Move hindsight reductions above cutoffs

daniel-monroe · vondele · commit 5297ba0a1a1a · 2025-12-01T17:35:34.000+01:00
Passed STC LLR: 2.93 (-2.94,2.94) <0.00,2.00> Total: 52640 W: 13701 L: 13361 D: 25578 Ptnml(0-2): 168, 6143, 13356, 6487, 166 https://tests.stockfishchess.org/tests/view/6918dc407ca8781852332339 Passed LTC LLR: 2.95 (-2.94,2.94) <0.50,2.50> Total: 207690 W: 53187 L: 52520 D: 101983 Ptnml(0-2): 93, 22515, 57994, 23118, 125 https://tests.stockfishchess.org/tests/view/6919dd307ca87818523324c7 closes #6448 Bench: 2912398
diff --git a/src/search.cpp b/src/search.cpp
@@ -702,6 +702,56 @@ Value Search::Worker::search(
     // At this point, if excluded, skip straight to step 6, static eval. However,
     // to save indentation, we list the condition in all code between here and there.
 
+    // Step 6. Static evaluation of the position
+    Value      unadjustedStaticEval = VALUE_NONE;
+    const auto correctionValue      = correction_value(*this, pos, ss);
+    if (ss->inCheck)
+    {
+        // Skip early pruning when in check
+        ss->staticEval = eval = (ss - 2)->staticEval;
+        improving             = false;
+    }
+    else if (excludedMove)
+        unadjustedStaticEval = eval = ss->staticEval;
+    else if (ss->ttHit)
+    {
+        // Never assume anything about values stored in TT
+        unadjustedStaticEval = ttData.eval;
+        if (!is_valid(unadjustedStaticEval))
+            unadjustedStaticEval = evaluate(pos);
+
+        ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
+
+        // ttValue can be used as a better position evaluation
+        if (is_valid(ttData.value)
+            && (ttData.bound & (ttData.value > eval ? BOUND_LOWER : BOUND_UPPER)))
+            eval = ttData.value;
+    }
+    else
+    {
+        unadjustedStaticEval = evaluate(pos);
+        ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
+
+        // Static evaluation is saved as it was before adjustment by correction history
+        ttWriter.write(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_UNSEARCHED, Move::none(),
+                       unadjustedStaticEval, tt.generation());
+    }
+
+    // Set up the improving flag, which is true if current static evaluation is
+    // bigger than the previous static evaluation at our turn (if we were in
+    // check at our previous move we go back until we weren't in check) and is
+    // false otherwise. The improving flag is used in various pruning heuristics.
+    // Similarly, opponentWorsening is true if our static evaluation is better
+    // for us than at the last ply.
+    improving         = ss->staticEval > (ss - 2)->staticEval;
+    opponentWorsening = ss->staticEval > -(ss - 1)->staticEval;
+
+    // Hindsight adjustment of reductions based on static evaluation difference.
+    if (priorReduction >= 3 && !opponentWorsening)
+        depth++;
+    if (priorReduction >= 2 && depth >= 2 && ss->staticEval + (ss - 1)->staticEval > 173)
+        depth--;
+
     // At non-PV nodes we check for an early TT cutoff
     if (!PvNode && !excludedMove && ttData.depth > depth - (ttData.value <= beta)
         && is_valid(ttData.value)  // Can happen when !ttHit or when access race in probe()
@@ -799,41 +849,8 @@ Value Search::Worker::search(
         }
     }
 
-    // Step 6. Static evaluation of the position
-    Value      unadjustedStaticEval = VALUE_NONE;
-    const auto correctionValue      = correction_value(*this, pos, ss);
     if (ss->inCheck)
-    {
-        // Skip early pruning when in check
-        ss->staticEval = eval = (ss - 2)->staticEval;
-        improving             = false;
         goto moves_loop;
-    }
-    else if (excludedMove)
-        unadjustedStaticEval = eval = ss->staticEval;
-    else if (ss->ttHit)
-    {
-        // Never assume anything about values stored in TT
-        unadjustedStaticEval = ttData.eval;
-        if (!is_valid(unadjustedStaticEval))
-            unadjustedStaticEval = evaluate(pos);
-
-        ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
-
-        // ttValue can be used as a better position evaluation
-        if (is_valid(ttData.value)
-            && (ttData.bound & (ttData.value > eval ? BOUND_LOWER : BOUND_UPPER)))
-            eval = ttData.value;
-    }
-    else
-    {
-        unadjustedStaticEval = evaluate(pos);
-        ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
-
-        // Static evaluation is saved as it was before adjustment by correction history
-        ttWriter.write(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_UNSEARCHED, Move::none(),
-                       unadjustedStaticEval, tt.generation());
-    }
 
     // Use static evaluation difference to improve quiet move ordering
     if (((ss - 1)->currentMove).is_ok() && !(ss - 1)->inCheck && !priorCapture)
@@ -845,21 +862,6 @@ Value Search::Worker::search(
             pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq] << evalDiff * 13;
     }
 
-    // Set up the improving flag, which is true if current static evaluation is
-    // bigger than the previous static evaluation at our turn (if we were in
-    // check at our previous move we go back until we weren't in check) and is
-    // false otherwise. The improving flag is used in various pruning heuristics.
-    // Similarly, opponentWorsening is true if our static evaluation is better
-    // for us than at the last ply.
-    improving         = ss->staticEval > (ss - 2)->staticEval;
-    opponentWorsening = ss->staticEval > -(ss - 1)->staticEval;
-
-    // Hindsight adjustment of reductions based on static evaluation difference.
-    if (priorReduction >= 3 && !opponentWorsening)
-        depth++;
-
-    if (priorReduction >= 2 && depth >= 2 && ss->staticEval + (ss - 1)->staticEval > 169)
-        depth--;
 
     // Step 7. Razoring
     // If eval is really low, skip search entirely and return the qsearch value.
