Author: Dan Homan
Date: 11:24:54 08/20/99
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On August 20, 1999 at 13:40:28, James Robertson wrote: >On August 20, 1999 at 12:24:44, Jon Dart wrote: > >>Actually, the first thing I'd look for is the logic you have for >>storing and retrieving hash values. If you do not always correctly >>identify the node type (fail-high, fail-low, or in bounds) or >>if you do not properly set the search bounds after a hash hit, >>you will have problems like you describe. Having "almost right" >>logic will appear to work for a while, but sooner or later you >>will pull a bad value out of the hash table and you will be >>hosed. >> >>Unlike many areas of computer chess, there is really only one >>right way to do this. Look at Arasan, Crafty, or Gnuchess source >>and do what they do (in Crafty, look at hash.c). >> >>--Jon > >I have tried to look at Arasan source several times and was always completely >confused. Crafty is confusing because the hash stuff is split between 2 files. >EXchess is of some help. The only program that is not confusing is JRCP, and it >has too many bugs. :( The currently released version of EXchess (2.51) has some small bugs in hash handling. I forget exactly what they are... it is basically right, but even small bugs can be a big problem in the right position. One bug that I can remember gives the same behavior as your program... i.e. the MATE score is not always properly adjusted to the ply depth. I can't remember the exact cause, but I think it had something to do with trying to return a MATE score when I only had a bound rather than an exact score in the table. The newer version (currently in progress) has some fixes/improvements in this area and many others. - Dan > >James
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