Author: Heiner Marxen
Date: 06:37:55 01/07/05
Go up one level in this thread
On January 06, 2005 at 12:59:29, F. Huber wrote: >On January 06, 2005 at 12:20:13, Heiner Marxen wrote: > >>On January 05, 2005 at 16:15:22, F. Huber wrote: >> >>>On January 05, 2005 at 14:02:58, Richard Pijl wrote: >>> >>>>On January 05, 2005 at 13:47:09, Kurt Utzinger wrote: >>>> >>>>>Much too easy for any chess program I think. Or can you find >>>>>a modern engine being unable to solve this within 0 to some seconds? >>>>>Kurt >>>> >>>>I only tried a few, and all were able to solve it in 1 second or less on my >>>>machine. >>>>Now a question for the mate-solvers: Is this a mate in 20, or can a faster mate >>>>be found? >>>>Richard. >>> >>>Hi Richard, >>> >>>I´ve tried it now in brute-force mode with ´Gustav 3.0´ up to depth 13, but >>>with a branching factor of about 2.5 it would take too long, if it´s really >>>a mate in 20 (so at least it´s above 13). >>>Chest (also in brute force) is much slower for this position ... >>> >>>Of course all this is _without_ any EGTBs, since both programs don´t support >>>them - although: Heiner Marxens private development version of Chest seems to >>>already have implemented it, so maybe Heiner could try this problem. >> >>Hello Franz, >> >>I've started it on my Athlon 1500+ with all 3&4 piece TBs, and very few 5-piece >>TBs. Depth 12 needs a minute and shows a factor around 3 between depths, >>so I'm not sure this has any hope. >> >>Which 5-piece tables would be most useful here? >>I could try to get some more... >>[depth 13: 244 secs, factor 3.79... :-( ] > >Hello Heiner, > >I´m not absolutely sure, but I´d guess KNPKP would be the best one (since >white can quite simply force it to remove both queens and win the black knight). I tried to download that one, but failed. Bob's site currently is out of order and the European mirror I tried (ftp://145.94.41.27/Crafty/TB/32p/) does provide not much more than 4KB/s, and after 17 MB the connection froze completely. Just now I have: FEN: 6k1/5Np1/4n3/2Qq2PK/8/8/8/8 w - - analysing (mate in 20 moves): # 1 0.00s 0kN 0.87 1- 0 # 2 0.00s 0kN 1.00 1- 0 # 3 0.00s 0kN [ 5.20] 0.92 30- 0 % EGTB found tables for max 5 pieces % EGTB uses 3728.4K memory internally # 4 0.02s 0kN [ 3.67] 1.07 117- 0 # 5 0.02s [ 1.00] 2kN [ 3.82] 1.51 317- 0 # 6 0.07s [ 3.50] 11kN [ 6.22] 1.82 1444- 0 # 7 0.23s [ 3.29] 51kN [ 4.51] 2.34 5591- 0 # 8 0.94s [ 4.09] 243kN [ 4.76] 2.90 22069- 0 # 9 3.07s [ 3.27] 726kN [ 2.98] 3.31 70315- 0 # 10 6.83s [ 2.22] 1559kN [ 2.15] 4.02 155844- 1 # 11 20.39s [ 2.99] 4502kN [ 2.89] 4.74 429776- 12 # 12 64.43s [ 3.16] 13345kN [ 2.96] 6.58 1143927- 2685 # 13 244.35s [ 3.79] 48544kN [ 3.64] 8.60 3750376- 1285851 # 14 889.90s [ 3.64] 179343kN [ 3.69] 9.96 13432518- 10933117 # 15 3422.06s [ 3.85] 670844kN [ 3.74] 12.51 47288122- 44788721 # 16 14485.35s [ 4.23] 2862927kN [ 4.27] 12.36 193945070- 191445669 # 17 59920.91s [ 4.14] 12006250kN [ 4.19] 12.45 801825148- 799325747 >Of course 6-men TBs would be still better, but probably they are not supported >yet in your current version. (?) >But IMO this is much more a position for a normal chess engine (and EGTBs) than >for a mate solver, and (again only IMO) I don´t really see the need of EGTB- >support in a mate solver at all - there are much too little positions which >would profit by it, but OTH it will probably slowdown the search. > >What´s really surprising with this position, is that Chest is much slower than >Gustav here (which is absolutely not usual!), and furthermore that the branching >factor in Chest is significantly higher than that of Gustav (being about 2.5)!? Obviously, the branching factor causes the slowness (not vice versa). And Chest's worse branching factor most probably is due to its selection of defender moves. While Chest is not naive about this, it is far from perfect, and sometimes a bit of "luck" is involved, also. For a more detailed explanation we had to compare the search trees of Chest and Gustav in more detail. But when Gustav's branching factor here is as good as 2.5 there should be a good chance to have Gustav complete depth 20, right? Have you tried? >Regards, >Franz. Cheers, Heiner
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