{"action":"created","issue":{"url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/242","labels_url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/242/labels{/name}","comments_url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/242/comments","events_url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/242/events","html_url":"https://github.com/official-stockfish/Stockfish/pull/242","id":56295154,"number":242,"title":"Correct handling of KQKRPs endgame.","user":{"login":"jhellis3","id":3711245,"avatar_url":"https://avatars.githubusercontent.com/u/3711245?v=3","gravatar_id":"","url":"https://api.github.com/users/jhellis3","html_url":"https://github.com/jhellis3","followers_url":"https://api.github.com/users/jhellis3/followers","following_url":"https://api.github.com/users/jhellis3/following{/other_user}","gists_url":"https://api.github.com/users/jhellis3/gists{/gist_id}","starred_url":"https://api.github.com/users/jhellis3/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jhellis3/subscriptions","organizations_url":"https://api.github.com/users/jhellis3/orgs","repos_url":"https://api.github.com/users/jhellis3/repos","events_url":"https://api.github.com/users/jhellis3/events{/privacy}","received_events_url":"https://api.github.com/users/jhellis3/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":10,"created_at":"2015-02-02T21:23:35Z","updated_at":"2015-02-04T17:00:15Z","closed_at":"2015-02-03T20:41:10Z","pull_request":{"url":"https://api.github.com/repos/official-stockfish/Stockfish/pulls/242","html_url":"https://github.com/official-stockfish/Stockfish/pull/242","diff_url":"https://github.com/official-stockfish/Stockfish/pull/242.diff","patch_url":"https://github.com/official-stockfish/Stockfish/pull/242.patch"},"body":"IIRC, the current code for this endgame was committed following a\r\nparticularly embarrassing TCEC game. The current code is fine in that\r\nprovides correct evaluations for the positions it addresses; however,\r\nthere are holes in its coverage allowing Stockfish to search around the\r\ncode, effectively rendering it useless.\r\n\r\nThese changes effectively fill in the holes the current approach and\r\nalso add specialized knowledge for the unique cases of Rook and Knight\r\npawns which were either being handled incorrectly or not at all.\r\nInspiration for these changes was another game in the latest TCEC\r\nhighlighting the insufficiency of the current code. The specific\r\nposition is the first FEN listed in the notes.\r\n\r\nBench: 9180815"},"comment":{"url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/comments/72893098","html_url":"https://github.com/official-stockfish/Stockfish/pull/242#issuecomment-72893098","issue_url":"https://api.github.com/repos/official-stockfish/Stockfish/issues/242","id":72893098,"user":{"login":"jhellis3","id":3711245,"avatar_url":"https://avatars.githubusercontent.com/u/3711245?v=3","gravatar_id":"","url":"https://api.github.com/users/jhellis3","html_url":"https://github.com/jhellis3","followers_url":"https://api.github.com/users/jhellis3/followers","following_url":"https://api.github.com/users/jhellis3/following{/other_user}","gists_url":"https://api.github.com/users/jhellis3/gists{/gist_id}","starred_url":"https://api.github.com/users/jhellis3/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jhellis3/subscriptions","organizations_url":"https://api.github.com/users/jhellis3/orgs","repos_url":"https://api.github.com/users/jhellis3/repos","events_url":"https://api.github.com/users/jhellis3/events{/privacy}","received_events_url":"https://api.github.com/users/jhellis3/received_events","type":"User","site_admin":false},"created_at":"2015-02-04T17:00:15Z","updated_at":"2015-02-04T17:00:15Z","body":"Not everyone has/uses TBs, I do not.  And by that logic we could remove all endgame knowledge from SF that is less than 6 pieces.  \r\n\r\nThe search already goes wrong in the midgame because SF's eval is by default wrong.  The \"imperfect\" heuristic is both far better than what we have now and far better than nothing.  Hell, the eval itself is nothing more than an imperfect heuristic to guide search (which is why it gets this endgame very wrong).  This comment also tells me you have not downloaded and actually tested the changes, because if you had, you would see that my comment about search correcting the eval quickly is accurate. \r\n\r\nThere is really zero risk here.  If SF is in an antecedent position where it is able to go up a Queen for a Rook if it chooses, it is not going to lose the game, period.  It may, however, draw the game by entering into this endgame which it will not avoid because it can not see it as a draw, as it has done twice in TCEC now. \r\n"}}