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For Marco---possible Stockfish bug
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Joona Kiiski



Joined: 18 Jan 2009
Posts: 546
PostPost subject: Re: For Marco---possible Stockfish bug    Posted: Wed Feb 01, 2012 8:32 pm Reply to topic Reply with quote
lech wrote:
I changed (in Stockfish 2.1.1)

Code:


 if (!Root && value > alpha)
          {
              if (PvNode && value < beta) // We want always alpha < beta
{
                  alpha = value;



to:


Code:


 if (!Root && value > alpha)
          {
              if (PvNode && value <= beta) // We want always alpha < beta
{
                  alpha = value;



And now Stockfish can solve this position.
My theory has the position, which should be solved by Stockfish.
8th point in search give a right to watch the solution.
My theory says, that in pvnode it would be good to accept alpha = beta.
I changed the code (above) and Stockfish solved this position.
I think it is a very interesting theme for programmers.


The problem is that modern chess engines are very chaotic process. Changing one piece-square table value by one unit could as well make SF to solve the position.

By making to SF to solve one specific position, one can justify almost any change. What we need is a logical reasoning: why do you think that algorithmically it's better to allow alpha := beta. Give one (hypothetic) example situation where this could make positive difference.
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Display posts from previous:   
Subject Author Date/Time
For Marco---possible Stockfish bug Louis Zulli Tue Jan 31, 2012 5:49 pm
      Re: For Marco---possible Stockfish bug Marco Costalba Tue Jan 31, 2012 7:12 pm
      Re: For Marco---possible Stockfish bug Joona Kiiski Wed Feb 01, 2012 7:56 am
            Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 10:02 am
                  Re: For Marco---possible Stockfish bug Joona Kiiski Wed Feb 01, 2012 12:48 pm
                        Re: For Marco---possible Stockfish bug Louis Zulli Wed Feb 01, 2012 2:41 pm
                              Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 7:15 pm
                                    Re: For Marco---possible Stockfish bug Marco Costalba Wed Feb 01, 2012 7:23 pm
                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 9:05 pm
                                    Re: For Marco---possible Stockfish bug Joona Kiiski Wed Feb 01, 2012 8:32 pm
                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 9:02 pm
                                                Re: For Marco---possible Stockfish bug Joona Kiiski Thu Feb 02, 2012 8:30 am
                                                      Re: For Marco---possible Stockfish bug Marek Kwiatkowski Thu Feb 02, 2012 8:36 am
                                                            Re: For Marco---possible Stockfish bug Joona Kiiski Thu Feb 02, 2012 10:52 am
                                                                  Re: For Marco---possible Stockfish bug Marek Kwiatkowski Thu Feb 02, 2012 2:08 pm
                                                                        Re: For Marco---possible Stockfish bug Joona Kiiski Thu Feb 02, 2012 3:45 pm
                                                                              Re: For Marco---possible Stockfish bug Marek Kwiatkowski Thu Feb 02, 2012 5:32 pm
                                                                                    Re: For Marco---possible Stockfish bug david nash Thu Feb 02, 2012 6:14 pm
                                                                                    Re: For Marco---possible Stockfish bug Richard Vida Thu Feb 02, 2012 7:23 pm
                                                                                          Re: For Marco---possible Stockfish bug Marco Costalba Thu Feb 02, 2012 8:04 pm
                                                                                          Re: For Marco---possible Stockfish bug Robert Wagner Campos Thu Feb 02, 2012 8:59 pm
                                                                                          Re: For Marco---possible Stockfish bug Uri Blass Thu Feb 02, 2012 10:41 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Thu Feb 02, 2012 9:01 pm
                                                                                          Re: For Marco---possible Stockfish bug Sven Schüle Thu Feb 02, 2012 11:28 pm
                                                                                          Re: For Marco---possible Stockfish bug Robert Wagner Campos Fri Feb 03, 2012 12:26 pm
                                                                                          Re: For Marco---possible Stockfish bug Uri Blass Fri Feb 03, 2012 2:14 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Fri Feb 03, 2012 2:21 pm
                                                                                          Re: For Marco---possible Stockfish bug Evert Glebbeek Fri Feb 03, 2012 2:41 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Fri Feb 03, 2012 2:58 pm
                                                                                          Re: For Marco---possible Stockfish bug Sam Hamilton Fri Feb 03, 2012 3:23 pm
                                                                                          Re: For Marco---possible Stockfish bug Evert Glebbeek Sat Feb 04, 2012 7:07 am
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Sat Feb 04, 2012 9:31 am
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Sun Feb 05, 2012 4:20 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Sun Feb 05, 2012 5:24 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 08, 2012 1:54 pm
                                                                                          Re: For Marco---possible Stockfish bug Joerg Oster Wed Feb 08, 2012 5:14 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 08, 2012 5:49 pm
                                                                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Sun Feb 19, 2012 5:37 pm
                                                                                          Re: For Marco---possible Stockfish bug Robert Wagner Campos Fri Feb 03, 2012 6:33 pm
                                                                                          Re: For Marco---possible Stockfish bug Robert Wagner Campos Fri Feb 03, 2012 6:15 pm
                                                                                          Re: For Marco---possible Stockfish bug Louis Zulli Sat Feb 04, 2012 1:50 am
                                                Re: For Marco---possible Stockfish bug Marek Kwiatkowski Fri Feb 03, 2012 2:08 pm
                                                      Re: For Marco---possible Stockfish bug Kevin Hearn Fri Feb 03, 2012 3:49 pm
                                                            Re: For Marco---possible Stockfish bug Marek Kwiatkowski Fri Feb 03, 2012 6:45 pm
                              Re: For Marco---possible Stockfish bug Joerg Oster Wed Feb 01, 2012 8:38 pm
                                    Re: For Marco---possible Stockfish bug Louis Zulli Wed Feb 01, 2012 9:14 pm
                                          Re: For Marco---possible Stockfish bug Joerg Oster Thu Feb 02, 2012 7:23 am
                                                Re: For Marco---possible Stockfish bug Marek Kwiatkowski Thu Feb 02, 2012 8:29 am
                                    Re: For Marco---possible Stockfish bug Louis Zulli Wed Feb 01, 2012 9:38 pm
                                          Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 9:54 pm
                                                Re: For Marco---possible Stockfish bug Louis Zulli Wed Feb 01, 2012 11:05 pm
                                                      Re: For Marco---possible Stockfish bug Marek Kwiatkowski Wed Feb 01, 2012 11:11 pm
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