Losing Chess Wikipedia page on Losing Chess ======================================================================== Solving Status The move 1. e3 has been solved as a win for White under both FICS and International Rules. The final leg was actually much easier than expected, as I wasted around a year on false leads. In fact, the not-too-deep idea 1. e3 b6 2. a4 e6 3. Ra3 Bxa3 4. Nxa3 Qh4 5. a5 bxa5 6. Qh5! leads to some queen races where White just needs a bit deeper search to show a good score, and the proof only took a few hours (128 cores). The largest part of 1. e3 b6 remains 1. e3 b6 2. a4 e6 3. Ra3 Bxa3 4. Nxa3 b5, and the 2... b5 lines are also quite nontrivial. However, both of those were done in August 2015, a few months after the 2. a4 idea was first tried. This email (or a small variant) was circulated to a number of associated Losing Chess mailing lists, some for programmers, some for aficionados, or mathematics colleagues, or interested chess (grand)masters, ... Some effort was made to reduce the original proof size, and eliminate overly complicated sequences of reversible moves. The revised proof is here, and the online browser is currently here. NOTE: The Browser will likely be terminated in Dec 2019 or soon after. NOTE (7 Jul 2017): Some of the older now-unused files (linked on some pages) were deleted off the web server for reasons of space. If you really want one, I probably still have it on a local hard drive. (15 Apr 2019): As pointed out by Anatoli Shmarlouski, there is a bug in the tablebases. Namely the position with White pawns on f5/g2 and Black pawns on f4/h4 is scored as a Win, even though there are no winning moves. The issue seems to be with the double en passant after g4. This position actually occurs in the 1. e3 c6 solution. There appear to be 40 positions in e3wins.rev2 that are affected by this (in fact, the above position is actually also reached after 1. e3 b5). I think every file except the "easy" wins and 1. e3 e6 was affected. Five TBs used in e3wins.rev2 proof were wrong, but as Klaas Steenhuis points out, other 4-piece TBs are also incorrect. The new revised proof is on the revision page, and a new source tarball is also available. ======================================================================== Status report Losing Chess: 1. e3 wins for White (PDF, short form) Appeared in ICGA Journal 39/2. Losing Chess: 1. e3 wins for White (Oct 2016) (PDF, 240K, 18 pages) (Old versions) Status report (Aug 2014) (PDF, 115K, short form, ICGA Journal 37/2) Status report (Aug 2013) (PDF, longer, with positions) Status report (Sep 2012) (PDF, longer, with positions) ======================================================================== News 10 Oct 2016: 1. e3 b6 is solved. Sorry it took so long... See Page for 1. e3 b6 for (old) news. As with e6, the main thing was to try a different line, here 5. a5 bxa5 6. Qh5! refutes 2. a4 e6 3. Ra3 Bxa3 4. Nxa3 Qh4, though one needs to obtain a good resolution of the races with queen captures to see the endgames are won. I had tried 5. h3 instead, which in the end (and only retrospectively) was a fool's errand of 14 months. Also, I could never get 2. Ba6 to work, and instead 2. a4! (a surprise to many) was the move that worked. Total tree size is 491933802, including 2... b5 at 137.9 million nodes, and 2. a4 e6 3. Ra3 Bxa3 4. Nxa3 b5 with 269 million nodes. 12 Feb 2015: 1. e3 c5 is solved. See Page for 1. e3 c5 for old news, and for partial proof trees. As explained there, in the critical line 19. g3! needed to be tried, while the try Nd1 looked decent for quite some time. Total tree size is 228501054. 13 Aug 2014: 1. e3 e6 is now solved. See Page for 1. e3 e6 for old news. The main thing was to switch to 8. Qxf7!, which I think had been underestimated (both by me and others). Much time was wasted in the other lines. 2013: Significant rewrite with "ClusterGUI" (and as the name might imply, a cluster of 128 or so cores was typically used from then on), and also to handle transpositions into known wins more cleanly (without this, 1. e3 e6 is probably too hard). Sep 2012: 1. e3 b5 is solved. Catalin Francu responds that he had recently solved 1. e3 Nh6 in a week when testing a new laptop for speed. Fortified by this knowledge, 1. e3 g5 is quickly solved too (Francu pointed out that 2. Ba6 bxa6 was won, which led to me looking at this rather than 2. Bd3). early 2012: Inspired by suicidechess.ca (Carl Lajeunesse) and Nilatac (Francu), work starts. 1. e3 c6 is re-solved. 1. e3 Nc6 is solved. ======================================================================== Source code source tarball (1MB) (Linux-based) (Apr 2019) Fixes TB_populate.c with double en passant. Also TB_index2.c now is ep-compliant (was merely cosmetically wrong before). Finally, verify_win.c gives a bit more information on a TB result failure. (Jan 2020) No real changes, make quickstart.sh link LCTB. ======================================================================== Proof trees (with md5sum of bz2 file) easy12.done.bz2 (1.5MB) 5d7fede37dafc29509ef7cf118574334 e3c6.done.bz2 (2.3MB) 382021495d0d34403fe2d4dc22c815b2 e3Nc6.done.bz2 (13MB) 00c913623d16c7892833b65ca28b36e3 e3Nh6.done.bz2 (20MB) 417b33f08fd90afa017931e2ed9cde48 e3g5.done.bz2 (54MB) 1f6fee7a9d0acfa3c1c3fb5cdc21da26 e3b5.done.bz2 (103MB) 4fe3f64fae21247092499dd8263fe4f7 e3e6.done.bz2 (63MB) 54149388cd3fca7b84f867e846e5a3a0 e3c5.done.bz2 (289MB) 65f52983aa0b99444c1e7c799943b223 e3b6.proof.bz2(740MB) d19df1d18518c7a216b44a1e878550cd Warning: this last file will not load in 32-bit Windows WinningGUI. See the 1. e3 b6 page for a splitting into smaller parts. The b6 proof will probably also be revised somewhat in the next few days (when the word "done" might replace "proof" in the filename). Here is everything but c5 and b6 in one file: easy18done.bz2 (254MB) 45ae6e978ad4e9c64934ae6e8e940c42 1. e3 c6 was first solved by Ben Nye in Feb 2003, and 1. e3 Nh6 was first solved by Catalin Francu soon after I told him of my 2012 solving of 1. e3 b5. There is also the revision project that is aimed at producing "better" solutions. ======================================================================== Miscellany Page for proof lines Page about tablebases ======================================================================== White moves that lose The Sep 28 (2014) update contains the ability to have "NULL" moves. This was to expedite some proofs asked for by Klaas Steenhuis, most notably 1. h3 and 1. b4 (which appeared reversed as 1. NULL h6, etc). [He has more recently shown that Black wins both 1. c3 e5! and 1. f3 e6]. h3.LOST.proof.bz2 (5.3MB) 889dcb5385118405109a0b0038f9eba3 b4.LOST.proof.bz2 (19MB) fca952417d69964be773a9883b29cd58 Note: These files are "inverted" and thus break the verifier. They can be uninverted with "./proof_invert uninvert FILENAME" Here are the latest solved lines by Klaas, which he asked me to put here. c3.LOST.proof.bz2 (9.8MB) 829c2ff9cefa3fc93b10e41f5da4db43 c3e5.rev.bz2 (8.5MB) 00fb6e80d2a303e13f155143beb595bf (Jul 2020) Oct 7 (2015): Klaas has solved 1. a3 e6 as a win for Black. He also has simplified 1. f3 d5! by a significant margin over 1. f3 e6. a3e6_rev_new.proof.bz2 (250MB) c5b5971331aa01cef46974347eb302fc old_f3d5_rev.proof.bz2 (18MB) 5a48582282beda9a29c3d45e721fd36d (Jan 2020): versions that fix the double-ep bug are now provided above. Jan 17 (2016): Klaas has simplified the b4 proof. b4.new.LOST.proof.bz2 (7.9MB) 7b0b0c67da856b68e4b8153b59f74a1b Feb 23: Some reduction (from Klaas) of the 1. f3 d5 proof. f3d5_new.proof.bz2 (14MB) 15e50e95b4207880f47615903cbeb996 ======================================================================== Windows usage For Windows users, thanks to Klaas Steenhuis I have a RAR file that contains Java classes and the proof tree parser. LOSING_CHESS32.rar (145K) 91ca08bee3d6bd585618ff6a0d03b207 LOSING_CHESS64.rar (145K) 11c14dd41adc36f96b64adeda8d5c934 The "32" version is for 32-bit Windows, and "64" for 64-bit Windows. I have not tested the latter, and it should only be necessary for proof files larger than about 250 million nodes. First you need to have the Java Runtime environment installed. Then you will need to expand either the above LOSING_CHESS32.rar or LOSING_CHESS64.rar archive, putting all files (.class files, PARSE_WIN.exe, and MERIFONT.TTF) into a directory named C:\LOSING_CHESS (this is so that Java knows where the .exe file is -- I can make a FileChooser for it, but it seems overkill). Then you should be able to open a Command Prompt, change directories via cd C:\LOSING_CHESS and then run the Java applet with java WinningGUI It should bring up a FileChooser, which is a loader for the proof tree. However, this FileChooser fails for me sometimes, and it is probably better to move the desired proof file (say easy12.done) to the C:\LOSING_CHESS directory, and run via "java WinningGUI easy12.done"