[2/6] Fix transposition table with proper bounds #32
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Implements correct transposition table behavior with bound types: **Transposition Table Changes:** - Add `Bound` enum: EXACT, LOWER_BOUND, UPPER_BOUND - Use Zobrist hash as cache key (fast integer vs slow FEN string) - Store bound type and depth with each cache entry - Only use cached scores when depth is sufficient - Properly handle bound types in lookups: - EXACT: use score directly - LOWER_BOUND: use if score >= beta (fail high) - UPPER_BOUND: use if score <= alpha (fail low) **Null Move Pruning Fix:** - Added missing `null_move` parameter check (was always trying null move) **Parallel Engine Updates:** - Update lazy_smp, l1p, l2p to use new zobrist hash cache key - Add context managers for Pool/Manager (proper resource cleanup) - Fix score negation in l1p (opponent perspective -> our perspective) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Boundenum (EXACT, LOWER_BOUND, UPPER_BOUND) for correct TT behaviornull_moveparameter check)Details
The transposition table now correctly stores and uses bound information:
This prevents incorrect cutoffs and score usage that can cause search instability.
Parallel Engine Updates
All parallel engines (lazy_smp, l1p, l2p) updated to:
Test plan
🤖 Generated with Claude Code