CCRL Discussion Board

Indexing scheme must be kept free, but if cutting TBs in pawn slices is really the only sensible solution for best performance, then so be it. I don't intend my remarks as hard requirements, but as ideas of how to get optimally functioning tables (so I might strictly speaking be off-topic). I think...

But a reason why one might go WDL(50) some way before kpppkpp, at which point one goes DTZ(50) is that ... with a 'sliced-EGT' index ('placing' both sides' Pawns first), the endgames with fewer Pawns have bigger slices. This means that the indivisible KQRNKQR woudl be very inconvenient to do as DTZ...

Hmmm. It is not just because DTZ is small that winning line is easy to find. In kqpkq for example, preliminary required wq moves before touching the pawn in order to preserve a difficult theoretical win thereafter are sometimes rather mysterious, and even at DTZ depth of 3 or 4 one can easily go as...

You understand a1-d1-d4-a4, which means you understand that a chess position without pawns "does not change" if you flip the board horizontally or vertically. Now observe that a chess position without pawns does not change either if you mirror the board in one of the two diagonals a1-h8 an...

But I'm not sure how that helps much, as you'll need the subtables in DTZ50 if you want to use kpppkpp in DTZ50. Wrong. DTZ(50) needs only WDL(50) for daughter endings, not DTZ(50). That's exactly what I wrote: I think the idea is that to generate kpppkpp in DTZ50, you only need all subtables in WD...

However one important advantage of WDL50 is that it allows to construct a DTZ50. So if I want kpppkpp in DTZ50 I have to generate all the necessary WDL50 tables first. This is the reason why I am going to contribute my CPU time towards WDL50 generation when the generator will be available. Are you ...

However one important advantage of WDL50 is that it allows to construct a DTZ50. So if I want kpppkpp in DTZ50 I have to generate all the necessary WDL50 tables first. True, but having kpppkpp in DTZ50 is useless if you don't have the subtables in DTZ50. And if you have the subtables in DTZ50, it i...

Yes, this was addressed in the dtx thread. In border cases a winning position can be drawn by a delay of a single ply, or a 50-move rule draw can be lost by a speed up of a single ply. In these border cases dtz50 must be known in plies, so that optimal moves can be distinguished from moves that are ...

Technically speaking, there is a big difference between the first case, which is a technical limitation (when constrained to use WDL and not DTZ due to space storage limitations, you simply have no way to access perfect 7-men play) and the second one, which is wrong use of knowledge (WDL50 when in ...

I'm sure that if you gave a human a choice between say KQRRKQR or KRK, they would pick the latter every time. Most humans would trade or sacrifice in a heartbeat if it led to a known winning position. The difference is that the computer has a lot more 'known' won endgames. Yes, and a computer as wh...

WDL or WDL50 tables can’t prevent KK’s scenario (engine starting from a won position but going in circles and finally conceding 50-move rule draw) from happening. This is due to lack of “winning line” info. This is the reason why DTZ or DTZ50 info is also needed for “not clear-cut” endings. Yes. An...

Most of tables will be generated in WDL or WDL50 first. Then, some important tables will be generated in DTZ or DTZ50, by those who want them. Having a mix of DTZ and WDL is the unique and strong point of our approach. WDL files are easy to exchange and store. We won't be able to afford massive DTZ...

Lutz Neweklowsky wrote:my mate in 530 is completely generated to DTM ( not only to DTC ) on my pc , and so there doesn`t exist a shorter solution.

Did you write a program that minimaxes DTM over all winning lines that start from your position?

(I did not do KRKEE, because there would be too many unnatural combinations of Elephants to make that meaningfull. With 8-fold symmetry reduction, there are still 2 different kinds of Elephants, only one of which can occur in a Shatranj game. So even with only one Elephant, the results are contamin...

So what would it be used for? Evaluating possible future positions in the computers search tree? Exactly. WDL50-tables are much smaller, which means they can be probed faster (e.g. because more positions can be cached in RAM). Once the position on the board is in the tablebases, the engine will nee...

notnale wrote:By the way, what exactly, does a WDL50 table store?

A WDL50-table stores for each position a W, a D or an L, giving the outcome of the game under optimal play by both sides assuming move-counter = 0 (and taking into account the 50-move rule).

A position can convert with either a black or white move so the exact number of half-moves might make a difference. I know, and this means that it is required to be able to determine dtz50 as number of plies. If both wtm- and btm-tables are available, then these tables can store dtz50 as number of ...

Perform 1 ply and probe the table again. By definition, the position after 1 ply is d-1 plies from a zeroing move. The value returned by the table for that position is either k or k-1. This isn't true if the ply was a zeroing move True, but if you can convert right away to a winning position (or if...

To go back once more to your earlier question: Why not go farther and only store every fourth or every eigth ply? Maybe you meant: why not store each value as a multiple of four or eight plies? (Storing values as a number of full moves is the same as storing values as a multiple of two plies, i.e. s...

I was talking about the whole only store every other ply thing If you only store every second ply, the computer will have to search an extra ply deep at runtime. In any line of play, all odd plies will be played by the same side and all even plies will be played by the other side. That is why it is...

- Code must be capable of generating WDL (or WDLk) tables without having to build DTZ (or DTZk) tables first. Since DTZ (or DTZk) tables can be built off WDL (or WDLk) subtables, this requirement will always be fulfilled: a generator for DTZ/DTZk can be modified to generate WDL/WDLk in a trivial wa...

Why not go farther and only store every fourth or every eigth ply? Because there is no way to tell whether a position occurs in a fourth or eigth ply. It is very easy to tell whether a position has white-to-move (wtm) or black-to-move (btm). That is why it is possible to store only values for posit...

sz: I am not following why you think there is a problem with generating the (DTR, DTZR) EGT - though it's entirely reasonable that you find it difficult to see clearly how it is generated. It is quite clear to me how the generation works, both with the "DTZ-method" and with the "DTM-...

notnale wrote:Ok, I'm convinced now that full moves aren't sufficient

My last post should convince you that they are sufficient

Counting in full moves in DTZ50 should be sufficient to find out whether a position can be won or not with ply-counter = even . By far the most important is the case ply-counter = 0, i.e. the first probe after entering the table (assuming both the wtm- and the btm-table are present). Counting in ful...