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Subject: Re: PVS and aspiration windows

Author: José Carlos

Date: 16:32:02 08/06/04

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On August 06, 2004 at 08:44:32, Tord Romstad wrote:

>A basic question from a PVS newbie:
>
>How much of an improvement should I expect to see when I introduce aspiration
>windows in a PVS search?  When using an aspiration window of +- 0.5 pawns,
>I don't see any improvement at all compared to a window of +- INFINITY.  In
>most positions, the node counts differ by just a couple of % (and the version
>with aspiration is not always the fastest).
>
>Is this what I should expect, or should I start looking for a bug?
>
>Tord

  I've always had aspiration and every try to remove it has been bad for me. I
guess, considering most other results, that I must have something incorrectly
implemented regarding mate scores and hash table, but I've never found exactly
what I do wrong.
  My aspiration is also a bit sophisticated (!= good). I adjust the size of the
window dinamically, either the first search and the researches (for fail high or
fail low). I try to get rid of mates unless there's no other chance. For
example, in case of a very big fail high, instead of setting beta = +INFINITY, I
first try beta = bigger than any score except mate in max.
  It works for me, but as I said, I believe I have a problem elsewhere.

  José C.



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