CCRL Discussion Board

Zugzwang marking should be fixed now. So now there are no zugzwangs in the 5-man MaxDTM line, but there is one in the 6-man maxDTM line, on move 25.

"☉" - Move leads to a mutual zugzwang. Then there is a serious bug... Look at the 5 pieces maxDTM. 1.Rb3 doesn't lead to mutual zugzwang, black just captures the rook. Probably you have marked with circles the positions with different outcome if WTM and BTM. Only a small percentage of the...

Forbidden You don't have permission to access /chess/4x4-chess/ on this server. Thanks for testing!! OK, this one is fine for now, as the "home" page does not exist yet. 2rp/k1N1/2R1/K3 w - - 0 1 1.Na4?? Rxc2☉!! 2.Nc3 Rc1+ 3.Nb1+□ 3.Nb1+□ ?? Looks OK to me? "□" means the only po...

Arpad Rusz wrote:Nice! What are those circles and squares?

Sorry, I know it's confusing, I should add the notation legend soon. In the meantime:

"□" - The only possible move
"♢" - Winning move, which has equally good alternatives.
"☉" - Move leads to a mutual zugzwang.

I'm testing the 4x4 chess database interface, any help with testing will be appreciated. It's still buggy and lacks features. Some maxDTM positions as examples: 5 pieces, mate in 33 6 pieces, mate in 52 (although any position can be queried by putting a proper FEN into the address line). Notation ex...

Compactness of different metrics: http://kirill-kryukov.com/chess/various/4x4-ULP-per-Byte-7-pieces.png All compressed. 2 metrics in 3x4 (3 to 12 pieces), 4 metrics in 4x4 (3 to 7 pieces). Some observations: - DTM is around 3 pos/byte in both 3x4 and 4x4, slightly more compact in 4x4. - The gap betw...

Database sizes for 3x4 and 4x4 chess. http://kirill-kryukov.com/chess/various/4x4-DB-Size-7-pieces.png "raw" means uncompressed, the rest are all compressed (2 metrics on 3x4 and 4 metrics on 4x4 board). Board occupancy means how large area of the board is occupied. e.g., 3 pieces on 4x4 b...

By the way, do you know how many unique legal positions are possible with 5 pieces in this variant? (Also with 2, 3, 4 pieces).

Interesting comparison, thanks for posting! How do you compute the AverageDTM? Is it for all positions, where draw counts as 0, or only for won/lost positions? I'm curious to compute the AvgDepth in my variants. MaxDepth tables look beautiful, I wonder how to do the same with 6 pieces, 7, 8... Or in...

Since there are no more guesses, here is the summary of currently known 4x4 chess MaxDepth values, compared with all known values from 3x4 and 3x3 chess: http://kirill-kryukov.com/chess/various/4x4-MaxDepth-up-to-7-pieces-1.png Yes, 52 moves DTM with 6 pieces, 54 with 7 pieces. (I still did not walk...

Yes, the wK can be shifted to c1,d2, or d3 and after 1.Kc2 the result is the same as in (Kd1,Pb1/Kb4). So probably these are the other 3 maximum length positions: (Kc1, Pb1/Kb4), (Kd2, Pb1/Kb4) and (Kd3, Pb1/Kb4). (Kc1, Pb1/Kb4) is only mate in 9, throuhg 1.Kb2. The other two are wins in 12. So one...

Does anyone know how I could obtain a program that can calculate tablebases where other pieces are treated as kings, like a 2-man tablebase where the goal is simply to stalemate/checkmate the other piece. Solving variants with fairy piece and exotic rules is exciting topic. Currently my resources a...

Arpad Rusz wrote:This was my position: (Kd1,Pb1/Kb4 12#). Sorry for the wrong coordinates.

Great, yes, this is 12#! According to the database, there are 3 more wins in 12 in kpk. (Unique positions, not just reflections).

Do you have the rights to distribute those books? It's not clear so I'm removing the link for now. Welcome to the forum!

Status update. 7-piece DTM verified OK, 8-piece DTM computation is underway. 3-to-5-piece DTC and DTZ tables are built and verified with no errors.

Hi Arpad! 3 men pawnless tablebases: the KR/K endgame has the longest line. Maximum DTM probably 8. (Ka1,Rd4/Kc3) Yeah, of course KRK for pawnless, however maxDTM is only 7 moves. "Ka1,Rd4/Kc3" is one of those mates in 7: "3R/2k1/4/K3 w - - 0 1" 1.Ra4 Kb3 2.Ra2 Kc3 3.Ra3+ Kc2 4.K...

Finally I have a seemingly functional 4x4 chess solver - that is, it can build DTM tables which pass verification. It's very rough bare solver, no compression, no other metrics, no mining, no stats, no web-interface, etc.. It's full of debugging code, and I did not even begin optimizing for speed. S...

Of course there is no point in trying to push people in directions they don’t want. But releasing a code and letting uncoordinated people do what they want for themselves isn’t probably best either. Agreed. I've been advocating for coordinating the efforts for a few years now, in both sharing and c...

I added DTZ and DTC into the requirement specs draft. DTZ - for symmetry with DTZ50. It allows to skip uninteresting endgames by solving them in WDL, and only solve interesting ones in DTZ. DTZ50/WDL50 allows to do this with 50-move rule, so DTZ/WDL combination will make the same strategy possible f...

Basically, EGTBs is a two-dimensional space, with positions and metrics. To raise new knowledge, one can concentrate the effort in one direction, exploring more complex endings on simplest metrics (7-men WDL(50)) or more complex metrics on simplest endings (3-5 men DTM50/DTR). One can also make a “...

Regarding the idea of everyone focusing on just WDL and not WDL50 (or vice versa), I'm not sure. I think there is no necessity to impose any order on the community, and just let everyone enjoy building the tables in his favorite metric. Eventually the whole 7-piece solution should be complete in bo...

I like the idea and already sponsored the project with a symbolical amount. I see two challenges: 1) You have to attract a programmer who likes the challenge. 2) You have to have the hardware necessary to produce the tables. 3) Distribution (which I don't discuss here because once the tables are th...

I think it would be nice if the demand for speed is lax as it is much easier to implement something when you are allowed to be half as fast as optimum, and more laxity gives more ease. I think the question is: With the project that will run for years (generating the tables), do we want a generator ...

I did not hear about md5summer problems before, but I've seen here reports of problems with some windows builds of md5sum. I wonder what is the cause for these issues, considering how trivial md5 calculation is. Among those that work fine I can also recomment fsum.

No misunderstanding. When I mentioned simultaneous WDL + WDL50 generation, I am assuming two totally independent processes. However, now that I think about it, perhaps generation can be speeded up if the same table is already available in a counterpart metric. But this is not too important optimizat...