Author: Robert Hyatt
Date: 06:22:40 05/13/00
Go up one level in this thread
On May 13, 2000 at 02:39:33, blass uri wrote: >On May 12, 2000 at 23:14:33, Robert Hyatt wrote: > >>On May 11, 2000 at 12:50:39, Graham Laight wrote: >> >>>On May 11, 2000 at 10:43:57, blass uri wrote: >>> >>>>On May 11, 2000 at 10:20:34, Graham Laight wrote: >>>> >>>>>On May 11, 2000 at 10:07:56, blass uri wrote: >>>>> >>>>>>On May 11, 2000 at 08:33:26, Mogens Larsen wrote: >>>>>> >>>>>>>On May 11, 2000 at 05:36:42, blass uri wrote: >>>>>>> >>>>>>>>I also believe that other beta testers did not think about part of my productive >>>>>>>>ideas for chess programs. >>>>>>> >>>>>>>Out of curiosity, what productive ideas have you been suggesting? >>>>>>> >>>>>>>Sincerely, >>>>>>>Mogens >>>>>> >>>>>>I will repeat one idea that I posted here: >>>>>> >>>>>> >>>>>>Many programs are null movers and they prune moves when they see no threat. >>>>>> >>>>>>I found that Crafty could not find some tactics in practical games because it >>>>>>pruned threat mate moves. >>>>>> >>>>>>I suggested that before the decision if to prune by null move to check also if >>>>>>there is a mate threat to bigger depth(If it seach d plies for regular threat it >>>>>>can search d+1 or d+2 plies for mate threat) >>>>>> >>>>>>I think this will help crafty to see tactics when there is a mate attacks and I >>>>>>think that crafty will not be significantly slower when there is no mate threat >>>>>>because checking if there is a d+1 plies mate threat is easier than checking if >>>>>>there is a d plies not mate threat). >>>>>> >>>>>>Crafty can call chest(a free program that is the best mate solver) to check if >>>>>>there is a mate threat and chest is a very fast mate solver(it tries to prove >>>>>>that there is no mate with the smallest possible tree and it helps it to see >>>>>>that there is no mate very fast). >>>>>> >>>>>>I read that it is a slow searcher and search only 20000 nodes per seconds on >>>>>>a slow hardware p166(I am not sure if I am right about the hardware) but it can >>>>>>solve 1500 mate in 2 in one second. >>>>>> >>>>>> >>>>>>Crafty on p166 needs significantly more than 1/1500 second in order to search 3 >>>>>>plys threat when these threats can miss mate in 2 because crafty's evaluation >>>>>>also has no idea if the position is mate so it may need more than 2d-1 plies to >>>>>>see mate in d threat not only because of null move. >>>>>> >>>>>>Uri >>>>> >>>>>This is a good idea, but I don't think Bob will go for it. >>>>> >>>>>Firstly, it's difficult to know whether there's a possible mate threat. If there >>>>>is, there's a high probability that a chess program would stumble upon it >>>>>anyway. >>>> >>>>It is not so difficult to know when there is a mate threat >>>> >>>>There are positions when it is more common when the king is exposed >>>>and it take less time to check if there is amate threat than checking if there >>>>is another threat so crafty will not be significantly slower. >>>> >>>>> >>>>>Secondly, I think Bob likes to control everything that's happening so that he >>>>>can ensure that it's all done in the minimum amount of time. Having a cuckoo in >>>>>the nest doing unpredictable things with unpredictable quantities of resources >>>>>is hardly likely to please Bob, from my readings of his postings over the years. >>>> >>>>It is possible to control the time. >>>>You can decide to call chest to search for a mate threat not more than 1/10 of >>>>the time that you search for other threats(It will often search deeper and even >>>>if it does not search deeper it can see mate threats that the regular search of >>>>crafty does not see because of null move pruning because crafty is using null >>>>move recursively) >>>> >>>>Crafty will be slightly slower in cases when there is no mate threats but the >>>>fact that it will find some important tactics that it did not find before is >>>>more important. >>>> >>>>Uri >>> >>>Perhaps chess programmers will have to accept an "object oriented" approach to >>>programming to make their programs much better - with different programmers >>>doing different objects. >>> >>>I have already stated my case that programmers should consider using knowledge >>>management tools (I suggest http://www.haley.com might be a good place to start) >>>because at least one top programmer has admitted that building the knowledge in >>>a non-systematic way has resulted in the same knowledge being used more than >>>once in evaluating position nodes. >>> >>>I remember in the 1970s when people would build a hi-fi system. They would get >>>the turntable from one supplier, the tape deck from another, the tuner from >>>another, the amplifier from another, and the speakers from yet another! >>> >>>Maybe we have to go this way in building "chess systems" to get the best >>>possible players. >>> >>>-g >> >> >>THe problem here is that null-move searches are done at _every_ node in the >>tree. Now, before allowing a null-move fail high, it would need to do a >>search to detect threats. That would _definitely_ slow it down significantly. > >It depends on the time that you search for mate threats. >If you search for mate threats only 1/10 of the time that you search for regular >threats than it slows it down by less than 10%(I do not know how much because I >do not know how much time does crafty use for null move searches) You are forgetting this is a _tree_. This time is added for a _bunch_ of nodes interior to the tree. It wouldn't just cost 10%. It would probably cost a factor of 2-3 (at least one ply). > >searching for mate threats is clearly more easy than searching for regular >threats so you can see deeper inspite of the fact that you use less time. Not always. Even a mate in 2 can have the first move as a non-check. Now, that 3 ply search for mate is no easier than a normal 3 ply search, since there is no clue that the first move leads to mate... > >Even if you do not see deeper in plies you can see deeper because when you >search for mate threats(by chest) you can see every mate threat and there is no >problem of recursive null move pruning. > >Uri
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