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Subject: Re: Futility @ 1/Extended Futility @ 2/Limited Razoring @ 3 = % node reduce?

Author: Jeremiah Penery

Date: 18:11:47 10/19/04

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On October 19, 2004 at 19:51:17, Stuart Cracraft wrote:

>On October 19, 2004 at 16:34:32, GeoffW wrote:
>>Hi Stuart
>>Can you clarify what margin thresholds you used and was the distance to the leaf
>>before or after you made a move ?
>>     Geoff
>Sure. Margins were 3 pawns for futility pruning at depth == 1 (before
>the makemove), 5 pawns for extended futility pruning at depth == 2
>(before the makemove), and 9 pawns for limited razoring at depth == 3
>(before the makemove).
>In the first two cases, if found to prune, the node simply isn't searched
>and skipped to the next move. In the last case, if found true, then the
>depth is decremented for that move only by one additional ply.

Do you know if the conditions are ever being properly triggered?

In a depth 11 search on WAC 175 (a position I picked at random), I have these
statistics in a modified Crafty with the pruning described below:

Elapsed Time: 28.77, CPU Time: 27.62, CPU Use: 96%
Root Material Balance: -200, Predicted Moves: 0
Nodes: 12146603, Evaluations: 9251784, FH%: 97%, NPS: 422k
Threat: 174, Check: 679610, One Move: 21736
Passed Pawn: 920, Recapture: 24192
PRUNING->  Futility: 4329693, Razors: 405194

I implemented a variation of the Heinz/DT futility in Crafty (instead of
returning a static score where pruning happens, I had it drop into qsearch for
much more accuracy).  I don't know how the node count compares to a regular
version, or how much the savings for futility is.  I'm sure someone else can run
a default Crafty with futility on and off and report the exact differences.

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