Tweak usage of correction history

Instead of using linear formula use quadratic one. Maximum impact of correction history is doubled this way, it breaks even with previous formula on half of maximum value.
williamgateszhao · Jan 11, 2024 · deb7afe · deb7afe
1 parent 366f8f9
commit deb7afe
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Showing 3 changed files with 25 additions and 10 deletions.
diff --git a/src/movepick.cpp b/src/movepick.cpp
@@ -31,19 +31,26 @@ namespace Stockfish {
 namespace {
 
 enum Stages {
+    // generate main search moves
     MAIN_TT,
     CAPTURE_INIT,
     GOOD_CAPTURE,
     REFUTATION,
     QUIET_INIT,
     QUIET,
     BAD_CAPTURE,
+
+    // generate evasion moves
     EVASION_TT,
     EVASION_INIT,
     EVASION,
+
+    // generate probcut moves
     PROBCUT_TT,
     PROBCUT_INIT,
     PROBCUT,
+
+    // generate qsearch moves
     QSEARCH_TT,
     QCAPTURE_INIT,
     QCAPTURE,

diff --git a/src/nnue/features/half_ka_v2_hm.h b/src/nnue/features/half_ka_v2_hm.h
@@ -39,6 +39,7 @@ namespace Stockfish::Eval::NNUE::Features {
 // position of pieces. Position mirrored such that king is always on d..e files.
 class HalfKAv2_hm {
 
+    // clang-format off
     // Unique number for each piece type on each square
     enum {
         PS_NONE     = 0,
@@ -48,14 +49,11 @@ class HalfKAv2_hm {
         PS_B_CANNON = 3 * SQUARE_NB,
         PS_W_KNIGHT = 4 * SQUARE_NB,
         PS_B_KNIGHT = 5 * SQUARE_NB,
-        PS_AB_W_KP =
-          6
-          * SQUARE_NB,  // White King and Pawn are merged into one plane, also used for Advisor and Bishop
-        PS_B_KP = 7 * SQUARE_NB,  // Black King and Pawn are merged into one plane
-        PS_NB   = 8 * SQUARE_NB
+        PS_AB_W_KP  = 6 * SQUARE_NB,  // White King and Pawn are merged into one plane, also used for Advisor and Bishop
+        PS_B_KP     = 7 * SQUARE_NB,  // Black King and Pawn are merged into one plane
+        PS_NB       = 8 * SQUARE_NB
     };
 
-    // clang-format off
     static constexpr IndexType PieceSquareIndex[COLOR_NB][PIECE_NB] = {
       // Convention: W - us, B - them
       // Viewed from other side, W and B are reversed

diff --git a/src/search.cpp b/src/search.cpp
@@ -623,7 +623,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
 
         Value newEval =
           ss->staticEval
-          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+              * std::abs(thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+              / 16384;
 
         ss->staticEval = eval = to_static_eval(newEval);
 
@@ -637,7 +639,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
 
         Value newEval =
           ss->staticEval
-          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+              * std::abs(thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+              / 16384;
 
         ss->staticEval = eval = to_static_eval(newEval);
 
@@ -1366,7 +1370,10 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
 
             Value newEval =
               ss->staticEval
-              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+                  * std::abs(
+                    thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+                  / 16384;
 
             ss->staticEval = bestValue = to_static_eval(newEval);
 
@@ -1383,7 +1390,10 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
 
             Value newEval =
               ss->staticEval
-              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+                  * std::abs(
+                    thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+                  / 16384;
 
             ss->staticEval = bestValue = to_static_eval(newEval);
         }