Author: Uri Blass
Date: 23:29:32 09/27/01
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. I think that here is your mistake. The fact that the predicted move is calculated only for 1/10 of the time does not mean that the probability that you ponder correctly is 1/10. I guess that the probability that you ponder correctly is smaller when the predicted move is calculated for less time but the ratio is not linear. I did not investigate the probability to ponder correctly as a function of the ratio between the time that was used to calculate the best move adn the time that was used to calculate the first 2 moves of the main line. Example to explain what I mean Suppose that the program calculated the opening position for 180 seconds. Suppose that the main line is 1.e4 c5 suppose that 1.e4 was calculated for 100 seconds Suppose 1.e4 c5 was calculated for 10 seconds in this case you assume that the probability that you ponder correctly is 10/100=1/10 I think that this assumption is wrong. I believe that the probability is smaller when the calculated number(in this case 10/100) is smaller but it is not the number that you calcualted and I think that it is not small enough to justify not pondering the predicted move. It is possible that if you combine the condition that the calculated number is small with other conditions you may find cases when it is not a good idea to calculate the predicted move and it is better to calculate the position before the opponet's move in part of the time. Uri
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