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KQKP and KRKP endgames
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Miguel A. Ballicora



Joined: 09 Mar 2006
Posts: 4427
Location: Chicago, Illinois, USA
PostPost subject: Re: KQKP and KRKP endgames    Posted: Sat Jun 23, 2012 2:45 pm Reply to topic Reply with quote
syzygy wrote:
Sven Schüle wrote:
That makes a useful predictor slightly more complex (but still doable) ...

I don't really see why a predictor that misses some subtleties would not be useful.

Without any specific rules, the eval will use material balance as predictor. That will incorrectly evaluate many draws as wins for K+Q. With specific rules, most of these draws can be caught at the price of evaluating a few wins for K+Q as draw. Overall that should be an improvement. Inaccuracies in the evaluation are inevitable, which is the reason to do a search.

Of course a not completely accurate predictor should not be used to abort the search at an internal tree node.


Exactly. Inaccurate predictors should not be used in search, but could be used in eval. However, these type of positions are very deceiving. We had a thread about it ~1.5 year ago with Robert Houdart and Richard Vida about it. A very simplistic approach may even be worse than nothing if done carelessly. I have seen it when I was working on this. Search is really tricky to find wrong exceptions, stick them in hash, and the whole thing gets difficult.

If a simplistic case is applied, it should be better to include only basic cases in which you are 100% sure the position is predicted well (draws in this case), and let the other cases be found in search.

I worked hard on this finding all exceptions (validating it with TBs) and coding rules for it. It is not easy. I did not finish the job but I covered most of it in Gaviota. But, the position posted by Sven, Gaviota get it wrong in eval. It finds the draw after one ply though.

Miguel
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Subject Author Date/Time
KQKP and KRKP endgames Lucas Braesch Fri Jun 22, 2012 2:30 pm
      Re: KQKP and KRKP endgames Mincho Georgiev Fri Jun 22, 2012 4:10 pm
      Re: KQKP and KRKP endgames Sven Schüle Fri Jun 22, 2012 4:11 pm
            Re: KQKP and KRKP endgames Lucas Braesch Sat Jun 23, 2012 7:12 am
                  Re: KQKP and KRKP endgames Kevin Hearn Sat Jun 23, 2012 8:45 am
                  Re: KQKP and KRKP endgames Sven Schüle Sat Jun 23, 2012 12:08 pm
                        Re: KQKP and KRKP endgames Sven Schüle Sat Jun 23, 2012 12:24 pm
                              Re: KQKP and KRKP endgames Lucas Braesch Sat Jun 23, 2012 12:36 pm
                                    Re: KQKP and KRKP endgames Sven Schüle Sat Jun 23, 2012 3:19 pm
                              Re: KQKP and KRKP endgames Ronald de Man Sat Jun 23, 2012 1:49 pm
                                    Re: KQKP and KRKP endgames Miguel A. Ballicora Sat Jun 23, 2012 2:45 pm
                                          Re: KQKP and KRKP endgames Ronald de Man Sat Jun 23, 2012 4:05 pm
                                                Re: KQKP and KRKP endgames Sven Schüle Sat Jun 23, 2012 4:19 pm
                                                      Re: KQKP and KRKP endgames Ronald de Man Sat Jun 23, 2012 5:11 pm
                                                            Re: KQKP and KRKP endgames Miguel A. Ballicora Sat Jun 23, 2012 5:37 pm
                                                                  Re: KQKP and KRKP endgames Michel Van den Bergh Sat Jun 23, 2012 6:09 pm
                                                                        Re: KQKP and KRKP endgames Joona Kiiski Sat Jun 23, 2012 6:16 pm
                                                                              Re: KQKP and KRKP endgames Daniel Shawul Sat Jun 23, 2012 6:27 pm
                                                                                    Re: KQKP and KRKP endgames Tord Romstad Sun Jun 24, 2012 6:32 pm
                                                                                          Re: KQKP and KRKP endgames Daniel Shawul Sun Jun 24, 2012 11:17 pm
                                                                                          Re: KQKP and KRKP endgames Robert Hyatt Mon Jun 25, 2012 12:21 am
                                                                  Re: KQKP and KRKP endgames Ronald de Man Sat Jun 23, 2012 6:21 pm
                                                                        Re: KQKP and KRKP endgames Miguel A. Ballicora Sun Jun 24, 2012 7:19 pm
                                                                              Re: KQKP and KRKP endgames Robert Hyatt Mon Jun 25, 2012 12:32 am
                                                                  Re: KQKP and KRKP endgames Robert Hyatt Mon Jun 25, 2012 12:17 am
                                          Re: KQKP and KRKP endgames Thomas Petzke Sat Jun 23, 2012 4:21 pm
      Re: KQKP and KRKP endgames Joona Kiiski Sat Jun 23, 2012 4:44 pm
            Re: KQKP and KRKP endgames Lucas Braesch Sun Jun 24, 2012 3:14 am
            Re: KQKP and KRKP endgames Sven Schüle Sun Jun 24, 2012 10:14 am
                  Re: KQKP and KRKP endgames Ronald de Man Sun Jun 24, 2012 11:05 am
                        Re: KQKP and KRKP endgames Sven Schüle Sun Jun 24, 2012 11:51 am
                              Re: KQKP and KRKP endgames Ronald de Man Sun Jun 24, 2012 12:39 pm
                                    Re: KQKP and KRKP endgames Sven Schüle Sun Jun 24, 2012 2:15 pm
                                          Re: KQKP and KRKP endgames Ronald de Man Sun Jun 24, 2012 2:24 pm
                  Re: KQKP and KRKP endgames Uri Blass Sun Jun 24, 2012 1:24 pm
                        Re: KQKP and KRKP endgames Sven Schüle Sun Jun 24, 2012 1:46 pm
            Re: KQKP and KRKP endgames Uri Blass Sun Jun 24, 2012 1:30 pm
                  Re: KQKP and KRKP endgames Thomas Petzke Mon Jun 25, 2012 7:27 am
            Re: KQKP and KRKP endgames Joona Kiiski Sun Jun 24, 2012 5:13 pm
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