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Subject: Re: Bitboards and Quick Killer

Author: Tom Kerrigan

Date: 17:45:26 08/15/00

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On August 15, 2000 at 19:56:37, Brian Richardson wrote:

>On August 15, 2000 at 18:37:44, Larry Griffiths wrote:
>
>>On August 15, 2000 at 17:14:20, Brian Richardson wrote:
>>
>>>I would think you would want to try the killer moves before even generating
>>>captures and non-captures (assuming you already have the killer move, of
>>>course).  Then just keep it simple with a MVV/LVA move ordering, which will
>>>place captures before non-captures (count pawn promotion as a capture too).
>>>Later do the same with hash moves first, then killers, then generate and so on.
>>>Each program uses a different set of algorithims, and you will just have to
>>>experiment with your mix.
>>>
>>>Brian
>>
>>This is more along what I am thinking.  I still must generate the moves for the
>>killer piece to see if it is still a valid move.  Pawns moves are generated
>>en-mass because of my bitboards so if the killer piece is a pawn, then all pawn
>>captures or pawn moves have to be generated in one fell swoop.
>>
>>Larry.
>
>
>Rather than "generating" moves for the killers, try a quick is it still legal
>routine.
>
>Regarding Tom's post:  I cannot speak for a lot of programs, but at least for
>Tinker and Crafty, doing killers before captures seems to work better.

I'm not familiar with Crafty's source, but I did a quick search for "killer" and
found the following consecutive comments:

/*
 ----------------------------------------------------------
|                                                          |
|   try the captures moves, which are in order based on    |
|   the expected gain of material.  captures that lose     |
|   material have been excluded from this phase.           |
|                                                          |
 ----------------------------------------------------------
*/
...
/*
 ----------------------------------------------------------
|                                                          |
|   now, try the killer moves.  this phase tries the two   |
|   killers for the current ply without generating moves,  |
|   which saves time if a cutoff occurs.                   |
|                                                          |
 ----------------------------------------------------------
*/

It appears that captures before killers also works for Bob.

-Tom



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