[Haskell-cafe] Haskell vs GC'd imperative languages, threading, parallelizeability (is that a word? :-D )

[Hugh Perkins]

On 8/10/07, Donald Bruce Stewart <dons at cse.unsw.edu.au> wrote:
>
> No, STUArray s Int Bool is a bit array.
> Look at the space use. Or try replacing Bool with Word32, and see what
> happens.
>

Fair enough.  Well, the mono example in the shootout is lacking quite a few
optimizations, eg its using the builtin BitArray (slowww....), and it's not
checking for the value of the bits before writing them.  I dont quite get as
fast as your ghc version (yet ;-) ), but its within 10% on my machine, using
Microsoft C#, and staying within the rules of the shootout.

G:\dev\haskell>primeshootoutmono3
Primes up to 10240000   679461
elapsed time: 0.921875

G:\dev\haskell>primeshootoutghc
Primes up to 10240000   679461
0.8280000000000001

class NSieveBits
{
   public int nsieve(int m) {
      int[] isNotPrime = new int[((m+1) >> 5) + 1];
      int count = 0;

      int wordindex = 0;
      int bitmask = 4;
      for (int i=2; i <= m; i++)
      {
         //Console.WriteLine( i + " " + wordindex + " " + bitmask );
         if ( ( isNotPrime[wordindex] & bitmask ) == 0 )
         {
              //Console.WriteLine("prime: " + i );
            for (int k = (i << 1); k <= m; k+=i)
            {
               int _wordindex = k >> 5;
               int _bitmask = 1 << ( k & 31 );
               int _thisword = isNotPrime[_wordindex];
               if( ( _thisword & _bitmask ) == 0 )
               {
                  isNotPrime[ _wordindex ] = _thisword | _bitmask;
               }
            }
            count++;
         }
         if( bitmask == ( 1 << 31 ) )
         {
            wordindex++;
            bitmask = 1;
         }
         else
         {
            bitmask <<= 1;
         }
      }
      return count;
   }
}

It'd be more interesting to run these things in a multicore environment (16
cores would be ok, 64 would be better).  Are there any utilities out there
to do this? (vmware???)
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