Author: Bert van den Bosch
Date: 05:54:46 08/26/04
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On August 26, 2004 at 03:01:32, Tony Werten wrote: >On August 25, 2004 at 17:37:59, Bert van den Bosch wrote: > >>First of all, I hope the forum will continue in some way! >> >>Before it is gone, I have a question. >> >>I wanted to check my null move so I tested if the null move would create a >>cutoff, and after that I did the normal stuff. So if you have a cutoff with null >>moving you are almost sure you will also get a cutoff with the normal proces, >>except for zugzwangs of course. But this wasn't happening all the time when I >>tested it, and usually the values involved from what I got back from nullmove >>and from the normal process were just a few centipawns in difference. Could this >>be because of search instabillity? If it isn't a bug in my program I had the >>idea to search nullmove with beta-MARGIN in order for the value returned by null >>move to bridge the few centipawns gap. And taking MARGIN the few centipawns. But >>I'm not sure if that is correct. Can someone shine a light on this? > >It can and will happen quite often. The basic problem is when you have an >advantage, wich I will take away from you in a couple of moves. > >ie suppose you have rook on the 7th, wich will be attcked by my knight in two >moves, if you don't move it away I will capture it on the 3rd move. > >If a nullmove search reduces depth enough to not let me make this 3rd move, you >will still get the RookOn7th bonus, wich it would get if you would normaly >search and do reach my 3rd move. > >That's why nullmove hurts positionally (an tacticly). As a compensation, it will >let you search deeper and improve both tactics and positional. If all is well, >the improvement should be higher than the loss. > >Tony > >> >>Thanks, greetings Bert Ok, I spotted some flaws in what I wrote. But I guess it comes down to the postional tactics loss. So the story is null move is hurting positional play, couldn't you then take it to the extreme, if a null move doesn't lose material then you assume your position is ok and return beta? Or if your null move does lose a bit of tactics but not too much. I think that is what you do when you search null move with beta-MARGIN. It speeds up my program when I do that but I am not sure if it is correct. greetings Bert
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