems to take around 6 seconds on my linux-box, while the c version goes for 0.06 sekcond. That is really some regression bug :-) Anyone with a more recent version thatn 7.4.1? I don't even have a problem with 7.4.1: $ for ghc in $GHCS; do echo $ghc; time ./hskahan-$ghc /dev/null; done; 7.0.4 real0m0.217s user0m0.214s sys 0m0.002s 7.2.1 real0m0.197s user0m0.194s sys 0m0.002s 7.2.2 real0m0.187s user0m0.187s sys 0m0.000s 7.4.1 real0m0.253s user0m0.249s sys 0m0.003s 7.4.2 real0m0.250s user0m0.247s sys 0m0.002s 7.6.1 real0m0.224s user0m0.221s sys 0m0.002s $ time ./ckahan /dev/null real0m0.102s user0m0.079s sys 0m0.022s We have an unpleasant regression in comparison to 7.2.* and the 7.4.* were slower than 7.6.1 is, but it's all okay here (not that it wouldn't be nice to have it faster still). Are you on a 32-bit system? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Thu, Nov 29, 2012 at 1:32 PM, Daniel Fischer
daniel.is.fisc...@googlemail.com wrote:
We have an unpleasant regression in comparison to 7.2.* and the 7.4.* were
slower than 7.6.1 is, but it's all okay here (not that it wouldn't be nice to
have it faster still).
Are you on a 32-bit system?
This version works around the Word-Double conversion bug and shows
good performance:
(Always compile with -Wall, it tells you if some arguments are
defaulted to slow Integers, instead of fast Ints.)
{-# LANGUAGE CPP, BangPatterns, MagicHash #-}
module Main (main) where
#define VDIM 100
#define VNUM 10
import Control.Monad.ST
import Data.Array.Base
import Data.Array.ST
import Data.Bits
import GHC.Word
import GHC.Exts
prng :: Word - Word
prng w = w'
where
w1 = w `xor` (w `shiftL` 13)
w2 = w1 `xor` (w1 `shiftR` 7)
w' = w2 `xor` (w2 `shiftL` 17)
type Vec s = STUArray s Int Double
kahan :: Vec s - Vec s - ST s ()
kahan s c = do
let inner !w j
| j VDIM = do
cj - unsafeRead c j
sj - unsafeRead s j
let y = word2Double w - cj
t = sj + y
w' = prng w
unsafeWrite c j ((t-sj)-y)
unsafeWrite s j t
inner w' (j+1)
| otherwise = return ()
outer i | i VNUM = inner (fromIntegral i) 0 outer (i + 1)
| otherwise = return ()
outer (0 :: Int)
calc :: ST s (Vec s)
calc = do
s - newArray (0,VDIM-1) 0
c - newArray (0,VDIM-1) 0
kahan s c
return s
main :: IO ()
main = print . elems $ runSTUArray calc
word2Double :: Word - Double
word2Double (W# w) = D# (int2Double# (word2Int# w))
On my (64-bit) machine the Haskell and C versions are on par.
-- Johan
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Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Thu, Nov 29, 2012 at 1:40 PM, Johan Tibell johan.tib...@gmail.com wrote: This version works around the Word-Double conversion bug and shows good performance: I'd also like to point out that I've removed lots of bang patterns that weren't needed. This program runs fine without any bang patterns (but I've kept the one that can possibly have any performance implication at all). -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Donnerstag, 29. November 2012, 13:40:42, Johan Tibell wrote: word2Double :: Word - Double word2Double (W# w) = D# (int2Double# (word2Int# w)) On my (64-bit) machine the Haskell and C versions are on par. Yes, but the result is very different. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Donnerstag, 29. November 2012, 13:40:42, Johan Tibell wrote: word2Double :: Word - Double word2Double (W# w) = D# (int2Double# (word2Int# w)) On my (64-bit) machine the Haskell and C versions are on par. On my box, the Haskell is even faster then, but, as said, the result is incorrect With correction :: Double correction = 2 * int2Double minBound word2Double :: Word - Double word2Double w = case fromIntegral w of i | i 0 - int2Double i - correction | otherwise - int2Double i I get real0m0.078s user0m0.077s sys 0m0.001s with correct results. Okay, we **need** a better Word - Double etc. conversion. We could start with the above, that seems not too shabby. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Vedr: To my boss: The code is cool, but it is about 100 times slower than the old one...
On Thu, Nov 29, 2012 at 2:02 PM, Johan Tibell johan.tib...@gmail.com wrote: On Thu, Nov 29, 2012 at 2:01 PM, Daniel Fischer daniel.is.fisc...@googlemail.com wrote: On Donnerstag, 29. November 2012, 13:40:42, Johan Tibell wrote: word2Double :: Word - Double word2Double (W# w) = D# (int2Double# (word2Int# w)) On my (64-bit) machine the Haskell and C versions are on par. Yes, but the result is very different. Doh, I guess I didn't look at the output carefully enough. One obvious error is that the C code has one loop go from 1..n where I just naively assumed all loops go from 0..n-1. This fixes that: outer i | i = VNUM = inner (fromIntegral i) 0 outer (i + 1) | otherwise = return () outer (1 :: Int) Perhaps the other issue is that word2Double (W# w) = D# (int2Double# (word2Int# w)) is possibly the wrong way and we need a word2Double#. -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
