Author: Roberto Waldteufel
Date: 14:27:33 04/08/99
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On April 08, 1999 at 16:37:52, Christophe Theron wrote: >On April 08, 1999 at 13:44:11, Roberto Waldteufel wrote: > >>By a threat for the other side, I mean that, if it were in fact the other side's >>turn to play, he would have a capture. Therefore threats by side to move would >>mean that the side to move has one or more legal captures available, which is >>precisely the condition I started out with to trigger an extension. The >>enhancement was to extend if *either side* has pending captures. > >OK, I thought at first it was asymetric. > > >>The whole >>qseearch is easier than in chess precisely because of the obligation to capture >>whenever possible - it is not really a qsearch in the sense we use that term for >>chess > >It is the same than in chess from my point of view. QSearch is: "don't stop >while something is happening". The difference is how you judge that something is >happening... Even in chess you can think of different ways to implement a >QSearch, isn't it? > Yes, exactly so. It is only how I define "something is happening" that is a little bit different because of the different rules of checkers (as compared to chess) when captures are possible. I think if I tried to implement the exact same method in chess, my Qsearch would explode and the search would never terminate. > >>- rather it is an extension of the full width search. The only cases that >>escape this technique are so called "pitch" moves, where neither side has a >>capture, but the side to move deliberately offers a sacrifice of a piece (which >>must be accepted because of the obligation to capture whenever possible) in such >>a position that the material scrificed can either be regained with interest or >>an overwhelming positional superiority can be established by means of the >>sacrifice. >> >>If you ever turn your hand to another game, I can highly recommend checkers. It >>has far more depth and subtlety than I ever thought possible with such a limited >>set of moves compared to chess. The late Dr Marion Tinsley, thought by many to >>be the best (human) player of all time, was also quite a strong chess player in >>his youth. He compared the two games nicely thus: "Chess is like looking out >>over a limitless ocean, whereas checkers is like looking down a bottomless >>well". > >I understand... > > > Christophe > > >>I understand from that quote that in checkers, because of the lower >>branching factor, you can look further ahead, but still sooner or later you must >>reach a horizon where a (possibly erroneous) positional evaluation must be made, >>just as happens in chess and other games. In my experience it is often more >>difficult to describe accurately what constitutes a positional advantage in >>checkers than it is in chess, although that might be because I am not very >>experienced at checkers, whereas I have played, studied and programmed >>competitive chess for many years. >> >>Best wishes, >>Roberto
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