Author: Jeremiah Penery
Date: 12:28:51 04/03/00
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On April 03, 2000 at 08:57:27, Robert Hyatt wrote: >On April 02, 2000 at 22:39:06, Tina Long wrote: > >>I am suggesting that "If the "score" of the best 3 moves is not too dissimilar" >>increasing the analysis time from about 40min to 4 hours for 2nd & 3rd best May >>find one of them to be actually Best. This is the Benefit to weigh against the >>Cost of the 1st best move being analysed to 19 ply rather than 20 ply. > > >This is the same thing as adding 2+2, but then going over and over the result, >checking yourself, for the next hour. Is your answer any more accurate? Or >did you just spend a lot of time? > >If the second move was searched deeper, that would be different. But _all_ >moves are searched to the same base depth. One thing (probably of many) that can mess this up a bit is null-move pruning. Take WAC #141 for example (the Queen sac for mate) - Pretend that Qxf4 is the second move on your list, and so would show up that way in k-best mode. If you do a normal search, it might take 10 plies to see that Qxf4 is best. However, if you do K-best, you'd see at ply 8 that Qxf4 actually has a higher score. I've seen similar things happen tons of times with Crafty. It finds move X after a normal search to some depth, but when you force it to search some other move, it can find a higher score at the same depth - Why didn't it find the 'better' move the first time? But K-best will find it, most likely. I'm not arguing for K-best to be used in any serious game(s), or that it is any better than normal search. I'm just pointing out that in some cases, it can actually produce something better, due to the imperfections in pruning methods and such. Jeremiah
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