Author: William Penn
Date: 19:43:42 12/21/05
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On December 21, 2005 at 21:25:41, Uri Blass wrote: >On December 21, 2005 at 21:18:13, Tansel Turgut wrote: > >>The engine matches between programs seem to be done under fast time controls. >>Does anyone know how good Rybka is in tournament mode (or in infinite mode) >>compared to other programs? > >I do not know but it can change it's mind after a long time and I already saw it >changing it's mind after 2 hours of analysis to a better move. >I guess that it is better than other engines at all time controls. > See http://www.talkchess.com/forums/1/message.html?471773 I have also run a lot of infinite analyses with Rybka. The main thing I notice is a reduction of the analysis outputs to 2 ply at longer time controls. This is position-dependent to some extent, but it appears that eventually the analysis will always truncate to 2 ply with any position. This can happen after only 20 minutes, or may not have happened yet after 1000 minutes, but eventually it will happen. The trend seems clear. So if you are looking for detailed analysis at long run times (many hours), Rybka is not giving it in the current version. The tests in the link above show the same trend. The Rybka author has promised to look at this. A separate question is how good the chosen move is at long run times, and whether it actually improves if you let it run for a longer time. So is the move selected better after 5 hours than after 5 minutes of run time? I don't have any data on this question, although it's important to me. I'm not sure how to devise a test(s) to answer this question. Because long run times take a long time, it is difficult to evaluate them, because it takes such a long time to obtain any such test data (a circular argument, to be sure). It might even be close to impossible!? So maybe it's necessary to use human judgement here, and as regards Rybka, at this point I simply don't know. Re the variability in the analysis as it proceeds from shorter to long run times, Rybka seem fairly inflexible. It does not behave like Shredder, Fruit, Fruit, or other engines I have tried. Rybka may decide very early (in 2-3 minutes) that the best sequence is a certain 12-14 ply of moves, and stick with that exact same sequence of moves for many hours of analysis! This is an exaggeration to make a point. Of course it changes the analysis when it finds a better move or line, but this happens less frequently than with the other engines. Rybka tends to make up its mind early, and then not change it. At least that is my strong impression. WP
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