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README.md

README.md

Overview

Run powerful and flexible queries on very big chessdatabases and with very high speed.

Start building an index out of a PGN file:

./scoutfish make my_big_db.pgn

Scoutfish will create a file called my_big_db.scout with the needed bits to make the queries lightning fast. Queries are written in JSON format that is human-readable, well supported in most languages and very simple. Search result will be in JSON too.

You can run Scoutfish from the command line:

./scoutfish scout my_big_db.scout { "sub-fen": "8/8/p7/8/8/1B3N2/8/8" }

To find all the games that match the given sub-fen condition, i.e. all the games with at least one position with a black pawn in a6, a white bishop in b3 and a white knight in f3. Output will be like:

{
    "moves": 14922,
    "match count": 8,
    "moves/second": 3730500,
    "processing time (ms)": 4,
    "matches":
    [
        { "ofs": 75129, "ply": [11] },
        { "ofs": 80890, "ply": [11] },
        { "ofs": 342346, "ply": [13] },
        { "ofs": 346059, "ply": [13] },
        { "ofs": 375551, "ply": [21] },
        { "ofs": 484182, "ply": [29] },
        { "ofs": 486999, "ply": [29] },
        { "ofs": 536474, "ply": [13] }
    ]
}

After some header, there is a list of matches, each match reports an offset (in bytes) in the original my_big_db.pgn file, pointing at the beginning of the matching game and the ply number: this is the number of (half) moves before reaching the first position in the game that satisfies the given condition.

In case you call Scoutfish from a higher level tool, like a GUI or a web interface, it is better to run in interactive mode:

./scoutfish
setoption name threads value 8
scout my_big_db.scout { "sub-fen": "8/8/8/8/1k6/8/8/8", "material": "KBNKP" }
scout my_big_db.scout { "white-move": "O-O-O" }
quit

Scoutfish is strictly derived from Stockfish so, yes, it understands UCI commands, like setoption, that we use to increase thread number according to our hardware: the search speed will increase accordingly!

Above examples show how to look for a specific material distribution and move and how to compose a multi-rule condition: a position should satisfy all the rules to match the condition.

You are not limited to search for a single sub-fen, the following condition:

{ "sub-fen": ["8/8/8/q7/8/8/8/8", "8/8/8/r7/8/8/8/8"] }

Will find all the positions with a black queen or a black rook in a5. There is no limit to the size of the sub-fen list, enabling to compose very powerful requests.

The position full FEN is just a special sub-fen, so:

{ "sub-fen": ["rnbqkbnr/pp1p1ppp/2p5/4p3/3PP3/8/PPP2PPP/RNBQKBNR",
              "rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R"] }

Will search for all the games with a Caro-Kann or a Sicilian opening.

Rules

Rules allow to look for very specific occurrences in the game. We have already seen some of them, like sub-fen, but there are many more.

result

Find all games with a given result in PGN notation, like "1-0" or "1/2-1/2". Support lists.

{ "sub-fen": "8/pp1p1ppp/2p5/4p3/3PP3/8/PPP2PPP/8", "result": "1-0" }
{ "result": ["1-0", "0-1"] }

To find all white winning games with given sub-fen or all the decided games.

result-type

Find all games with a given result type that can be "mate" or "stalemate".

{ "result": "0-1", "result-type": "mate" }

To find all games won by black by giving mate.

material

Find all games with a given material distribution, i.e. the given pieces, no matter where placed. Support lists.

{ "material": ["KBNKNN", "KBNPKNN"] }

To find all end-games with white Knight and Bishop plus one optional pawn against two black Knights.

imbalance

Find all games with a given material imbalance. Support lists.

{ "imbalance": ["PPPv", "PPv"] }
{ "imbalance": "PPvN" }

To find all games with 3 or 2 pawns advantage for white and all games where white is above 2 pawns but down of a knight.

sub-fen

Find all games with a position matching the sub-fen pattern given in PGN notation. Support lists.

{ "sub-fen": "1n2k1n1/8/8/8/8/8/8/2B1K1N1", "material": "KBNKNN" }

To find all games with given sub-fen and given material distribution. Note that the sub-fen is matched by the start position and without the added rule on material, any game would match. A condition composed by sub-fen + material, can be used to find an exact fen.

white-move / black-move

Find all games with a given move in PGN notation. Support lists.

{"white-move": "e8=Q"}
{"black-move": ["O-O-O", "O-O"]}
{"black-move": "Rac1"}

To find all games with white's queen promotion in e8 and all games with a black castling, no matter if long or short. Rule supports SAN notation with a disambiguation, like Rac1.

moved / captured

Find all games with a given moved and/or captured piece. Pieces are listed in a single string.

{"moved": "KP", "captured": "Q" }
{"captured": "" }

To find all games with a queen captured by a king or a pawn and all games with a quiet move (eventually to be used in a multi-rule condition).

stm

This rule matches the given side to move, that can be "white" or "black" Usually it is used in a multi-rule condition.

{"stm": "black", "captured": "QR" }

To find all games where black side captures a queen or a rook.

pass

This rule matches any position. It is used mainly for debugging purposes or as a part of a more complex condition (see streaks).

{"pass": "" }

To find the number of games in the DB, because it will match any game.

Sequences

A sequence is a powerful feature of Scoutfish to look for games that satisfy more than one condition at different times in game. This is very useful in looking for a piece path from a position. Typical tournament player questions are: how does one maneuver the bishop in this opening, should we go f1-d3-c2 or f1-b5-a4. When should we select which maneuver?

{ "sequence": [ { "sub-fen": "r1bqkb1r/pppp1ppp/2n2n2/1B2p3/4P3/2N2N2/PPPP1PPP/R1BQK2R", "result": "1-0" },
                { "sub-fen": "8/8/8/8/2B5/8/8/8" },
                { "sub-fen": "8/8/8/8/8/5B2/8/8" } ] }

The above sequence will find all the games won by white, with Four Knights Spanish Variation opening and with bishop maneuvering to b5-c4-f3.

A sequence is mainly a list of conditions: a game should match first condition, then the second one (eventually later in the game) and so on for all the list, that can be arbitrary long. Output of the search will be like:

{
    "moves": 28796,
    "match count": 2,
    "moves/second": 5759200,
    "processing time (ms)": 5,
    "matches":
    [
        { "ofs": 19054, "ply": [7, 15, 17] },
        { "ofs": 20653, "ply": [7, 15, 17] }
    ]
}

Where ply list will show the matching ply for each condition in the sequence.

Streaks

A streak is a special kind of sequence. It is defined like a sequence and has all the sequence properties, but it is different in two key points:

  • Conditions in a streak should be satisfied in consecutive (half) moves
  • A streak can appear nested in a bigger, outer sequence

Mainly a streak is like a sequence but with the added constrain that the conditions should be satisfied one-by-one along consecutive moves. You may want to use a streak to look for a white's pawn-down imbalance that should persist for at least few moves to be sure we are not in the middle of a capture-recapture combination:

{ "streak": [ { "imbalance": "vP" }, { "imbalance": "vP" }, { "imbalance": "vP" } ] }

From chess perspective, say you want to find games with a clearance sacrifice in the Benoni for white. Plan of e5, dxe5, followed by f5 and then Ne4 for white. The first three moves are in a streak, but the last move might be delayed by a move (but is also played immediately):

{ "sequence": [ { "sub-fen": "rnbqkb1r/pp1p1ppp/4pn2/2pP4/2P5/2N5/PP2PPPP/R1BQKBNR"},
                { "streak": [ { "white-move": "e5"}, { "black-move": "dxe5"}, { "white-move": "f5"} ] },
                { "white-move": "Ne4"} ] }

The above sequence, first checks for Benoni opening, then checks for the consecutives e5, dxe5, f5 then finally by the (possibly delayed) Ne4.

Some rules like captured are very suitable to be used in a streak:

{ "streak": [ { "captured": "" }, { "stm": "white", "captured": "Q" }, { "captured": "" } ] }
{ "streak": [ { "white-move": "e5"}, { "pass": "" }, { "white-move": "f5" } ] }

To find all games where white captures a net queen, i.e. not in a capture-recapture combination. The second streak uses 'pass' rule to find all games with white e5 followed by f5, independently from the black reply.

Python wrapper

As a typical UCI chess engine, also Scoutfish is not intended to be exposed to the user directly, eventually a GUI or a web interface will handle the user interaction, composing the query and later presenting the results in a graphical form, ensuring a user friendly experience.

To easy integration with higher level tools, a Python wrapper is provided through scoutfish.py file:

from scoutfish import Scoutfish

p = Scoutfish()
p.setoption('threads', 4)  # Will use 4 threads for searching
p.open('my_big.pgn')

q = {'white-move': 'O-O-O'}  # Our query, defined as a simple dict
result = p.scout(q)

num = result['match count']
print('Found ' + str(num) + ' games')

# Run again the query but limiting output to max 10 games and skipping
# the first 50 results. This is useful for pagination.
q = {'skip': 50, 'limit': 10, 'white-move': 'O-O-O'}

result = p.scout(q)
games = p.get_games(result['matches'])  # Load the pgn games from my_big.pgn

for g in games:
    print(g['pgn'])

p.close()
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