Author: Uri Blass
Date: 13:37:26 08/04/03
Go up one level in this thread
On August 04, 2003 at 15:45:26, Matthew White 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. >What if the discovery happens at ply 15? The difference between plies 15 and 17 >in a middlegame could be hours... These were extreme cases and in most of the cases it is not 2 plies. There are cases when it is 0 plies and the difference between 16 plies with knowledge and 16 plies without knowledge can also be hours. Uri
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