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Subject: Re: significant math

Author: Robert Hyatt

Date: 08:15:17 11/20/02

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On November 20, 2002 at 11:07:32, Sune Fischer wrote:

>On November 20, 2002 at 10:57:01, Robert Hyatt wrote:
>
>>On November 20, 2002 at 05:44:10, Sune Fischer wrote:
>>
>>>On November 20, 2002 at 05:37:43, Steffan Westcott wrote:
>>>
>>>>On November 20, 2002 at 05:05:25, Sune Fischer wrote:
>>>>
>>>>> I believe that "move for move" 0x88 is faster because you don't have to do
>>>>> that extra bit scan to get the square
>>>>
>>>>Which square are you referring to? Source square? Destination square? I may be
>>>>able to help you...
>>>
>>>With bitboards (as I'm sure you know) you need a piece of assembler using bsf,
>>>then you need to clear the bit afterwards. This is not needed with 0x88.
>>>
>>>ie:
>>>    while (padvances2) {
>>>      to=FirstOne(padvances2);
>>>      *move++=(to+16)|(to<<6)|(pawn<<12);
>>>      Clear(to,padvances2);
>>>    }
>>>
>>
>>
>>
>>Wrong idea however.  Most of the move generations done are for captures.  0x88
>>can't keep up with bitmaps there, because bitmaps generate _only_ capture moves,
>>while 0x88 walks down each rank/file/diagonal skipping empty squares.
>
>Yep, wasn't that what I said??

Sorry.  I didn't address that to the "right person"...  :)  an errant "back" and
I was posting
at the wrong place.  Yes, I believe you did say that...  I was trying to respond
to the same
thing you were responding too, but didn't quite make it. :)


>
>>that is one of the strengths of bitmaps.  finding a bit is quick.  Clearing it
>>takes one
>>cycle.  not very expensive.
>
>I think that was my point exactly.
>
>-S.



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