Antichess solution server

HTTP API and C library to query Watkins antichess proof tables. The decompressed proof trees (4.5 GB total) are memory mapped allowing the server to run on systems with as little as 128 MB RAM. Extra RAM may be used by the operating systems page cache for faster lookups.

Building

Install libevent2:

apt-get install build-essential libevent-dev

Then:

make

Usage

Download and bunzip2 the proof tree(s):

wget https://backscattering.de/watkins/e3wins.rev.bz2  # mirror (1.1 GB)
bunzip2 e3wins.rev.bz2

Then start the server:

./antichess-tree-server [--verbose] [--cors] [--port 5004] e3wins.rev

HTTP API

CORS enabled if --cors was given. Provide moves as a GET parameter or as plain text in the POST body. Space or comma seperated.

GET|POST /

> curl https://tablebase.lichess.org/watkins --data e2e3,c7c5,f1b5

{
  "game_over": false,
  "moves": [
    {"uci": "c5c4", "san": "c4", "nodes": 97097576},
    {"uci": "g8h6", "san": "Nh6", "nodes": 38793760},
    {"uci": "d8c7", "san": "Qc7", "nodes": 29352314},
    {"uci": "g7g5", "san": "g5", "nodes": 16120450},
    {"uci": "h7h5", "san": "h5", "nodes": 4057183},
    {"uci": "b7b6", "san": "b6", "nodes": 3781414},
    {"uci": "a7a5", "san": "a5", "nodes": 2574453},
    {"uci": "e7e6", "san": "e6", "nodes": 1663892},
    {"uci": "d8a5", "san": "Qa5", "nodes": 1584198},
    {"uci": "f7f6", "san": "f6", "nodes": 1095973},
    {"uci": "b8c6", "san": "Nc6", "nodes": 687144},
    {"uci": "g8f6", "san": "Nf6", "nodes": 296496},
    {"uci": "e7e5", "san": "e5", "nodes": 294169},
    {"uci": "b8a6", "san": "Na6", "nodes": 262343},
    {"uci": "g7g6", "san": "g6", "nodes": 250949},
    {"uci": "f7f5", "san": "f5", "nodes": 153818},
    {"uci": "h7h6", "san": "h6", "nodes": 124882},
    {"uci": "a7a6", "san": "a6", "nodes": 21336},
    {"uci": "d8b6", "san": "Qb6", "nodes": 3078},
    {"uci": "d7d5", "san": "d5", "nodes": 33},
    {"uci": "d7d6", "san": "d6", "nodes": 31}
  ]
}

C API

#include <stdio.h>
#include <errno.h>
#include <string.h>

#include "tree.h"

int main() {
    tree_t tree;

    if (!tree_open(&tree, "easy18.done")) {
        printf("could not open tree: %s\n", strerror(errno));
        return 1;
    }

    query_result_t result;
    query_result_clear(&result);

    move_t moves[] = { move_parse("e2e3") };
    size_t moves_len = 1;

    if (!tree_query(&tree, moves, moves_len, &result)) {
        printf("query failed\n");
        return 1;
    }

    // Could also query other trees now. Results are merged.

    query_result_sort(&result);

    for (size_t i = 0; i < result.num_children; i++) {
        char uci[MAX_UCI];
        move_uci(result.moves[i], uci);

        printf("%s %d\n", uci, result.sizes[i]);
    }

    return 0;
}

Acknowledgements

Thanks to Mark Watkins, Ben Nye, Catalin Francu and others for solving antichess and publishing the proof trees.

License

Licensed under the AGPLv3+. See COPYING for the full license text.