68 lines
2.2 KiB
Rust
68 lines
2.2 KiB
Rust
use crate::board::{Bitboard, Square};
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use crate::movegen::naive::{bishop::bishop_moves, rook::rook_moves};
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use crate::movegen::Magic;
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use super::mask::{generate_bishop_mask, generate_rook_mask};
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type MagicGenerationType = (Vec<Magic>, Vec<Bitboard>);
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#[allow(unused)] // FIXME: remove when used
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pub fn generate_bishop_magics(rng: &mut dyn random::Source) -> MagicGenerationType {
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generate_magics(rng, generate_bishop_mask, bishop_moves)
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}
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#[allow(unused)] // FIXME: remove when used
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pub fn generate_rook_magics(rng: &mut dyn random::Source) -> MagicGenerationType {
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generate_magics(rng, generate_rook_mask, rook_moves)
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}
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fn generate_magics(
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rng: &mut dyn random::Source,
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mask_fn: impl Fn(Square) -> Bitboard,
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moves_fn: impl Fn(Square, Bitboard) -> Bitboard,
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) -> MagicGenerationType {
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let mut magics = Vec::new();
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let mut boards = Vec::new();
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for square in Square::iter() {
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let mask = mask_fn(square);
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let mut candidate: Magic;
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let occupancy_to_moves: Vec<_> = mask
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.iter_power_set()
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.map(|occupancy| (occupancy, moves_fn(square, occupancy)))
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.collect();
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'candidate_search: loop {
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candidate = Magic {
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magic: magic_candidate(rng),
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offset: 0,
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mask,
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shift: (64 - mask.count()) as u8,
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};
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let mut candidate_moves = vec![Bitboard::EMPTY; occupancy_to_moves.len()];
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for (occupancy, moves) in occupancy_to_moves.iter().cloned() {
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let index = candidate.get_index(occupancy);
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// Non-constructive collision, try with another candidate
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if candidate_moves[index] != Bitboard::EMPTY && candidate_moves[index] != moves {
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continue 'candidate_search;
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}
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candidate_moves[index] = moves;
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}
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// We have filled all candidate boards, record the correct offset and add the moves
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candidate.offset = boards.len();
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boards.append(&mut candidate_moves);
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magics.push(candidate);
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break;
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}
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}
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(magics, boards)
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}
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fn magic_candidate(rng: &mut dyn random::Source) -> u64 {
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rng.read_u64() & rng.read_u64() & rng.read_u64()
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}
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