Author: Jeremiah Penery
Date: 12:48:21 04/03/00
Go up one level in this thread
On April 03, 2000 at 15:37:29, Robert Hyatt wrote: >On April 03, 2000 at 15:28:51, Jeremiah Penery wrote: > >>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 > > >No doubt. But how many real positions do you search, vs positions where a >queen sac wins? Best to put your money on the cases you expect to see most >often? The queen sac was an extreme example. The sac of any material will often produce the same problem. In many other cases I've seen the score for a 'non-best' move be only 0.01 above the 'best' move. I'm not quite sure what this means, but it happens frequently. At least frequently enough to be fairly noticable. :) Jeremiah
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