Author: Robert Hyatt
Date: 07:55:46 09/28/01
Go up one level in this thread
On September 28, 2001 at 00:58:15, Dann Corbit wrote: >On September 27, 2001 at 23:44:19, Robert Hyatt wrote: > >>On September 27, 2001 at 19:05:43, Dann Corbit wrote: >> >>>On September 27, 2001 at 17:48:32, Peter Fendrich wrote: >>>[snip] >>>>Yes, I buy all that. My intention was to oppose to the "it's impossible" >>>>statement. You are talking about some general case. There is no reason why each >>>>move has to be 20% because the first one is. That's why I'm talking about >>>>isolating cases where the other move might be better. Another question is what >>>>happens if the ponder move has only 10% or 5% probability. >>>>I have no proofs that these cases are possible to identify but I'm still open >>>>for it, until I know better... >>> >>>Also, it does not have to be either/or. >>> >>>We could ponder the root for 1/2 of the extrapolated opponent time slice, and at >>>that point, change to the pm and ponder that. >>> >>>It seems to me that there are many possibilities. >>> >>>Something that is puzzling me... >>>If one move is really much better than the others, then we would think that it >>>would fail high, re-search, and gobble most of the time anyway. If that does >>>not happen, then some of the alternatives must be pretty good. >>> >>>So, why does pondering root yield only a 2% gain, and pondering the pm give an >>>enormous one? >>> >>>It still does not make sense to me. >>> >>>I guess I'm just having a hard time understanding why it is so much better to >>>ponder the pm instead of the root. >> >>If by "root" you mean the position _before_ any opponent move, then the reason >>is obvious... you will spread your time over N moves, which means that when >>the opponent moves, you will have looked at the _right_ move only 1/N of the >>time. You still have a long time to search to meet the target time for this >>search. > >By the root, I mean "the root move for the opponent -- after I have made my move >but before the opponent returns the response. In other words, the opponent's >current position. > >If the search is so even that time is distributed over N moves, then the chance >of picking the right one is only 1/N anyway. > >If two or three moves are far better than the others, then most of the time will >have been spent searching them. This is not correct. We are using alpha/beta remember. The _best_ move will consume about 75% of the total search time. The next best move will take a tiny fraction of that to prove it is worse, even if it is only .01 worse. > >If one move is dominatingly better, then most of the time will have been spent >searching that time anyway (because of fail-highs). It really doesn't matter whether it is .01 better or 10.0 better. The first (best) move takes the majority of the total search time... > >Now, that's on the one hand. On the other hand, picking the right move to >ponder probably has a big kick of extra value. That's because I often see test >positions that computers cannot solve in a long search, but once they get the >key move, they solve it immediately.
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.