[3/6] Add MVV-LVA capture ordering and killer moves heuristic #35
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Enhances quiescence search with better handling of special positions: **Draw Detection:** - Check fifty-move rule and insufficient material - Detect repetitions when making moves (return 0 for draws) **Check Handling:** - When in check, search ALL legal moves (evasions), not just captures - Can't use stand-pat for pruning when in check (position is unstable) - Separate best_score tracking for in-check vs normal positions **Tactical Move Detection:** - Add `is_tactical_move()` helper function - Tactical moves: captures, promotions, and checks - Previously included quiet pawn pushes (is_zeroing), now more precise **Move Ordering:** - Update `organize_moves_quiescence()` to use is_tactical_move - Sort tactical moves by MVV-LVA Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Improves move ordering for better pruning: **MVV-LVA (Most Valuable Victim - Least Valuable Attacker):** - Sort captures by MVV-LVA score in `organize_moves()` - Best captures (e.g., pawn takes queen) searched first - Increases beta cutoff rate for better pruning **Killer Moves Heuristic:** - Track quiet moves that cause beta cutoffs (2 per ply) - Add `killers` parameter to `organize_moves()` and `negamax()` - Killer moves searched after captures, before other quiet moves - Killers stored in a table indexed by ply depth **Move Ordering Priority:** 1. Captures (sorted by MVV-LVA) 2. Killer moves (quiet moves that caused cutoffs at this ply) 3. Other quiet moves (shuffled for variety) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Details
MVV-LVA Capture Ordering
Captures are now sorted by MVV-LVA score, putting the best captures first:
Killer Moves Heuristic
Quiet moves that caused beta cutoffs are remembered:
Move Ordering Priority
Test plan
🤖 Generated with Claude Code