Author: Sune Fischer
Date: 08:34:28 09/18/04
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On September 18, 2004 at 07:02:22, Andrew Platt wrote: >On September 18, 2004 at 04:05:38, Sune Fischer wrote: > >> >>I decided to try out the triangular PV thing Bob >>speaks so highly of, to see if it improves move ordering... >> >>I was careful to terminate the PV on all exact scores - of course. >>Still I was getting illegal moves in the PV. >> >>It turned out to be a hash/nullmove problem. > >There's no score that could be responsible for having illegal moves in the PV. >There are two main things I had to take care of to get rid of illegal moves: > >a) Make sure you truncate the PV for the ply you are entering before you start >doing a null move / iterating through the move list / internal iterative >deepening, etc.. In other words before you do anything that will increase the >current ply. Obviously since you are using a triangular array, you aren't >touching the PV stored higher up when you do this. This might work, but I think you have to update the PV instantly on all new PV nodes, otherwise you will overwrite the child PV at the next move. Currently I wait with the PV copying to the end of that node when all the moves have been searched, then I only have to update the PV once (or maybe not at all if there is a FH move before that). >b) If you update the PV in qsearch and you can generate illegal moves there, you >will have to take special action. I just don't update the PV in qsearch which is >the easy way out! No PV in qsearch. I doubt it is worth it, it would have to be a test for another day. :) -S. >Andy.
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