Author: Dann Corbit
Date: 17:18:18 06/28/99
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On June 28, 1999 at 20:12:20, Dann Corbit wrote: >On June 28, 1999 at 19:38:49, Heiner Marxen wrote: >[snip] >>>Imagin, I am at some node. Now it has been analyzed to 16 plies and the >>>children (of which there are 40 possible) have only 14 entries. Of these two >>>are at 15 plies and 5 at 12 plies and 7 at 9 plies. How can I update the >parent from this? >> >>IMO, not at all. The 16-ply result is already build from 15-ply sub-results. >>Even those cannot improve the 16-ply result. >>You can look at this in a similar way as when you find a hash hit: smaller >>depth than wanted is just not usable. (Exception: mate scores) >I will have to explore this some. I have seen many examples where a parent at >depth 16 does not see what the child sees at depth 15. Perhaps this is due to >null move pruning. It may not be as ludicrous as it sounds because we are >talking about billions of positions examined by this point. If some tiny >fraction of the null moves pruned are wrong, they can point to a wrong result. >Can anyone else think of an explanation as to why a 1 ply inferior child record >should improve the parent result (perhaps a bug?) I do know that I have seen >this happen time and time again. >[snip] Another thing along these lines that probably many of the posters here have seen is when you are trying to solve a tough EPD position in a test suite. You might let the computer run all night and it never finds the move. But if you give the computer the position right after the correct choice, it finds the answer in short order (much less than even exponential drop-off would explain).
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