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Comparative nodes per second
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Don Dailey



Joined: 29 Apr 2008
Posts: 4323
PostPost subject: Re: Comparative nodes per second    Posted: Thu Apr 19, 2012 10:22 pm Reply to topic Reply with quote
José Carlos wrote:
Don wrote:
lucasart wrote:
Uri Blass wrote:
Here is another example for the huge positional score of chess programs(probably also includes IvanHoe that I did not install in my computer and at least it includes robbolito0.09w32 and houdini that gives more than +4 for white at depth 1 when the program cannot see the promotion by search because it is hidden by a lot of checks)

Toga1.2.1a gives 1.17 for black at depth 1 but toga is inferior old program
and I believe that all the programs that are at the playing strength of Rybka3 or higher give a big advantage for white when they search to depth 1 inspite of nominal 6 pawns advantage by black.

[D]7k/PP5p/2PP3p/7p/7p/7p/6r1/K7 b - - 0 1
   ::    ::    ::    BK
WP WP ::    ::    :: BP
   :: WP WP    ::    BP
::    ::    ::    :: BP
   ::    ::    ::    BP
::    ::    ::    :: BP
   ::    ::    :: BR ::
WK    ::    ::    ::    

???
it's black's turn to play in your fen, and it's very obvious that black has an unstoppable passed pawn on h3. the eval should already return a big score for black without even a search!


These positions only illustrate what is already well known, that humans don't evaluate positions the same way that computers do but instead reason about the position. I would remind you that in this case it usually involves not just evaluation but look-ahead - you are looking ahead here to know that there will be a checkmate in 2 moves. You didn't process this in your brain statically.

Computers use a version of the same process and it's called null move search. We will never (in my opinion) have computers match the human brain and it may not even be desirable to try - computers are much different and trying to force them to do things the same way is like trying to force a human to run on all fours because it works for Cheeta's.

In your example of course we know that a computers static evaluation function is not very good at sorting out what is most relevant. That can be improved incrementally with a more sophisticated evaluation function for specific cases but a general solution is probably going to make programs a lot weaker - simply because it will slow the program down enormously and only be useful once in a while. Even the position you show is not a problem for any chess program doing 1 or 2 more ply - although it's easily understood that you can compose arbitrarily more and more difficult cases.


Hi. I'm experimenting with the concept of "search instability". I don't try to evaluate positions like the above one correctly, but I try to identify positions where the static eval is not reliable. I use it to shape the tree, cutting off soon on "boring" positions and extending the most complicated ones.


You can think of the evaluation score as a win probability score which can be converted via a logistic formula. I have not yet tried to make this idea really work yet, but you can build uncertainty into your evaluation function by "pushing" the score towards zero. For example multiplying the score by a fraction such as 0.80 will bring it closer to zero. So the way you might attempt to apply this is that if you know you have some feature that is volatile, in other words it could easily go your way or against you, then there is great uncertainty in the outcome. Here is an example: Suppose you are a knight up, but BOTH sides have huge (and equal) king safety troubles. A knight up implies that you have nearly a certain win, but I don't think that is the case in the scenario I am describing.

That explanation is simplistic, but the concept is that chess programs deal with uncertainty primarily, we just don't think of it that way. Also, I'm not sure that an evaluation score of 1.5 pawns based on a deep search is the same as an evaluation score of 1.5 based on a leaf node at the end of a quies search. I'm not sure there is anything you can do about that but it seems important to me. Would you rather have a position that a strong program has searched to 30 ply and says is winning by 3 pawns or one that a quies search from the same program says is winning by 3 pawns?

A related issue is making your program fight for a win or draw in a lost position. Let's say you are down 1 pawn. I think that your opponents king safety is more important that it normally would be. If you are down 1 pawn you are probably going to lose assuming the evaluation is more or less accurate, you have serious trouble. I would think that your opponent king safety should be given different weight than your own so that the program is more likely to fight for the win. Conversely, if the program seems to be winning materially, you might want to be a little extra paranoid about your king.

I think these things tend to be linear in most programs, but probably they should not be. In fact this may partially solve the problem where programs put too much weight on things that are not very relevant - such as being up a couple of pawns but the pawns are so horrible that in reality you may not even have an advantage. So the concept could possibly be that certain evaluation features take on more weight (positive and negative) features depending on things that are often not directly correlated with those features.

Quote:


I don't have enough computer time to test the idea and report results, but at least it doesn't look bad at first sight.

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Subject Author Date/Time
Comparative nodes per second Larry Kaufman Tue Apr 10, 2012 7:49 pm
      Re: Comparative nodes per second Vincent Diepeveen Tue Apr 10, 2012 8:16 pm
      Re: Comparative nodes per second Marco Costalba Tue Apr 10, 2012 8:41 pm
            Re: Comparative nodes per second Larry Kaufman Tue Apr 10, 2012 9:02 pm
                  Re: Comparative nodes per second Thomas Petzke Tue Apr 10, 2012 9:30 pm
            Re: Comparative nodes per second Richard Vida Tue Apr 10, 2012 10:15 pm
                  Re: Comparative nodes per second Larry Kaufman Tue Apr 10, 2012 10:18 pm
                        Re: Comparative nodes per second Sam Hamilton Tue Apr 10, 2012 10:54 pm
                        Re: Comparative nodes per second Richard Vida Tue Apr 10, 2012 11:28 pm
                              Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 4:52 am
            Re: Comparative nodes per second Don Dailey Wed Apr 11, 2012 11:23 pm
                  Re: Comparative nodes per second Don Dailey Wed Apr 11, 2012 11:50 pm
                        Re: Comparative nodes per second Sam Hamilton Thu Apr 12, 2012 12:07 am
      Re: Comparative nodes per second Robert Hyatt Tue Apr 10, 2012 9:31 pm
            Re: Comparative nodes per second Larry Kaufman Tue Apr 10, 2012 9:35 pm
                  Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 1:10 am
      Re: Comparative nodes per second Daniel Shawul Tue Apr 10, 2012 11:41 pm
            Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 5:05 am
                  Re: Comparative nodes per second Sam Hamilton Wed Apr 11, 2012 5:28 am
                        Re: Comparative nodes per second Marco Costalba Wed Apr 11, 2012 5:58 am
                              Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 1:04 pm
                  Re: Comparative nodes per second Daniel Shawul Wed Apr 11, 2012 12:27 pm
      Re: Comparative nodes per second Jon Dart Wed Apr 11, 2012 1:59 pm
            Re: Comparative nodes per second Sam Hamilton Wed Apr 11, 2012 2:25 pm
                  Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 2:36 pm
                        Re: Comparative nodes per second Jon Dart Wed Apr 11, 2012 3:06 pm
            Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 2:28 pm
                  Re: Comparative nodes per second Jon Dart Wed Apr 11, 2012 3:10 pm
                        Re: Comparative nodes per second Larry Kaufman Wed Apr 11, 2012 3:59 pm
                              Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 1:19 am
                  Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 1:15 am
                        Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 1:35 am
                              Re: Comparative nodes per second Sam Hamilton Thu Apr 12, 2012 2:32 am
                                    Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 2:50 am
                                          Re: Comparative nodes per second Sam Hamilton Thu Apr 12, 2012 3:10 am
                                                Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 3:35 am
                              Re: Comparative nodes per second Jon Dart Thu Apr 12, 2012 2:37 pm
                                    Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 3:24 pm
                                          Re: Comparative nodes per second Jon Dart Thu Apr 12, 2012 4:25 pm
                                                Re: Comparative nodes per second Don Dailey Thu Apr 12, 2012 4:33 pm
                                                      Re: Comparative nodes per second Jon Dart Thu Apr 12, 2012 4:41 pm
                                                      Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 8:13 pm
                                                            Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 9:00 pm
                                                            Re: Comparative nodes per second Daniel Homan Thu Apr 12, 2012 9:52 pm
                                                                  Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 11:26 pm
                                                                        Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 11:40 pm
                                                                              Re: Comparative nodes per second Sam Hamilton Thu Apr 12, 2012 11:51 pm
                                                                              Re: Comparative nodes per second Robert Hyatt Sat Apr 14, 2012 4:23 am
                                                                        Re: Comparative nodes per second Uri Blass Sat Apr 14, 2012 5:05 pm
                                                                              Re: Comparative nodes per second Robert Hyatt Sat Apr 14, 2012 6:46 pm
                                                                                    Re: Comparative nodes per second Don Dailey Sat Apr 14, 2012 6:56 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Sun Apr 15, 2012 4:31 am
                                                                                    Re: Comparative nodes per second Larry Kaufman Sat Apr 14, 2012 7:47 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Sun Apr 15, 2012 4:36 am
                                                                                          Re: Comparative nodes per second Larry Kaufman Sun Apr 15, 2012 4:47 am
                                                                                          Re: Comparative nodes per second Robert Hyatt Mon Apr 16, 2012 7:14 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Tue Apr 17, 2012 3:02 pm
                                          Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 6:50 pm
                                                Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 8:12 pm
                                                      Re: Comparative nodes per second Robert Hyatt Sat Apr 14, 2012 4:28 am
                                                            Re: Comparative nodes per second Larry Kaufman Sat Apr 14, 2012 4:45 am
                                                                  Re: Comparative nodes per second Robert Hyatt Sat Apr 14, 2012 4:46 pm
                                                                        Re: Comparative nodes per second Larry Kaufman Sat Apr 14, 2012 5:10 pm
                                                                              Re: Comparative nodes per second Sam Hamilton Sat Apr 14, 2012 5:35 pm
                                                                              Re: Comparative nodes per second Robert Hyatt Sun Apr 15, 2012 4:38 am
                                                                                    Re: Comparative nodes per second Larry Kaufman Sun Apr 15, 2012 4:51 am
                                                                                          Re: Comparative nodes per second Robert Hyatt Mon Apr 16, 2012 7:20 pm
                                                                                    Re: Comparative nodes per second Don Dailey Sun Apr 15, 2012 12:14 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Mon Apr 16, 2012 7:21 pm
                                                                  Re: Comparative nodes per second Uri Blass Sat Apr 14, 2012 5:17 pm
                                                                        Re: Comparative nodes per second Larry Kaufman Sat Apr 14, 2012 5:22 pm
                                                                              Re: Comparative nodes per second Uri Blass Sat Apr 14, 2012 5:36 pm
                                                                                    Re: Comparative nodes per second Larry Kaufman Sat Apr 14, 2012 5:47 pm
                                    Re: Comparative nodes per second Sam Hamilton Thu Apr 12, 2012 4:49 pm
                                          Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 5:14 pm
                                                Re: Comparative nodes per second Jon Dart Thu Apr 12, 2012 6:00 pm
                                                      Re: Comparative nodes per second Uri Blass Thu Apr 12, 2012 6:37 pm
                                                            Re: Comparative nodes per second Jon Dart Thu Apr 12, 2012 6:50 pm
                                                            Re: Comparative nodes per second Uri Blass Thu Apr 12, 2012 6:53 pm
                                                                  Re: Comparative nodes per second Lucas Braesch Sun Apr 15, 2012 4:56 am
                                                                        Re: Comparative nodes per second Uri Blass Sun Apr 15, 2012 5:16 am
                                                                              Re: Comparative nodes per second Lucas Braesch Sun Apr 15, 2012 7:58 am
                                                                        Re: Comparative nodes per second Don Dailey Sun Apr 15, 2012 1:10 pm
                                                                              Re: Comparative nodes per second Uri Blass Sun Apr 15, 2012 2:48 pm
                                                                                    Re: Comparative nodes per second Don Dailey Sun Apr 15, 2012 3:26 pm
                                                                                    Re: Comparative nodes per second Robert Hyatt Tue Apr 17, 2012 5:17 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 6:05 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Tue Apr 17, 2012 7:11 pm
                                                                                          Re: Comparative nodes per second Don Dailey Tue Apr 17, 2012 6:06 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 6:16 pm
                                                                                          Re: Comparative nodes per second Don Dailey Tue Apr 17, 2012 6:45 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 6:55 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Tue Apr 17, 2012 7:16 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 7:25 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Tue Apr 17, 2012 7:59 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 8:14 pm
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Tue Apr 17, 2012 10:33 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Tue Apr 17, 2012 10:51 pm
                                                                                          Re: Comparative nodes per second Vincent Diepeveen Wed Apr 18, 2012 12:12 am
                                                                                          Re: Comparative nodes per second Sam Hamilton Wed Apr 18, 2012 12:28 am
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Wed Apr 18, 2012 2:28 am
                                                                                          Re: Comparative nodes per second Sam Hamilton Wed Apr 18, 2012 4:32 am
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Wed Apr 18, 2012 4:44 am
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Tue Apr 17, 2012 10:28 pm
                                                                              Re: Comparative nodes per second José C. Martínez Galán Wed Apr 18, 2012 6:16 am
                                                                                    Re: Comparative nodes per second Robert Hyatt Thu Apr 19, 2012 9:53 pm
                                                                                    Re: Comparative nodes per second Don Dailey Thu Apr 19, 2012 10:22 pm
                                                                                          Re: Comparative nodes per second José C. Martínez Galán Thu Apr 19, 2012 10:49 pm
                                                                                          Re: Comparative nodes per second Robert Hyatt Thu Apr 19, 2012 11:21 pm
                                                                                          Re: Comparative nodes per second Marco Costalba Fri Apr 20, 2012 5:18 am
                                                                                          Re: Comparative nodes per second Michel Van den Bergh Fri Apr 20, 2012 6:10 am
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Fri Apr 20, 2012 11:35 am
                                                                                          Re: Comparative nodes per second Don Dailey Fri Apr 20, 2012 10:57 am
                                                                                          Re: Comparative nodes per second Marco Costalba Fri Apr 20, 2012 1:58 pm
                                                                                          Re: Comparative nodes per second Sam Hamilton Fri Apr 20, 2012 2:19 pm
                                                                                          Re: Comparative nodes per second Miguel A. Ballicora Fri Apr 20, 2012 2:29 pm
                                                                                          Re: Comparative nodes per second Don Dailey Fri Apr 20, 2012 3:13 pm
                                                                                          Re: Comparative nodes per second Don Dailey Fri Apr 20, 2012 4:52 pm
                                                                                          Re: Comparative nodes per second Uri Blass Sat Apr 21, 2012 6:03 am
                                                                                          Re: Comparative nodes per second Marco Costalba Sat Apr 21, 2012 8:14 am
                                                                                          Re: Comparative nodes per second Ed Schroder Sat Apr 21, 2012 10:50 am
                                                                                          Re: Comparative nodes per second Marco Costalba Sat Apr 21, 2012 11:13 am
                                                                                          Re: Comparative nodes per second Don Dailey Fri Apr 20, 2012 12:31 pm
                                                                                          Re: Comparative nodes per second Dan Andersson Fri Apr 20, 2012 4:14 pm
                                                                                          Re: Comparative nodes per second Don Dailey Fri Apr 20, 2012 4:38 pm
                                                            Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 7:10 pm
                                                Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 6:55 pm
                                                      Re: Comparative nodes per second (early results) Robert Hyatt Thu Apr 12, 2012 7:36 pm
                              Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 7:13 pm
                                    Re: Comparative nodes per second Larry Kaufman Thu Apr 12, 2012 8:18 pm
                                          Re: Comparative nodes per second Robert Hyatt Thu Apr 12, 2012 8:55 pm
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