60 lines
No EOL
1.9 KiB
Python
60 lines
No EOL
1.9 KiB
Python
#!/usr/bin/env python3
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def generate_knight_attacks():
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"""
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Generates a list of 64 u64 bitboards, where each bitboard represents
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the squares a knight can attack from a given source square.
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Uses Little-Endian File-Rank (LEFR) mapping: A1=0, H1=7, A2=8, ..., H8=63.
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"""
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all_attacks = []
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# All 8 possible knight move offsets (delta_file, delta_rank)
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knight_moves = [
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(1, 2), (1, -2), (-1, 2), (-1, -2),
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(2, 1), (2, -1), (-2, 1), (-2, -1)
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]
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for sq in range(64):
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attacks_bb = 0
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# Calculate rank and file for the source square
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rank = sq // 8
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file = sq % 8
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for df, dr in knight_moves:
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target_rank = rank + dr
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target_file = file + df
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# Check if the target square is on the board
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if 0 <= target_rank <= 7 and 0 <= target_file <= 7:
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# Convert target rank and file back to a square index
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target_sq = target_rank * 8 + target_file
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# Set the corresponding bit in the bitboard
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attacks_bb |= (1 << target_sq)
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all_attacks.append(attacks_bb)
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return all_attacks
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def print_rust_array(attacks):
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"""
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Prints the list of attack bitboards as a Rust array.
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"""
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print("pub const KNIGHT_ATTACKS: [u64; 64] = [")
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for i, attacks_bb in enumerate(attacks):
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# Format as 64-bit zero-padded binary string
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raw_binary_string = f"{attacks_bb:064b}"
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# Insert underscores every 8 bits for readability
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chunks = [raw_binary_string[i:i+8] for i in range(0, 64, 8)]
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binary_string = f"0b{'_'.join(chunks)}"
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# Correctly index the string 'ABCDEFGH'
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print(f" {binary_string}, // Square {i} ({'ABCDEFGH'[i%8]}{i//8 + 1})")
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print("];")
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if __name__ == "__main__":
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attacks = generate_knight_attacks()
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print_rust_array(attacks) |