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Last active January 31, 2024 02:21
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Test positions for debugging chess engines. Formatted as JSON array of FEN strings
[
{
"depth":1,
"nodes":8,
"fen":"r6r/1b2k1bq/8/8/7B/8/8/R3K2R b KQ - 3 2"
},
{
"depth":1,
"nodes":8,
"fen":"8/8/8/2k5/2pP4/8/B7/4K3 b - d3 0 3"
},
{
"depth":1,
"nodes":19,
"fen":"r1bqkbnr/pppppppp/n7/8/8/P7/1PPPPPPP/RNBQKBNR w KQkq - 2 2"
},
{
"depth":1,
"nodes":5,
"fen":"r3k2r/p1pp1pb1/bn2Qnp1/2qPN3/1p2P3/2N5/PPPBBPPP/R3K2R b KQkq - 3 2"
},
{
"depth":1,
"nodes":44,
"fen":"2kr3r/p1ppqpb1/bn2Qnp1/3PN3/1p2P3/2N5/PPPBBPPP/R3K2R b KQ - 3 2"
},
{
"depth":1,
"nodes":39,
"fen":"rnb2k1r/pp1Pbppp/2p5/q7/2B5/8/PPPQNnPP/RNB1K2R w KQ - 3 9"
},
{
"depth":1,
"nodes":9,
"fen":"2r5/3pk3/8/2P5/8/2K5/8/8 w - - 5 4"
},
{
"depth":3,
"nodes":62379,
"fen":"rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 8"
},
{
"depth":3,
"nodes":89890,
"fen":"r4rk1/1pp1qppp/p1np1n2/2b1p1B1/2B1P1b1/P1NP1N2/1PP1QPPP/R4RK1 w - - 0 10"
},
{
"depth":6,
"nodes":1134888,
"fen":"3k4/3p4/8/K1P4r/8/8/8/8 b - - 0 1"
},
{
"depth":6,
"nodes":1015133,
"fen":"8/8/4k3/8/2p5/8/B2P2K1/8 w - - 0 1"
},
{
"depth":6,
"nodes":1440467,
"fen":"8/8/1k6/2b5/2pP4/8/5K2/8 b - d3 0 1"
},
{
"depth":6,
"nodes":661072,
"fen":"5k2/8/8/8/8/8/8/4K2R w K - 0 1"
},
{
"depth":6,
"nodes":803711,
"fen":"3k4/8/8/8/8/8/8/R3K3 w Q - 0 1"
},
{
"depth":4,
"nodes":1274206,
"fen":"r3k2r/1b4bq/8/8/8/8/7B/R3K2R w KQkq - 0 1"
},
{
"depth":4,
"nodes":1720476,
"fen":"r3k2r/8/3Q4/8/8/5q2/8/R3K2R b KQkq - 0 1"
},
{
"depth":6,
"nodes":3821001,
"fen":"2K2r2/4P3/8/8/8/8/8/3k4 w - - 0 1"
},
{
"depth":5,
"nodes":1004658,
"fen":"8/8/1P2K3/8/2n5/1q6/8/5k2 b - - 0 1"
},
{
"depth":6,
"nodes":217342,
"fen":"4k3/1P6/8/8/8/8/K7/8 w - - 0 1"
},
{
"depth":6,
"nodes":92683,
"fen":"8/P1k5/K7/8/8/8/8/8 w - - 0 1"
},
{
"depth":6,
"nodes":2217,
"fen":"K1k5/8/P7/8/8/8/8/8 w - - 0 1"
},
{
"depth":7,
"nodes":567584,
"fen":"8/k1P5/8/1K6/8/8/8/8 w - - 0 1"
},
{
"depth":4,
"nodes":23527,
"fen":"8/8/2k5/5q2/5n2/8/5K2/8 b - - 0 1"
}
]
@e3ntity
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e3ntity commented Apr 28, 2021

Some of the FEN notations are messed up. The order in which castling legality is specified must follow "KQkq": https://en.wikipedia.org/wiki/Forsyth–Edwards_Notation (In the german article this is explicitly stated). For example lichess won't recognize this otherwise.

@peterellisjones
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Author

Some of the FEN notations are messed up. The order in which castling legality is specified must follow "KQkq": https://en.wikipedia.org/wiki/Forsyth–Edwards_Notation (In the german article this is explicitly stated). For example lichess won't recognize this otherwise.

Fixed :)

@ajax333221
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8/8/8/2k5/2pP4/8/B7/4K3 b - d3 5 3 the pawn push that created the enpassant should have set the halfmoves to 0, my program was failing to load this position because of this (which I know is a problem in my end as my validator should be more relaxed, but just saying).

@peterellisjones
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Thanks @ajax333221, fixed

@sictransit
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sictransit commented Sep 20, 2022

Thank you! Those helped me find and fix a couple of bugs in my engine.

@shuckc
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shuckc commented Dec 20, 2022

Very useful list, thankyou

@eikopf
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eikopf commented Nov 21, 2023

this is great, thanks so much!

for anyone using this for testing, the following commands will convert this into a comma-delimited list of string literals, so you can stick them in an array or something.

SRC="https://gist.githubusercontent.com/peterellisjones/8c46c28141c162d1d8a0f0badbc9cff9/raw/b11af5a3dd978724ac2d4a531217133b9a3ad9ba/Chess%2520Perft%2520test%2520positions"

curl $SRC | jq ".[] | .fen" | sed "s/\$/,/g"

@DuckyShine004
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Thanks, this was very helpful for debugging my chess engine!

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