feat: Add depth benchmarking tool for engine performance evaluation

Author: miskibin

tools/depth_benchmark.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python
+"""
+Benchmark engine performance at different depths (1-12).
+Shows average time per move for each depth.
+"""
+
+import time
+import sys
+from pathlib import Path
+
+# Add project root to path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from draughts.boards.standard import Board
+from draughts.engine import AlphaBetaEngine
+
+
+# Test positions - mix of opening, midgame, and endgame
+TEST_POSITIONS = [
+    None,  # Starting position
+    '[FEN "W:W31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50:B1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20"]',
+    '[FEN "W:W27,28,32,33,37,38,42,43,47,48:B3,4,8,9,13,14,18,19,23,24"]',
+    '[FEN "B:W24,28,29,30,33,34,38,39,44,45,49,50:B1,2,6,7,8,12,13,17,18,22,23,27"]',
+    '[FEN "W:WK10,K20:BK30,K40"]',  # King endgame
+    '[FEN "W:W45,50:B5,10"]',  # Simple endgame
+]
+
+MOVES_PER_POSITION = 3  # Number of moves to make per position
+
+
+def benchmark_depth(depth: int) -> dict:
+    """Benchmark engine at given depth, return stats."""
+    engine = AlphaBetaEngine(depth=depth)
+    
+    total_time = 0.0
+    total_moves = 0
+    total_nodes = 0
+    
+    for fen in TEST_POSITIONS:
+        if fen:
+            board = Board.from_fen(fen)
+        else:
+            board = Board()
+        
+        for _ in range(MOVES_PER_POSITION):
+            if not list(board.legal_moves):
+                break
+            
+            engine.nodes = 0
+            start = time.perf_counter()
+            move = engine.get_best_move(board)
+            elapsed = time.perf_counter() - start
+            
+            total_time += elapsed
+            total_moves += 1
+            total_nodes += engine.nodes
+            
+            board.push(move)
+    
+    return {
+        "depth": depth,
+        "total_moves": total_moves,
+        "avg_time_ms": (total_time / total_moves * 1000) if total_moves > 0 else 0,
+        "avg_nodes": total_nodes // total_moves if total_moves > 0 else 0,
+        "total_time": total_time,
+    }
+
+
+def main():
+    print("=" * 70)
+    print("Engine Depth Benchmark")
+    print("=" * 70)
+    print(f"Testing {len(TEST_POSITIONS)} positions, {MOVES_PER_POSITION} moves each")
+    print()
+    print(f"{'Depth':>6} | {'Avg Time':>12} | {'Avg Nodes':>12} | {'Total Time':>12}")
+    print("-" * 70)
+    
+    results = []
+    
+    for depth in range(1, 13):
+        result = benchmark_depth(depth)
+        results.append(result)
+        
+        avg_time = result["avg_time_ms"]
+        if avg_time < 1000:
+            time_str = f"{avg_time:.2f} ms"
+        else:
+            time_str = f"{avg_time/1000:.2f} s"
+        
+        total_time = result["total_time"]
+        if total_time < 60:
+            total_str = f"{total_time:.2f} s"
+        else:
+            total_str = f"{total_time/60:.1f} min"
+        
+        print(f"{depth:>6} | {time_str:>12} | {result['avg_nodes']:>12,} | {total_str:>12}")
+        
+        # Stop if taking too long (> 30s per move on average)
+        if avg_time > 30000:
+            print(f"\nStopping - depth {depth} takes > 30s per move")
+            break
+    
+    print("=" * 70)
+
+
+if __name__ == "__main__":
+    main()