Author: Uri Blass
Date: 10:51:17 08/03/03
Go up one level in this thread
On August 03, 2003 at 13:23:53, Ed Schröder wrote: >On August 03, 2003 at 12:12:07, Uri Blass wrote: > >>On August 03, 2003 at 11:40:52, Ed Schröder wrote: >> >>>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. >>> >>>The first example is about 4 plies at least, if you are going to be simplistic >>>about that as the tenor of your answer certainly is then count me out of this >>>discussion. Mind you, if you have such a case one time in each game overlooking >>>that kind of things your program is dead meat for every decent chess engine. >>> >>> >>>>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 think that cases of 2 plies are already bad enough, I think you are >>>underestimating what the algotithm is all about. On one hand you put a lot of >>>efforts to write a superb evaluation while on the other hand you are killing the >>>same chess knowledge using Lazy Eval. > >>killing seems to me too big word because you use the knowledge if it is relevant >>before the positions of the qsearch. > >Lazy Eval (LE) is reasonable safe when the evaluation is in synch with the >material value. However if the evaluation is pregnant from huge positional >scores such as +2.50 (or so) for king safety or +4.00 for 2 connected passed >pawns on the 6th rank LE is a candidate to kill this chess knowledge, right? the question is what happens when the program detects the positional +2.50 or +4.00 before the qsearch. If at least in these cases your qsearch also detect the +2.50 or +4.00 then the demage is limited and the +2.50 is still prodctive in a lot of cases. Uri
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