Author: Andrew Platt
Date: 04:02:22 09/18/04
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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. 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! Andy.
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