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Subject: Re: How much better is phased move generation/ordering?

Author: Pham Hong Nguyen

Date: 19:48:52 08/26/04

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On August 26, 2004 at 16:25:07, Lance Perkins wrote:

>After seeing the posted NextMove code, I wonder how much better this is than
>simply generating all the moves and then sorting them in one go.
>
>This code is a little to complex and tool long for my liking, but if it offers a
>very significant gain, maybe I should give it a second look.


If you try it, you may change your mind. For chess, imagination may be quite
different from practice :)

The gain depends much on your board representation. You may notice that the
bitboard could generate the capture moves faster than the non-capture ones. That
is why Crafty generates moves in phases in hope to avoid genarating non-capture
moves. But if your board is an array style (like mine), where both capture and
non-capture moves could be generated by the same speed and the combination of
them can save time in many cases, phase generation gains almost nothing (or
negative thing).

BTW, you are talking about a gain of 0-3% (for any kinds of board
representations), it is not very significant gain as you wish.

Pham

>
>I can immagine that when one gets a cutoff, the rest of the moves don't have to
>be generated (captures vs non-captures). However, in leaf nodes, one is very
>likely to generated all the moves anyway.
>
>Has anyone compared these?



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