Added a form of Late Move Pruning (Move Count Pruning)

------------------------------------------------------------------------------- LateMovePruning10 @ 30.0+0.3 with 128MB Hash Base Alpha Beta Games Test Elo Base Elo Status QuietHistory2 0.05 0.10 14000 2727.24 2716.08 PASSED MATCHUPS FOR CANDIDATE Opponent Wins Draws Losses Games Score ELO + - Floyd0.9 460 118 172 750 69.20% 2730.62 27.82 26.20 Laser1.0 279 214 307 800 48.25% 2714.83 24.07 24.19 Sloppy0.2.2 483 162 155 800 70.50% 2768.35 27.30 25.65 WyldChess1.4 438 174 138 750 70.00% 2757.19 28.07 26.36 DiscoCheck4.03 207 208 335 750 41.47% 2652.12 24.97 25.60 RedQueen1.1.98 262 194 294 750 47.87% 2657.17 24.85 25.01 Ethereal8.15 365 287 98 750 67.80% 2743.35 27.41 25.95 Tucano3.0 430 166 104 700 73.29% 2794.31 30.34 28.05 MATCHUPS FOR BASE Opponent Wins Draws Losses Games Score ELO + - Floyd0.9 434 121 195 750 65.93% 2704.71 26.93 25.66 Laser1.0 267 212 321 800 46.62% 2703.51 24.06 24.28 Sloppy0.2.2 464 174 162 800 68.88% 2754.98 26.81 25.33 WyldChess1.4 645 289 216 1150 68.65% 2746.18 22.19 21.18 DiscoCheck4.03 228 197 325 750 43.53% 2666.81 24.89 25.36 RedQueen1.1.98 466 328 606 1400 45.00% 2637.14 18.21 18.41 Ethereal8.15 365 311 124 800 65.06% 2722.02 25.86 24.75 Tucano3.0 909 377 214 1500 73.17% 2793.26 20.40 19.35 ------------------------------------------------------------------------------- LateMovePruning10 @ 5.0+0.05 with 128MB Hash Base Alpha Beta Games Test Elo Base Elo Status QuietHistory2 0.05 0.10 18000 2738.19 2729.73 PASSED MATCHUPS FOR CANDIDATE Opponent Wins Draws Losses Games Score ELO + - Floyd0.9 801 111 188 1100 77.86% 2808.49 25.80 23.82 Laser1.0 399 254 397 1050 50.10% 2727.66 21.04 21.04 Sloppy0.2.2 629 179 242 1050 68.43% 2751.38 23.20 22.11 WyldChess1.4 697 197 206 1100 72.32% 2776.82 23.68 22.32 DiscoCheck4.03 287 245 518 1050 39.00% 2634.29 21.28 21.87 RedQueen1.1.98 416 224 360 1000 52.80% 2691.48 21.67 21.52 Ethereal8.15 491 359 200 1050 63.86% 2712.87 22.29 21.52 Tucano3.0 635 214 151 1000 74.20% 2802.51 25.53 23.83 MATCHUPS FOR BASE Opponent Wins Draws Losses Games Score ELO + - Floyd0.9 785 125 190 1100 77.05% 2800.35 25.42 23.55 Laser1.0 387 241 472 1100 46.14% 2700.10 20.52 20.71 Sloppy0.2.2 615 186 249 1050 67.43% 2743.40 22.97 21.96 WyldChess1.4 639 206 205 1050 70.67% 2762.74 23.77 22.49 DiscoCheck4.03 288 225 537 1050 38.14% 2628.01 21.34 21.99 RedQueen1.1.98 762 371 667 1800 52.64% 2690.35 16.12 16.05 Ethereal8.15 494 390 216 1100 62.64% 2703.75 21.58 20.92 Tucano3.0 881 261 208 1350 74.93% 2809.16 22.09 20.77
AndyGrant · Jul 13, 2017 · 8cd0115 · 8cd0115
1 parent 0374e40
commit 8cd0115
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Showing 5 changed files with 23 additions and 7 deletions.
diff --git a/dist/Ethereal8.20.zip b/dist/Ethereal8.20.zip
diff --git a/dist/Ethereal8.22.zip b/dist/Ethereal8.22.zip
diff --git a/src/search.c b/src/search.c
@@ -251,10 +251,11 @@ int rootSearch(PVariation * pv, Board * board, MoveList * moveList, int alpha,
 int alphaBetaSearch(PVariation * pv, Board * board, int alpha, int beta, 
                                    int depth, int height, int nodeType){
 
-    int i, value, inCheck, isQuiet, hist, R;
+    int i, value, inCheck, isQuiet, R;
     int min, max, entryValue, entryType, oldAlpha = alpha;
     int quiets = 0, played = 0, avoidedQS = 0, tableIsTactical = 0; 
     int best = -MATE, eval = -MATE, optimal = -MATE;
+    int hist = 0; // Fix bogus GCC warning
 
     uint16_t currentMove, killer1, killer2, quietsTried[MAX_MOVES];
     uint16_t tableMove = NONE_MOVE, bestMove = NONE_MOVE;
@@ -405,9 +406,23 @@ int alphaBetaSearch(PVariation * pv, Board * board, int alpha, int beta,
 
     while ((currentMove = selectNextMove(&movePicker, board)) != NONE_MOVE){
 
-        // Save this to the quiets list if it is quiet
-        isQuiet = !moveIsTactical(board, currentMove);
-        if (isQuiet) quietsTried[quiets++] = currentMove;
+        // If this move is quiet we will save it to a list of attemped
+        // quiets, and we will need a history score for pruning decisions
+        if ((isQuiet = !moveIsTactical(board, currentMove))){
+            quietsTried[quiets++] = currentMove;
+            hist = getHistoryScore(History, currentMove, board->turn, 128);
+        }
+
+        // Late Move Pruning
+        if (USE_LATE_MOVE_PRUNING
+            && nodeType != PVNODE
+            && played >= 1
+            && !inCheck
+            && isQuiet
+            && depth < 6
+            && quiets > LateMovePruningCounts[depth]
+            && hist < 32)
+            continue;
 
         // Use futility pruning
         if (USE_FUTILITY_PRUNING
@@ -436,8 +451,6 @@ int alphaBetaSearch(PVariation * pv, Board * board, int alpha, int beta,
             && !inCheck
             && isQuiet
             && isNotInCheck(board, board->turn)){
-
-            hist = getHistoryScore(History, currentMove, !board->turn, 128);
 
             R = 2;
             R += (played - 4) / 8;

diff --git a/src/search.h b/src/search.h
@@ -44,11 +44,14 @@ int moveIsTactical(Board * board, uint16_t move);
 
 int moveWasTactical(Undo * undo, uint16_t move);
 
+static const int LateMovePruningCounts[6] = {0, 6, 11, 15, 20, 25}; 
+
 #define USE_STATIC_NULL_PRUNING             (1)
 #define USE_FUTILITY_PRUNING                (1)
 #define USE_NULL_MOVE_PRUNING               (1)
 #define USE_LATE_MOVE_REDUCTIONS            (1)
 #define USE_INTERNAL_ITERATIVE_DEEPENING    (1)
 #define USE_TRANSPOSITION_TABLE             (1)
+#define USE_LATE_MOVE_PRUNING               (1)
 
 #endif
diff --git a/src/uci.c b/src/uci.c
@@ -82,7 +82,7 @@ int main(){
            http://wbec-ridderkerk.nl/html/UCIProtocol.html */
 
         if (stringEquals(str, "uci")){
-            printf("id name Ethereal 8.21\n");
+            printf("id name Ethereal 8.22\n");
             printf("id author Andrew Grant\n");
             printf("option name Hash type spin default 16 min 1 max 2048\n");
             printf("uciok\n");