prefetch: 实现不需要模拟走子的预取 (目前只实现了吃子) 并启用预取

自对弈时长由 22s 缩短到 20.5s。

include/config.h

@@ -95,7 +95,7 @@
 //#define TRANSPOSITION_TABLE_DEBUG
 #endif
 
-//#define PREFETCH_SUPPORT
+#define PREFETCH_SUPPORT
 
 //#define USE_STD_STACK
 

src/ai/search.cpp

@@ -862,18 +862,14 @@ value_t AIAlgorithm::search(depth_t depth, value_t alpha, value_t beta, Node *no
 #endif // CLEAR_PRUNED_FLAG_BEFORE_SEARCH
 
     int nchild = node->childrenSize;
-    for (int i = 0; i < nchild; i++) {
+
 #ifdef PREFETCH_SUPPORT
-        if (i + 1 < nchild)
-        {
-            stashPosition();
-            doMove(node->children[i + 1]->move);
-            hash_t nextHash = st->getHash();
-            TT::prefetchHash(nextHash);
-            undoMove();
+    for (int i = 0; i < nchild; i++) {
+        TT::prefetchHash(st->getNextMainHash(node->children[i]->move));
     }
 #endif // PREFETCH_SUPPORT
 
+    for (int i = 0; i < nchild; i++) {
         // 棋局入栈保存，以便后续撤销着法
         stashPosition();
 

src/game/position.cpp

@@ -1171,3 +1171,32 @@ hash_t StateInfo::updateHashMisc()
 
     return position->hash;
 }
+
+hash_t StateInfo::getNextMainHash(move_t m)
+{
+    hash_t nextMainHash = position->hash << 8 >> 8;
+    square_t sq = SQ_0;
+
+    if (m < 0) {
+        sq = static_cast<square_t>(-m);
+        int pieceType = Player::toId(position->board.locationToPlayer(sq));
+        nextMainHash ^= zobrist[sq][pieceType];
+
+        if (rule.hasForbiddenLocations && position->phase == PHASE_PLACING) {
+            nextMainHash ^= zobrist[sq][PIECETYPE_FORBIDDEN];
+        }
+    }
+
+#if 0
+    if (m & 0x1f00) {
+        if (choose(static_cast<square_t>(m >> 8))) {
+            return place(static_cast<square_t>(m & 0x00ff));
+        }
+    } else {
+        return place(static_cast<square_t>(m & 0x00ff));
+    }
+#endif
+
+    return nextMainHash;
+}
+

src/game/position.h

@@ -264,6 +264,7 @@ public:
     hash_t revertHash(square_t square);
     hash_t updateHash(square_t square);
     hash_t updateHashMisc();
+    hash_t StateInfo::getNextMainHash(move_t m);
 
 #ifdef MCTS_AI
     // MCTS 相关