Author: Roberto Waldteufel
Date: 11:02:13 06/02/98
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On June 02, 1998 at 08:09:12, Robert Hyatt wrote: >On June 02, 1998 at 03:21:38, Stuart Cracraft wrote: > >>So what I hear is that having position-based "learning" >>is something like saving the position after a really bad >>drop in the iteration of a score in the hash table with >>a special flag. When the game ends, write out all >>such entries to a disk based file. When restarting >>the program, read in the disk based file into the >>hash table and set the flags. When searching, if >>the position turns out to be one of those positions, >>then what? >> >>I could dig out my Slate (one or the other forgot which) >>article in ICCA on the "Mouse" program -- is that essentially >>what this Position-Based "Learning" is that some >>programmers are using to create artificial wins against >>other programs? If so, any big refinements to Slate's method >>for the current crop? If no, what are the major differences >>between Slate's method and the current vogue? >> >>Thanks, >>--Stuart > > >all you have to do is write the hash entry out when the score drops, and >reload it before each move from then on, or (as I do) load them once and >flag them as "permanent". That is all you do. Hashing will take care >of >the rest, and you will see the "trouble" several plies earlier the next >time you play the same game, and you will play a different move to avoid >reaching the position where the score is going to drop. Can you clarify this for me - do you keep a permenant file of "bad" positions that you add to with each game played? if so, is there not a risk that eventually the file of permenant positions may become so large as to clog up the hash table with positions that may be irrelavent to the current game? Or is the nimber of stored permenant positions too small to present any problem of this kind. Also, if you make a modification or improvement to the program, then do you have to start from scratch with the permenant positions, or do you just assume that the improved version of the program will misjudge the same positions that it misjudged before, and so leave the permenant position file unchanged? I currently use the idea of "infinite depth" in the hash table: with each entry in the table, the depth has to be stored. If my search finds a forced mate from a position in the search tree, then this evaluation is no longer depth-dependant, so I record the position as having the maximum possible depth, so that it will not get replaced during that game, but when the game is over I discard the hash table instead of saving the permenant positions (in my case, good rather than bad positions). Perhaps I should not discard these positions at the end of the game? Roberto
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