Author: Gerd Isenberg
Date: 14:00:45 12/03/02
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Hi Miguel,
interesting serialisation approach. Soo many ways to Rome ;-)
Some thoughts:
Even if the instructions are cheap, you obviously run for every set bit through
the inner loop, where the *ps++ = r | c; instruction occurs. Also it seems the
runtime of your loops depend on the bit-positions (eg. bit 0 terminates earlier
than bit 31 if they are exclusively set in one 32bit-word).
Next point is you write terminated square arrays into memory, and you have to
traverse this arrays later, looking for the terminator, or do i miss something?
So you need a second, but of course cheaper loop.
If i look to Walters routine, so few instructions to get a bit index, i believe
this direct bitscan approach is cheaper. Also the outer control structure seems
IMHO easier and more readable, but that may be a matter of taste.
while (bb)
doSomething( bitSearchAndReset(bb) );
If i would do it in that way, your approach may preferable:
int squares[64+1];
for (int i=0; bb; ++i)
squares[i] = bitSearchAndReset(bb);
squares[i] = 0;
for (int i=0; squares[i]; ++i)
doSomething( squares[i] );
Anyway, interesting algorithm to get the square indicies, thanks for sharing.
Regards,
Gerd
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