Author: Robert Hyatt
Date: 14:22:48 10/04/01
Go up one level in this thread
On October 04, 2001 at 14:47:56, Uri Blass wrote: >On October 04, 2001 at 14:23:21, Robert Hyatt wrote: > >>On October 04, 2001 at 00:26:38, Uri Blass wrote: >> >>>On October 03, 2001 at 11:30:56, Robert Hyatt wrote: >>> >>>>On October 03, 2001 at 09:58:48, Uri Blass wrote: >>>> >>>>>On October 03, 2001 at 09:47:04, Chessfun wrote: >>>>> >>>>>>On October 03, 2001 at 08:58:28, Uri Blass wrote: >>>>>> >>>>>>>I do not understand some draw decisions >>>>>>> >>>>>>>For example the following position from bringer's game in the last round: >>>>>>> >>>>>>>[D]8/2R5/8/6K1/1k6/7p/6bP/8 b - - 0 107 >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>>>>>> >>>>>>>The last capture was at move 96 and I am not sure if white cannot win this >>>>>>>position >>>>>>> >>>>>>>If white can get the following position in the game then it seems to me that >>>>>>>black is losing(I do not have the 5 piece tablebases of KRP vs KB and someone >>>>>>>with these tablebases can probably say even that it is a forced mate and exactly >>>>>>>the number of moves. >>>>>>> >>>>>>>Uri >>>>>> >>>>>>It's mate in 21, but I can't see how White can force black into this position >>>>>>within 18 more moves. >>>>>> >>>>>>Sarah. >>>>> >>>>>I also cannot see and the original position may be a draw with exact game >>>>>If someone decide to build the 6 piece tablebases for 4 pieces with blocked >>>>>pawns(white pawn at h2 and black pawn at h3) we may know. >>>>> >>>>>Maybe it is a good idea to tell chess programs to build these tablebases during >>>>>a game when the hardware is fast enough and it is tournament time control. >>>>> >>>>>It may be a very good option for correspondence games even today. >>>>> >>>>>Even if programs need 30 to build these tablebases it may be possible to do it >>>>>at some tournament time control games when this kind of position is in the root >>>>>and the program may use 30 minutes for one move but later play always from the >>>>>tablebases. >>>>> >>>>>Uri >>>> >>>> >>>>Did you mean 30 minutes or 30 hours? 30 hours would be very fast for a 6 >>>>piece file. With pawns, maybe 30 days. >>> >>>I did not suggest to generate the full 6 piece tablebase of KRP vs KBP but only >>>the tablebases for the case when the white pawn is at h2 and the black pawn is >>>at h3. >>> >>>the number of relevant positions to investigate is bounded by 31*61*60*59 in >>>this case >>> >>>31 possibilities for the black bishop(it cannot be at h3 because there is a pawn >>>there) >>>61 possibilities for the white rook after putting the bishop >>>60 possibilities for the white king after puting bishop and rook >>>59 possibilities for the black king. >>> >>>Positions after a capture are known by the 5 piece tablebase so we do not need >>>to investigate them. >>> >>>Uri >> >>That is just one case. There are _many_ others with blocked pawns. > >The point is that in a game you need only one of them. > Yes... and some of them are _very_ difficult to compute. They aren't going to finish in 10 minutes or whatever length of time you have to choose a move. More like 2-3 minutes in reality... > > IE >>let's make this a KQP vs KRP ending. With the pawns blocked. It turns into >>a KQ vs KR for tablebase generation purposes. That takes a while... IE it >>isn't computed in 1 minute or 10 minutes because there are so many iterations >>to do, and the size of the temporary files are _still_ big... >> >>I don't think computing them on the fly is doable. It takes over 2 hours >>just to compute all the 4 piece endings by themselves... > >Yes, but you do not need to compute all the 4 piece tablebases but only >something that is sligthly harder than computing one of them(slightly harder >because it is impossible to use symmetry considerations when there are pawns). > >if you need 30 minutes to calculate it then it may be possible in a game if you >have 1 hour for the rest of the game. > >I also expect the time to get smaller in the future. > >I believe that it is also possible to build all the 6 piece tablebases with >blocked pawns in the near future and it may be even a better solution(the number >of possibilities for blocked pawn when you do not consider symmetry is only 20 >so for every material structure building the tablebase is similiar to building a >5 piece tablebases) Some of the 5's take days. SOme take weeks... > >The number of material structures is not big and even smaller than the number of >material structures for the 5 piece tablebases because 4 pieces are known(2 >kings and 2 pawns and you only need to choose 2 more pieces(white and black if I >assume that KPXX vs KP is usually not interesting) > >The number of interesting material structures when you know that 2 pawns are >bloacked is exactly 15 > >KPP vs KPP >KPN vs KPP >KPB vs KPP >KPR vs KPP >KPQ vs KPP >KPN vs KPN >KPB vs KPN >KPR vs KPN >KPQ vs KPN >KPB vs KPB >KPR vs KPB >KPQ vs KPB >KPR vs KPR >KPQ vs KPR >KPQ vs KPQ > >Uri
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