Author: Gian-Carlo Pascutto
Date: 14:27:43 06/25/02
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On June 25, 2002 at 17:04:43, Robert Hyatt wrote: >What about more commonly: Is the black pawn on e6 passed. Now you have >to check 12 squares... d2/e2/f2, d3/e3/f3, d4/e4/f4, d5/e5/f5. > >Bitmaps: two loads one and. No compare. Just a branch not zero. > >traditional... 12 loads 12 compares. More like...1 load 1 compare. >Asking simple questions with bitmaps is not so good on 32 bit machines. On >a 64 bit machine, your above becomes > >1 load. 1 mask create (set 1 bit and shift, two instructions, done in the >"shadow" of the load, then one compare. > >On a 64 bit machine, they are equally fast for the simple operation. For >the second case, the 64 bit machine is an easy winner. At 32 bits, the nonbitboard approach wins out. At 64 bits, it's still 'better' (not slower and uses less functional units). I'm not saying there aren't things that are faster with bitboards, I'm just saying there certainly are things that are faster without. -- GCP
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