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Subject: Re: mate threat extension/null move

Author: Andrew Platt

Date: 10:20:54 09/26/04

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On September 25, 2004 at 23:56:39, Rick Bischoff wrote:

>But this is what Bob Hyatt does in crafty-- quote verbatim from search.c:
>      if (depth - null_depth >= INCPLY)
>        value =
>            -Search(tree, -beta, 1 - beta, Flip(wtm), depth - null_depth,
>            ply + 1, NO_NULL, 0);
>      else
>        value = -Quiesce(tree, -beta, 1 - beta, Flip(wtm), ply + 1);
>    ... snip ...
>    if (value >= beta) {
>        HashStore(tree, ply, depth, wtm, LOWER, value, mate_threat);
>        return (value);

This just shows that Crafty does *not* do what the code extract you posted since
that returned beta when value >= beta. Crafty returns value, the other returns
beta. In terms of cutoff there's no difference but it means that you can't use
the score for anything other than cutoff purposes.

Now, the full code your engine may be returning value elsewhere but my guess is
that if you return beta (or alpha) in one place, you do it in others too.


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