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Subject: Re: The need to unmake move

Author: Angrim

Date: 09:43:39 08/20/03

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On August 19, 2003 at 20:06:58, Mathieu Pagé wrote:

>Hi,
>
>The fact:
>
>I have this question i read at some place that it is faster to unmake a move
>than to save the state of the game before moving then restoring it when we want
>to unmake the move.
>
>For the moment my engines did not implement unmake() (it is still buggy).
>
>My thougth:
>
>Since bitboard computation are slow (on 32 hardware) i think that it can be
>slower to unmake the move than to save the state. I friend of me that is lot
>better than me at optimizing code also think that.
>
>My questions:
>
>Are you all using unmake() function or there is some of you that found that
>saving the state is better ?
>
>In the case that unmake is better. by wich factor ?
>
>Thanks for your help.
>
>Mathieu Pagé

unmake is slower for me, by roughly 2:1  I have a relatively small board
structure, so it is usually all in cache and the extra computations and
branches in unmake are more expensive than copying a few cache lines worth
of data.
for an engine with a large board structure, I expect the opposite result.

Angrim



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