Search found 3285 matches

by lkaufman
Tue Jan 19, 2010 3:12 am
Forum: Computer Chess Club: Tournaments and Matches
Topic: First experience with Igorrit
Replies: 28
Views: 4508

Re: First experience with Igorrit

Based on a huge sample (150k+) of positions from top-level correspondence play, I compared Rybka 3 on one core to Robbolito. At one second per position, Robbolito matched the move choices better than R3 by nearly one percentage point, roughly 50 Elo, in line with your results. However at one minute ...
by lkaufman
Tue Jan 19, 2010 12:45 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Question for Bob Hyatt
Replies: 179
Views: 33396

Re: Question for Bob Hyatt

"i consider rybka's search a piece of crap. Just mainline checking and never trying to find a better move." I'm not saying you are right or wrong, but Vas would never have used this type of search in Rybka if it did not win against a similar evaluation using a conventional search. Do you have any da...
by lkaufman
Mon Jan 18, 2010 3:45 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Rook+pawns vs two minors
Replies: 24
Views: 2835

Re: Rook+pawns vs two minors

It's true that the second extra pawn is more likely to be passed than the first, but Doch considers candidate passed pawns to be almost as important as passed pawns, so I don't think this factor significantly skews the numbers, at least for us. I did a test on a standard theoretical position from th...
by lkaufman
Mon Jan 18, 2010 2:58 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Rook+pawns vs two minors
Replies: 24
Views: 2835

Re: Rook+pawns vs two minors

No, I just mean that we make some effort to choose values in the piece location tables and for "average" mobility that will average out to zero over all positions searched. So for example maybe the "average" extra pawn is on the fourth rank and is a candidate for being passed, so we would use values...
by lkaufman
Mon Jan 18, 2010 2:14 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Rook+pawns vs two minors
Replies: 24
Views: 2835

Re: Rook+pawns vs two minors

Thanks for the examples. In the Doch versions out now, the pieces are reasonably "centered", but the pawn is not, so that even though in Doch 1.2 the Exchange was nominally worth two pawns, in reality it was more like 1.75 pawns, which (together with the factors you mention) explains the scores. In ...
by lkaufman
Mon Jan 18, 2010 1:35 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Rook+pawns vs two minors
Replies: 24
Views: 2835

Re: Rook+pawns vs two minors

In both Rybka and Doch we made some effort to bias the piece-location tables to offset mobility and such factors in all game phases, so that the nominal piece values will be reasonably realistic. For programs I'm not so familiar with, I would just go by the evaluation of some neutral position you mi...
by lkaufman
Mon Jan 18, 2010 12:35 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Rook+pawns vs two minors
Replies: 24
Views: 2835

Re: Rook+pawns vs two minors

"most top engines use rook 2.5 pawns better than a piece. A few use 2.2 pawns, only amateur engines use less than 2.2". Rybka 3 uses almost exactly 2 pawns on average, though the value is heavily phase-dependent. Doch (latest private version) uses 1.97 on average. For Stockfish it's hard to say, bec...
by lkaufman
Sun Jan 17, 2010 5:01 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Question for Bob Hyatt
Replies: 179
Views: 33396

Re: Question for Bob Hyatt

Surely you must be quoting the approximate raw piece values before adding in your "bad trade" numbers, as you are saying that a piece is worth less than three pawns and that two minors are worth way less than rook and pawn, both of which are way outside of anyone else's values. So how large is your ...
by lkaufman
Sun Jan 17, 2010 1:59 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Question for Bob Hyatt
Replies: 179
Views: 33396

Re: Question for Bob Hyatt

Now that you have explained your "bad trade" code a bit, I would say that the most interesting test you could run would be to vary only the "bad trade" parameter to see if its optimum value is different at different levels/time controls. I suspect that the value of each extra piece (your parameter) ...
by lkaufman
Sun Jan 17, 2010 1:52 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Question for Bob Hyatt
Replies: 179
Views: 33396

Re: Question for Bob Hyatt

I'm afraid I have no idea what you are talking about regarding getting information about Rybka values. But I can tell you that when I joined the Rybka team (around the time of version 2.1) the evaluation, both for material and positional terms, was quite bizarre, having been tuned in a purely automa...