On 7/15/07, Donald Bruce Stewart <[EMAIL PROTECTED]> wrote:
[snip] unsafeWrite[snip]
[snip]unsafeRead[snip]
Hi Donald, the idea is to use this for operational code, so avoiding unsafe
operations is preferable ;-) You'll note that the C# version is not using
unsafe operations, although to be fair that's because they worked out slower
than the safe version ;-)
Also, the whole algorithm is bound to the IO Monad, which is something I'd
like to avoid if possible, since my entire interest in Haskell stems from
the possibilites of running programs easily on 1 megacore processors in the
future.
Initial compilation gives an error:
PrimeDonald.hs:18:3: Illegal bang-pattern (use -fbang-patterns)
Ok, I'm ok with compiler patches, that's half the point of such a
competition really, to encourage compiler optimization.
Anyway, congrats you got nearly as fast as C#!
J:\dev\haskell>ghc -fglasgow-exts -fbang-patterns -O2 -o PrimeDonald.exePrimeDo
nald.hs
J:\dev\haskell>primedonald
number of primes: 664579
Elapsed time: 0.797
J:\dev\test\testperf>erase primecs.exe
J:\dev\test\testperf>gmcs primecs.cs
J:\dev\test\testperf>mono primecs.exe
number of primes: 664579
elapsed time: 0,719
J:\dev\test\testperf>erase primecs.exe
J:\dev\test\testperf>csc /nologo primecs.cs
J:\dev\test\testperf>primecs
number of primes: 664579
elapsed time: 0,6875
Here is the Haskell code:
module Main
where
import Data.Array.IO
import Data.Array.Base
import System
import System.Time
import System.Locale
calculateNumberOfPrimes n = do
a <- newArray (2,n) True :: IO (IOUArray Int Bool) -- an array of
Bool
go a n 2 0
go !a !m !n !c
| n == m = return c
| otherwise = do
e <- unsafeRead a n
if e
then let loop !j
| j <= m = unsafeWrite a j False >> loop
(j+n)
| otherwise = go a m (n+1) (c+1)
in loop (n+n)
else go a m (n+1) c
gettime :: IO ClockTime
gettime = getClockTime
main = do starttime <- gettime
numberOfPrimes <- (calculateNumberOfPrimes 10000000)
putStrLn( "number of primes: " ++ show( numberOfPrimes ) )
endtime <- gettime
let timediff = diffClockTimes endtime starttime
let secondsfloat = realToFrac( tdSec timediff ) +
realToFrac(tdPicosec timediff) / 1000000000000
putStrLn( "Elapsed time: " ++ show(secondsfloat) )
return ()
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