Author: Ed Schröder
Date: 05:32:35 08/03/03
Go up one level in this thread
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
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