From 6b7e05f0c5287179de25a0722f9eea0f87f64648 Mon Sep 17 00:00:00 2001
From: Shawn Xu <xu107288696@gmail.com>
Date: Fri, 9 May 2025 15:34:36 -0700
Subject: [PATCH] Simplify PCM TTMove Bonus

Passed Non-regression STC:
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 114048 W: 29597 L: 29459 D: 54992
Ptnml(0-2): 315, 13619, 29045, 13703, 342
https://tests.stockfishchess.org/tests/view/681e83533629b02d74b17701

Passed Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 61014 W: 15582 L: 15405 D: 30027
Ptnml(0-2): 25, 6485, 17307, 6668, 22
https://tests.stockfishchess.org/tests/view/68226b523629b02d74b17b89

closes https://github.com/official-stockfish/Stockfish/pull/6061

bench 2016566
---
 src/search.cpp | 14 ++++++--------
 src/search.h   |  1 -
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index 6827f5127..4fca84f95 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -921,7 +921,6 @@ Value Search::Worker::search(
             do_move(pos, move, st);
 
             ss->currentMove = move;
-            ss->isTTMove    = (move == ttData.move);
             ss->continuationHistory =
               &this->continuationHistory[ss->inCheck][true][movedPiece][move.to_sq()];
             ss->continuationCorrectionHistory =
@@ -1172,7 +1171,6 @@ moves_loop:  // When in check, search starts here
 
         // Update the current move (this must be done after singular extension search)
         ss->currentMove = move;
-        ss->isTTMove    = (move == ttData.move);
         ss->continuationHistory =
           &thisThread->continuationHistory[ss->inCheck][capture][movedPiece][move.to_sq()];
         ss->continuationCorrectionHistory =
@@ -1203,7 +1201,7 @@ moves_loop:  // When in check, search starts here
             r += 1036 + allNode * 848;
 
         // For first picked move (ttMove) reduce reduction
-        else if (ss->isTTMove)
+        else if (move == ttData.move)
             r -= 2006;
 
         if (capture)
@@ -1285,7 +1283,7 @@ moves_loop:  // When in check, search starts here
             (ss + 1)->pv[0] = Move::none();
 
             // Extend move from transposition table if we are about to dive into qsearch.
-            if (ss->isTTMove && thisThread->rootDepth > 8)
+            if (move == ttData.move && thisThread->rootDepth > 8)
                 newDepth = std::max(newDepth, 1);
 
             value = -search<PV>(pos, ss + 1, -beta, -alpha, newDepth, false);
@@ -1423,7 +1421,7 @@ moves_loop:  // When in check, search starts here
                          ttData.move, moveCount);
         if (!PvNode)
         {
-            int bonus = ss->isTTMove ? 800 : -879;
+            int bonus = bestMove == ttData.move ? 800 : -879;
             ttMoveHistory << bonus;
         }
     }
@@ -1431,11 +1429,11 @@ moves_loop:  // When in check, search starts here
     // Bonus for prior quiet countermove that caused the fail low
     else if (!priorCapture && prevSq != SQ_NONE)
     {
-        int bonusScale = std::min(-(ss - 1)->statScore / 113, 293);
-        bonusScale += std::min(73 * depth - 347, 184);
+        int bonusScale = -324;
+        bonusScale += std::min(-(ss - 1)->statScore / 103, 323);
+        bonusScale += std::min(73 * depth, 531);
         bonusScale += 33 * !allNode;
         bonusScale += 174 * ((ss - 1)->moveCount > 8);
-        bonusScale += 86 * (ss - 1)->isTTMove;
         bonusScale += 90 * (ss->cutoffCnt <= 3);
         bonusScale += 144 * (!ss->inCheck && bestValue <= ss->staticEval - 104);
         bonusScale += 128 * (!(ss - 1)->inCheck && bestValue <= -(ss - 1)->staticEval - 82);
diff --git a/src/search.h b/src/search.h
index 6ab98f7c4..0c041c826 100644
--- a/src/search.h
+++ b/src/search.h
@@ -75,7 +75,6 @@ struct Stack {
     bool                        ttHit;
     int                         cutoffCnt;
     int                         reduction;
-    bool                        isTTMove;
     bool                        isPvNode;
 };