Author: José Carlos
Date: 03:49:04 12/15/03
Go up one level in this thread
>>>I have seen worse. What happens is that the aspiration window initially cuts >>>off all mate scores. But once it fails low, it can't just find any old mate >>>and cut off analyzing that line. Now it has to follow _all_ mates and that >>>kills performance. This also happens in endgames where you can potentially >>>promote a pawn, but it always gets lost, so you can search to great depth. >>>And eventually you find that you can promote it there, but now all those lines >>>you got cutoffs on before (where the pawn promoted, but it wasn't forced) now >>>explode and while the depth 25 search took 10 seconds, the depth 26 search might >>>not take 10 days... >>> >>>It's a known problem with no known solution. >>> >>>Even not using aspiration search won't solve it. >> >>You can not lower the window to -INF, but rather on the initial fail low move it >>down -1, then next do -3, and so on. Or just do it for fail-high and that >>should affect fail-low also (since a fail-low on one side is a fail-high for the >>other). > > >Yes you can. We documented that in "using time wisely" and "using time wisely, >revisited" which were published in the JICCA. But it only solves it for >some cases, not the pawn promotion case. Because you _must_ drop it low enough >to let the promotion stand, and that is low enough to let _all_ promotions >stand, which blows the search right out of reality. Some time ago I read an idea I completely forgot to try later. It was about starting the search again from iteration 1 when a fail low occurs at high depth, so that new ordering information (plus actual hash info) could hopefully help in finding a better move faster. Does this idea actually work? (yes, I know, I should try it myself, but I can't until next weekend). José C.
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