remove vcf search

Rapfi/search/ab/search.cpp

@@ -638,12 +638,6 @@ Value search(Board &board, SearchStack *ss, Value alpha, Value beta, Depth depth
     uint16_t oppo5 = board.p4Count(oppo, A_FIVE);           // opponent five
     uint16_t oppo4 = oppo5 + board.p4Count(oppo, B_FLEX4);  // opponent straight four and five
 
-    // Dive into vcf search when the depth reaches zero (~17 elo)
-    if (depth <= 0.0f) {
-        return oppo5 ? vcfdefend<Rule, NT>(board, ss, alpha, beta)
-                     : vcfsearch<Rule, NT>(board, ss, alpha, beta);
-    }
-
     int            moveCount = 0, nonMatedCount = 0;
     Value          bestValue = -VALUE_INFINITE, maxValue = VALUE_INFINITE, value;
     Pos            bestMove = Pos::NONE;
@@ -794,11 +788,7 @@ Value search(Board &board, SearchStack *ss, Value alpha, Value beta, Depth depth
     Value eval        = VALUE_NONE;
     int   improvement = 0;  // Static eval change in the last two ply
 
-    // Reset killer of grand-children
-    (ss + 2)->killers[0] = Pos::NONE;
-    (ss + 2)->killers[1] = Pos::NONE;
-
-    if (oppo4) {
+    if (oppo4 && depth > 0.0f) {
         // Use static evaluation from previous ply if opponent makes a four/five attack
         ss->staticEval = -(ss - 1)->staticEval;
 
@@ -833,8 +823,16 @@ Value search(Board &board, SearchStack *ss, Value alpha, Value beta, Depth depth
         }
 
         improvement = ss->staticEval - (ss - 2)->staticEval;
+
+        // Return static eval when the depth reaches zero
+        if (depth <= 0.0f)
+            return ss->staticEval;
     }
 
+    // Reset killer of grand-children
+    (ss + 2)->killers[0] = Pos::NONE;
+    (ss + 2)->killers[1] = Pos::NONE;
+
     // Step 7. Razoring with VCF (~68 elo)
     if (!PvNode
         && (alpha < VALUE_MATE_IN_MAX_PLY || !ttHit)  // We are not searching for a short win