Author: Matthew White
Date: 12:45:26 08/04/03
Go up one level in this thread
On August 03, 2003 at 08:48:16, Uri Blass wrote: >On August 03, 2003 at 08:32:35, Ed Schröder wrote: > >>On August 03, 2003 at 07:12:30, Uri Blass wrote: >> >>>On August 03, 2003 at 06:54:47, Jonas Bylund wrote: >>> >>>>On August 03, 2003 at 06:50:25, Uri Blass wrote: >>>> >>>>>On August 03, 2003 at 05:45:42, emerson tan wrote: >>>>> >>>>> >>>>>> Of course given enough depth, most chess >>>>>>programs can give good evaluation, but there are still a lot of positions that >>>>>>are far beyond the search depth of top engines on the most powerful hardware, >>>>>>and it is here where chess knowledge is needed. >>>>> >>>>>Based on my understanding increasing the chess knowledge in Rebel is not going >>>>>to help it to understand these positions. >>>>> >>>>>I understood that >>>>>Rebel does the full evaluation at every node except the leaves so I guess that >>>>>if it can see something important in the tree before the leaves then it is going >>>>>to see it also in the leaves. >>>>> >>>>>Cases when something important is generated only in the leaves can be detected >>>>>with less chess knowledge (maybe even faster) thanks to deeper search. >>>>> >>>>>In order to change my mind >>>>>I need to see a case when knowledge does not help to detect the problem one or 2 >>>>>plies earlier but help to detect the problem 10 plies earlier. >>>>> >>>>>If Rebel with full knowledge say +1 for white at plies 5-10 when default Rebel >>>>>say evaluations near +1 for black at plies 5-15 then it is going to be a >>>>>convincing evidence that knowledge in Rebel is what you think about when you use >>>>>that word. >>>>> >>>>>Uri >>>> >>>>But how can we know without trying it? >>>> >>>>This has the potential to be a very interesting experiment! >>>> >>>>Jonas >>> >>>I know that people tried personalities with Rebel century and found that >>>reducing the knowledge of Rebel lead to better results. >>> >>>There was no difference that was observed between blitz and longer time >>>control(Ed did not say based on tests to use knowledge=25 in blitz and >>>knowledge=50 at long time control). >>> >>>I see no reason to believe that things changed. >>>I do not claim that knowledge is not important but that I believe that the name >>>knowledge in Rebel is simply misleading because Rebel does the full evaluation >>>in every node when the remaining depth is positive based on Ed's page. >>> >>>I believe that the lazy evaluation at the leaves miss nothing big that was >>>detected in the previous plies so there is no case that Rebel with knowledge can >>>do clearly better than Rebel without knowledge(in the best case for the full >>>knowledge evaluation it can only find that it is in trouble faster but there are >>>more cases when it can find that it is in trouble faster when the default >>>personality is used) >>> >>>I guess that it may also miss a small positional difference that it does not >>>consider in the lazy evaluation but the important thing in the evaluation is not >>>to miss a big thing and deeper search by 1 ply often more than compensate for a >>>small positional difference. >>> >>>I am not Ed and I may be wrong but if you want to prove that I am wrong then it >>>is better that you start by provifing a position when default Rebel show clear >>>advantage for white at depthes 5-15 when Rebel with maximal knowledge shoe >>>something completely different at depth 5-10. >>> >>>Uri >> >> >>Hi Uri, >> >>While it is true the [Chess Knowledge] parameter is about tuning Lazy Eval you >>shouldn't underestimate the sometimes disastrous effects done to the evaluation >>especially in Q-search. Search and Lazy Eval bite each other, it is a matter of >>feeling and taste to find the best combination represented by the value of the >>[Chess Knowledge] parameter. >> >>Here are some disastrous examples, I am cherry-picking of cousre as these are >>the big exceptions but it shows you how sensitive and sometimes fragile (thus >>important) the whole concept is. >> >>I picked the Rebel-XP engine as I have the examples straight available. >> >>[d]1q2N3/3p1Q2/3p3K/p7/b5k1/8/7P/8 w - - bm Qf2; >> >>[Chess Knowledge = 100] -> not found after 5 minutes and 12 plies. >>[Chess Knowledge = 500] -> 8 seconds, depth=9 >> >>00:00:08.4 1,81 9 7018724 Qf2 >>00:00:08.9 2,38 9 7427943 Qf2 Qb3 >>00:00:10.7 4,17 10 9016929 Qf2 Qb3 >> >>Second example... >> >>[d]2q4r/2p4p/kpnp2p1/p2b4/P6Q/1PR2NP1/2P3BP/2K5 w - - bm Rxc6; >> >>[Chess Knowledge = 100] -> found at depth 10 >>[Chess Knowledge = 500] -> found at depth 8 >> >>Last example.... >> >>[d]r3b1nr/ppqn1k1p/4p1p1/1P1pPpP1/1B1N1P1P/R7/3Q4/R3KB2 w Q - bm Rc3; >> >>[Chess Knowledge = 100] -> 1:53 and 13 plies. >>[Chess Knowledge = 500] -> 0:52 and 11 plies. >> >>Ed > >I see that even in 2 of 3 of the big exceptions the difference is only 2 plies >so my point is that in the best case it can help to detect things faster and >there is no case that Rebel has a completely different evaluation with >knowledge. >This is the reason that I do not believe that it is productive for long time >control. What if the discovery happens at ply 15? The difference between plies 15 and 17 in a middlegame could be hours... Matt > >I could imagine that knowledge may be about detecting a fortress position(or >detecting some dangerous passed pawn that is going to promote only 20 plies >later) so rebel with knowledge is going to see it even after 5 ply search when >default Rebel could not see it even after 15 plies but this is not what >knowledge is about in Rebel. > >I do not claim that knowledge is not important for long time control but that >the knowledge that is needed is not the difference between lazy and not lazy >evaluation in Rebel. > >Uri
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