Author: Eugene Nalimov
Date: 16:40:04 09/11/99
Go up one level in this thread
There is one more possible use of mate score: if current alpha/beta is "lost/mate in N plies", and we started to search depth N+1, and it's not mate, you can return immediatelly, without need to do *any* search. Eugene On September 11, 1999 at 09:33:32, Robert Hyatt wrote: >On September 11, 1999 at 06:53:00, Dezhi Zhao wrote: > >>Posted by Robert Hyatt on September 10, 1999 at 00:19:37: >> >>[snip] >> >>>If you recall the discussion here a couple of weeks ago, I reported that I store >>>absolute mate scores (EXACT scores) in the hash table, and that I adjust them >>>so that they are always stored as "mate in N from the current position". This >>>has always worked flawlessly for me, and still does. >> >>>For bounds, I once tried adjusting the bounds as well, but found quirks, and >>>left them alone. Wrong answer. To fix this mate in 4 problem, I decided to >>>adjust the bounds as well, but I now set any bound value that is larger than >>>MATE-300, by reducing it to exactly MATE-300, but still using the "LOWER" >>>flag to say that this is the lowest value this position could have. For bound >>>values < -MATE+300, I set them to exactly -MATE+300 and leave the flag as is. >> >>Hi! >> >>If I understand correctly, you relax the bound mate scores to safe values, so >>that these bounds will not produce cutoffs when compared with other mate scores >>(esp. of EXACT type), but the bound will still generate cutoffs when compared >>with non-mate scores. >> >>I used to adjust the bound mate scores and the exact mate scores in the same >>way, and have not found any problems so far. >> >>Therefore, my question is: >>Why the adjusted bounds should not be compared with other mate scores and thus >>produce cutoffs? >> >>It seemed to me that the relaxed bounds would produce less cutoffs than the >>adjusted ones which are tighter. However, when I tried out your relaxed bounds >>on some mate positions, I found that your relaxed bounds save a lot (~ 12%)! >>Thanks to Dr. Hyatt! > >I'm not sure why it saves a lot, but I do understand why it is better. The >position from Steffen found a score (Mate in 4 but it wasn't forced) and this >became a bound. Later it found a mate in 5, but since this was worse, it >stored >= Mate-in-4 for that position. Later it found that same position 4 >plies deeper and said >=Mate-in-4 which is now wrong... It is really >= >Mate-in-6 since we are 4 plies deeper than before. > >This made crafty find a mate in 4 in the actual game, when was really a mate in >6. > >I tried it with the 'relaxed bounds' and it had no problems I could find with >over 500 mate-in-N test positions... > >It was harder to find than to fix, naturally. :) > > >> >>Any explainations? Can we find a even better way of using mate bounds? > >None. I am going to experiment with adjusting the bounds (Mate) as well. >However, I did this when I first added hashing to Crafty and ran into something >that was a real pain. It is probably given in the comments in main.c, but I >want to go back and understand why what I did was not working. Might be that >there were other bugs at the time... > > > >> >>Dezhi Zhao
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.