Author: Robert Hyatt
Date: 20:15:33 05/13/00
Go up one level in this thread
On May 13, 2000 at 21:12:21, blass uri wrote: >On May 13, 2000 at 18:02:13, Robert Hyatt wrote: > >>On May 13, 2000 at 16:49:59, blass uri wrote: >> >>>On May 13, 2000 at 16:30:27, Robert Hyatt wrote: >>> >>>>>I understood that the idea behind chest is that it has not to try all the ply=1 >>>>>moves to find that there is no mate in 2(it is obvious for mate in 1 when you >>>>>need to generate only threat king moves but I understood that it is also >>>>>possible to do it for mate in 2). >>>>> >>>>>Chest knows for every piece the squares that it controls so it knows the squares >>>>>need to be controled in order to do mate. >>>>> >>>>>If it is obvious from the starting position of the pieces that they cannot >>>>>control the relevant squares in 2 moves then you can discover that there is no >>>>>mate in 2 without generating moves. >>>>> >>>>>Uri >>>> >>>> >>>>what about zugzwang??? >>> >>>chest proves that there is a no mate without really executing the moves and it >>>does not do errors in zugzwang positions. >>> >>>I understand that it does not assume no move for the defender but assumes a >>>simple strategy(king move if possible) and try to prove that the squares cannot >>>be controled in 2 moves by the attacker. >>> >>>Uri >> ><snipped> >>In my case, I need to know that there is a forced mate at the current position, >>so that the null-move won't be tried. There are lots of zugzwang mates where >>you have to confirm that no matter what you do you get mated, even if you are >>not in check. And if you do nothing, you don't get mated instantly. >> >>I am trying to point out that (a) the test is very expensive because it has to >>be done so many times > >I agree that the test has to be done many times but many times a small number is >not very expensive if the number is small enough. > Confucious say "if you multiply a big number times anything, you get a big number." :) I can add a single if statement and see the NPS change. If I add it in the right place... >The number of times you need to do the test is exactly the number of times that >you find that there is no threat and if the time that you need to discover that >there is no mate in 2 is 10 times smaller than the time that you need to >discover that there is no 3 ply threat then you can earn important information >because you sometimes can miss mate in 2 in searching for 3 ply threats because >of null move pruning or by the fact that the evaluation does not know that a >position is mate. I don't do any "threat" detection of any kind. When I enter a new node, I try a hash probe, followed by a null-move search to see if I can exit quickly. I don't do any kind of 'searching' or 'analysis' to determine if a null-move is safe to try... > >I think that searching for mate in n by chest is usually clearly faster than >searching 2n-1 plies forward by crafty. > >Uri I wouldn't be surprised at all. Finding mates is far easier if you are only looking for them and not trying to play a real game... But the question is still how much does it cost. I like the relatively simple search I am using. as simple -> bug-free. Yes, I wish it could do some things quicker. It will when I take the time to get the singular extension stuff implemented...
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