Refactor pure static eval code

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d43a875f68168f4c58f64907daba4c88daf4df7d..03a8bfcd0885fc0d6d92e6079ffbf816ef789733 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -556,7 +556,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
-    Value bestValue, value, ttValue, eval, maxValue;
+    Value bestValue, value, ttValue, eval, maxValue, pureStaticEval;
     bool ttHit, inCheck, givesCheck, improving;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
     Piece movedPiece;
@@ -705,15 +705,16 @@ namespace {
     // Step 6. Static evaluation of the position
     if (inCheck)
     {
-        ss->staticEval = eval = VALUE_NONE;
+        ss->staticEval = eval = pureStaticEval = VALUE_NONE;
         improving = false;
         goto moves_loop;  // Skip early pruning when in check
     }
     else if (ttHit)
     {
         // Never assume anything on values stored in TT
-        if ((ss->staticEval = eval = tte->eval()) == VALUE_NONE)
-            eval = ss->staticEval = evaluate(pos) - 10 * ((ss-1)->statScore > 0);
+        ss->staticEval = eval = pureStaticEval = tte->eval();
+        if (eval == VALUE_NONE)
+            ss->staticEval = eval = pureStaticEval = evaluate(pos);
 
         // Can ttValue be used as a better position evaluation?
         if (    ttValue != VALUE_NONE
@@ -722,12 +723,19 @@ namespace {
     }
     else
     {
-        ss->staticEval = eval =
-        (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) - 10 * ((ss-1)->statScore > 0)
-                                         : -(ss-1)->staticEval + 2 * Eval::Tempo;
+        if ((ss-1)->currentMove != MOVE_NULL)
+        {
+            int p = (ss-1)->statScore;
+            int bonus = p > 0 ? (-p - 2500) / 512 :
+                        p < 0 ? (-p + 2500) / 512 : 0;
+
+            pureStaticEval = evaluate(pos);
+            ss->staticEval = eval = pureStaticEval + bonus;
+        }
+        else
+            ss->staticEval = eval = pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo;
 
-        tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
-                  ss->staticEval);
+        tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval);
     }
 
     // Step 7. Razoring (~2 Elo)
@@ -1177,7 +1185,7 @@ moves_loop: // When in check, search starts from here
         tte->save(posKey, value_to_tt(bestValue, ss->ply),
                   bestValue >= beta ? BOUND_LOWER :
                   PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
-                  depth, bestMove, ss->staticEval);
+                  depth, bestMove, pureStaticEval);
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);