Author: KarinsDad
Date: 07:44:06 08/04/99
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On August 03, 1999 at 19:27:18, Ricardo Gibert wrote: [snip] >> >>If you are in a mate in 110 situation (probably extremely rare), it would >>probably behoove you to do your own searching for capture/push moves that lead >>to positions that maintain the win since you will probably find them relatively >>close to the main line anyway. Compared to searching even something as simple as >>an 8 ply alpha-beta, searching for those moves would take VERY little time. The >>reason this works out so well is that you do not have to search outside the >>tablebase once you are in it (or once you are close enough to it to force your >>way into it). > >In many pawnless EGs a "good" capture can be hard to come by. 8 ply would not do >it in that case. > One other note on this. When you have moves that lead to mate, but they lead to mate 110 moves (i.e. 220 ply, I believe this is what you were trying to discuss) later, you have the option of searching for win preserving moves at ply 1, ply 3, ply 5, etc. Everytime it is your turn, you can attempt to find a win preserving move which has a pawn push or a capture. Granted, you will not be able to search REAL far each time, but even if you only had a second per move, it would take at most two minutes total to search down 6 ply each and every time (i.e. 50 times at ply 1, 3, 5, 7, etc. for a maximum of about 120 moves or 240 ply for your 220 ply best case) before a capture or push was needed. This assumes that you can load up a given 5 piece tablebase into memory (or most of it) and use it (since you will be in a position of not capturing, you will continue to be in the same tablebase). It also assumes that you can search just as far into a tablebase as you could search normally in your search/eval which on the surface, appears to be a slam dunk assumption. Most likely, you could search even faster and farther with the tablebase. Anyway, my basic point is that you would not HAVE to search far. Sooner or later, you would most likely find a win preserving move within 6 or 8 ply (depending on how much time you have and how far you can search the tablebase) since you have 50 of your moves (99 ply) in which to "get lucky". It should happen eventually almost every time (although there may be some extreme cases where it would not). The bottom line is that this approach would win extremely rare games that broke the 50 move rule, but at the same time would not introduce a major change into the tablebases. KarinsDad :)
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