Author: Rafael Andrist
Date: 13:56:45 09/14/03
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On September 14, 2003 at 15:28:07, Dieter Buerssner wrote: >On September 14, 2003 at 05:31:11, Rafael Andrist wrote: >>In a pawnless endgame with DTM-optimal = DTC-optimal play >>with two DTC phases the sum of DTC at the beginning of each phase should equal >>DTM. Similar for DTZ, but more difficult to check. > >I read this a few time, but did not get it. With "DTM-optimal = DTC-optimal": This is only meant for the appropriate counting. The question arises because it is possible in DTC/DTZ to have a situation with a "forced conversion to loss", i.e. the loser must capture a piece or make a pawn step to enter a lost ending and has no other choice. In DTM, this situation does not exist, because the logical equivalent to this would be a player who mates himself, and this is not possible in chess. To answer the question I would simply say that DTM = sum of all DTC in the winning line, but this is of course only true when DTM optimal line and DTC optimal line are the same. One needs to check this only for one crucial position, the other positions are then automatically correct. >What do you exactly mean by the two DTC phases? Two parts/phases in the optimal line, divided by the point where the conversion occurs. In DTZ are several phases possible inside the same endgame. >>I'm sure you aware of this, but note that setting DTZ>50 to a draw after the >>generation process is not very useful as you miss the biggest number of draws, >>because they have DTZ<=50. > >Don't be sure, that I am aware of it :-( Actually, I don't understand what you >mean. How could one miss draws? Of course, probing is a little bit trickier >with the DTZ (especially, when one takes into account, that the opponent will >not play optimal). One has to look at the 50 moves rule counter as well, in >positions, where it is not zero. But at the conversion points (including pawn >pushes) it will always be zero (so, for the generation process, this should be >no problem). If you consequently reset all positions with DTZ>50 to draws _during_ the generation process (BTW, the generation will then take clearly longer) then there is no problem, but if you reset it _after_ the generation process, as I wrote above, you have a serious problem. There may well be a position with DTZ=7 which is a draw, because after that forced pawn step, the next pawn step could be delayed more than 50 moves. If you have some more questions, please email me. [...] >Indeed, that is a big advantage. I had the ambition, to do it fully with own >code. If I had the ambition to create a really strong engine, I would certainly also do this :-) >The main motivation was >the 50 moves rule, that is ignored by all other currently available TBs to my >knowledge. DTZ50 (=DTZ, but taking into account the 50-move rule) endgame tables exist for all 5-men and some 6-men, and they are still growing. The biggest part of them has been generated by John Tamplin. I hope to see you in Graz, some interesting papers about endgame metrics and strategies will be presented at the ACG 10. regards Rafael B. Andrist
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