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feat: stand-pat on quiescence search

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gotta remember that not capturing is an option too
This commit is contained in:
dogeystamp 2024-12-24 16:46:47 -05:00
parent 54a4cd07ac
commit 0120c95097
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4 changed files with 48 additions and 39 deletions
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11
src/eval.rs
View File

@ -509,16 +509,17 @@ mod tests {
// expected (signed) value gain of exchange
Rook.value(),
),
(
"8/8/4b3/2kq4/2PKP3/8/8/8 w - - 0 1",
"d5",
Queen.value(),
),
("8/8/4b3/2kq4/2PKP3/8/8/8 w - - 0 1", "d5", Queen.value()),
(
"r3k2r/1pq2pbp/6p1/p2Qpb2/1N6/2P3P1/PB2PPBP/R3K2R w KQkq - 0 14",
"e5",
0,
),
(
"r3k2r/1pq2pbp/6p1/p3p3/P5b1/2P3P1/1BN1PPBP/R2QK2R b KQkq - 0 14",
"e2",
0,
),
];
for (fen, dest, expected) in test_cases {

36
src/movegen.rs
View File

@ -1667,25 +1667,23 @@ mod tests {
#[test]
fn test_capture_movegen() {
let test_cases = [(
// fen
"8/3q4/5N2/8/8/8/8/3K4 w - - 0 1",
// expected moves generated
"f6d7",
),
(
"8/8/8/3pP3/2K5/8/8/8 w - d6 0 1",
// holy hell
"e5d6 c4d5",
),
(
"8/2q5/3K4/8/8/8/8/8 w - - 0 1",
"d6c7",
),
(
"2Q5/3r2R1/2B1PN2/8/3K4/8/8/8 w - - 0 1",
"c6d7 e6d7 c8d7 f6d7 g7d7",
),
let test_cases = [
(
// fen
"8/3q4/5N2/8/8/8/8/3K4 w - - 0 1",
// expected moves generated
"f6d7",
),
(
"8/8/8/3pP3/2K5/8/8/8 w - d6 0 1",
// holy hell
"e5d6 c4d5",
),
("8/2q5/3K4/8/8/8/8/8 w - - 0 1", "d6c7"),
(
"2Q5/3r2R1/2B1PN2/8/3K4/8/8/8 w - - 0 1",
"c6d7 e6d7 c8d7 f6d7 g7d7",
),
];
for (fen, expected) in test_cases {

2
src/prelude.rs
View File

@ -23,5 +23,5 @@ pub use crate::search::{
best_line, best_move, EngineState, SearchConfig, SearchEval, TimeLimits, TranspositionTable,
};
pub use crate::{
Board, ColPiece, Color, Piece, BOARD_HEIGHT, BOARD_WIDTH, N_COLORS, N_PIECES, N_SQUARES, Square,
Board, ColPiece, Color, Piece, Square, BOARD_HEIGHT, BOARD_WIDTH, N_COLORS, N_PIECES, N_SQUARES,
};

38
src/search.rs
View File

@ -122,9 +122,8 @@ impl Default for SearchConfig {
fn default() -> Self {
SearchConfig {
alpha_beta_on: true,
// try to make this even to be more conservative and avoid horizon problem
depth: 10,
qdepth: 2,
qdepth: 4,
enable_trans_table: true,
transposition_size: 24,
}
@ -209,13 +208,20 @@ fn minmax(board: &mut Board, state: &mut EngineState, mm: MinmaxState) -> (Vec<M
}
}
// quiescence stand-pat score (only calculated if needed).
// this is where static eval goes.
let mut board_eval: Option<EvalInt> = None;
if mm.quiesce {
board_eval = Some(board.eval() * EvalInt::from(board.turn.sign()));
}
if mm.depth == 0 {
if mm.quiesce || board.recap_sq.is_none() {
// if we're done with quiescence, static eval.
// if there is no capture, skip straight to static eval.
let eval = board.eval() * EvalInt::from(board.turn.sign());
return (Vec::new(), SearchEval::Exact(eval));
if mm.quiesce {
// we hit the limit on quiescence depth
return (Vec::new(), SearchEval::Exact(board_eval.unwrap()));
} else {
// enter quiescence search
return minmax(
board,
state,
@ -261,11 +267,15 @@ fn minmax(board: &mut Board, state: &mut EngineState, mm: MinmaxState) -> (Vec<M
mvs.sort_unstable_by_key(|mv| -mv.0);
let mut abs_best = SearchEval::Exact(EVAL_WORST);
if mm.quiesce {
// stand pat
abs_best = SearchEval::Exact(board_eval.unwrap());
}
let mut best_move: Option<Move> = None;
let mut best_continuation: Vec<Move> = Vec::new();
let n_non_qmoves = mvs.len();
// determine moves that are allowed in quiescence
if mm.quiesce {
// use static exchange evaluation to prune moves
@ -276,7 +286,11 @@ fn minmax(board: &mut Board, state: &mut EngineState, mm: MinmaxState) -> (Vec<M
});
}
if n_non_qmoves == 0 {
if mvs.is_empty() {
if mm.quiesce {
// use stand pat
return (Vec::new(), SearchEval::Exact(board_eval.unwrap()));
}
let is_in_check = board.is_check(board.turn);
if is_in_check {
@ -285,10 +299,6 @@ fn minmax(board: &mut Board, state: &mut EngineState, mm: MinmaxState) -> (Vec<M
// stalemate
return (Vec::new(), SearchEval::Exact(0));
}
} else if mvs.is_empty() {
// pruned all the moves due to quiescence
let eval = board.eval() * EvalInt::from(board.turn.sign());
return (Vec::new(), SearchEval::Exact(eval));
}
for (_priority, mv) in mvs {