CCRL Discussion Board

.

I'm rather out of touch with what has been going on here lately ...

Has anyone done a review of zugzwangs in 5-1 chess, or in any of the 5-1 EGTs?

Info in the next five days will be doubly welcome.

Many thanks - Guy

There is some info at www.icga.org - Game-Specific Info - Losing Chess - on the work done on EGTS for Losing Chess.

John Beasley surveyed what had been done on Losing Chess EGTs, on which 'Angrim' Ben Nye was most recently active.

g

This is an old thread resurfacing. Since it was started, has it not been agreed on this board that building WDL EGTs first is a help in building DTC/M/Z EGTs, since it is not necessary to investigate whether a potential stm-loses position is in fact a loss if it is not. Also, I'm not sure about this...

Sound thinker and reasonable writer: I learned from him, and no Dining Philosophers have died on my watch. Not a man for the 'small talk' though.
See also http://www.cs.utexas.edu/users/EWD/
g

No mention of bitbases (as per Shredderbases) in the Fritz 11 product spec. I guess this is a misnomer for Nalimov databases as accessed by Fritz.
g

Codeman's idea of counting down how many options the 'possible loser' has sounds good in theory - and Ken Thompson tried it, but KT said that it was not a contributor to efficiency in practice. See an old ICCA_J article by or on behalf of Ken Thompson. Faster speed is achieved by: 1) not having to r...

The only generator that is (or was) around is Eugene Nalimov's tbgen ... and I'm not sure how 'current' that was in terms of providing for all the 3-3p and 4-2p endgames. It only works to DTM. Marc B's gtbgen was only circulated amongst a small group, and I'm sure he doesn't intend it to be publicly...

Let us, for the moment, ignore the k-move rule which will really complicate things :-). It is certainly true that if one could have, for each position, a defined loopless, sequence (i.e. lattice) of subgoals ending in mate which can be persistently (i.e. without subsequent regression) achieved, then...

The DTM (Depth to Mate) EGT is publicly available. The DTC (Depth to Conversion) is probably better for learning how to win but is not so available. Neither recognise the 50-move rule but you should not need to for KQKR. http://chess.jaet.org/endings/ gives both DTC and DTM depths for KQKR positions...

Thanks, jm, for the reminder about the shallow missed wins. I never new about the 'Transparent Pawn' bug.
g

[ Maybe I lost concentration once or twice when the 'move counter' idea was being discussed. ] Small point: in reality, we are interested in 'moves needing to be available' rather than move-counter. If I stopped earlier DTM values being overwritten in the 'back-propagate immediately' attempt at a DT...

... which is officially ignored (see the PCCC Codex) in Composition except for Retrograde problems. The 50-move rule has been an interesting challenge - leading to the creation of the DTR/DTZR metric some years ago, some interesting dialogue here, and some corrections to past thinking. If it leads t...

I thought I'd proved that my algorithm for the DTM50 EGT was correct, but the flaw comes right at the end: 1) any 'win/loss in the DTZ50 metric' will be placed, initially in cycle 'dz50', in my 'DTM50' lattice 2) 'DTZ50 draws' will not be placed in the lattice - ever 3) the defender can step down on...

I'm having second-thoughts ... again. While I have described a construction that, provided the two sides play SM50-/SM50+, gives a set of paths through the EGT that decrement DTM by 1 ply each time and take no longer than 100 plies in the phase, it's not obvious that the defender cannot 'bail out' a...

Re http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=6&t=2590, I don't think I 'got to the pitch of the ball' with that question. We eventually decided, I'm sure rightly, that the SZ50oM- strategy (while being the closest strategy given the EGTs I would consider holding) is not th...

I think we are now in an analogous position with DTM50 EGTs to where we are with (DT, DTZR) EGTs. Both positions have a certain irony. szyzygy correctly raised an issue as to whether mb's DTM50 EGTs not only had the same wins and draws as the DTZ50 EGT but also avoided leading the winner into a 50-m...

Thanks, mb: always good to be able to get back to primary sources. I thought DTMk was part of the potential of your gtbgen: we included mention of DTMk in the paper, but I was never interested in having a DTM50 version of gtbgen myself, so don’t know what was actually done in DTM50 terms, or how the...

kronsteen's last contribution is nearly there, but not quite I think ... The 'old way', used by Nalimov et al, was to promulgate (backwards) any available depth 'D' to create a definite win in 'D+1' or a possible loss in 'D' [moves]. This has a major disadvantage, but one advantage which I now appre...

The issue is that there are two ways of retro'ing-back decisive positions: a) the old way - retro-back any and all decisive positions which are to hand, regardless of their depth b) the new way, 'post Wu': retro-back wins/losses in 'n' to define losses/wins in 'n+1' (plies). The old way will I think...

We can leave the 'finite/infinite move-choice' thing to one side for the moment. As this dialogue is continuing longer than I expected, I'm increasingly conscious of the fact that it might be invalidated by wrong assumptions by either of us. A few words from Marc might help. I think I still have his...

I'm quite familiar with the fact that lines that minimax DTM without any k-move rule are not necessarily lines that minimax DTM in the context of a k-move rule. For a start, you can't move to a position that is a draw in DTM50 terms. I've published plenty of examples, found by John Tamplin, where th...

Well, if I have got the definition of mb's DTM50 metric wrong, I hope he will step in and correct me. Yes, I agree that if a position is decisive under a 50-move rule, there is a line that minimaxes DTM. You only need the fact that 'decisive' ==> finite number of moves to win. You don't actually nee...

The '6-man Data and Strategy' paper says that mb extended Nalimov's DTM-code to enable it to generate EGTs to the DTC(k), DTMk and DTZ(k) metrics. I assume mb knew what he meant by these metrics and satisfied himself that the code works - but I have no direct knowledge of any DTMk EGTs existing. My ...

Analogous to the KNNKP and KQPKQ Challenges, on a larger scale, but only involving two phases of play ... Ignoring the 50-move rule, wtm can win 282,912,378 positions: with the 50-move rule, wtm should only win 141,038,155 of these. So 141,874,223 of these positions are affected by the 50m-rule. Non...