Tweak history updates

In general the history update bonus is slightly decreased by 11% which gives a slower saturation speed.
In addition only for main history the divisor is halfed (used history values are doubled to maintain same maximum)
which have an effect in the opposite direction on saturation speed.

STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.50>
Total: 157088 W: 42673 L: 42168 D: 72247
Ptnml(0-2): 857, 17346, 41642, 17833, 866
https://tests.stockfishchess.org/tests/view/62e5517ab383a712b13867c5

LTC:
LLR: 2.94 (-2.94,2.94) <0.50,3.00>
Total: 325592 W: 88705 L: 87753 D: 149134
Ptnml(0-2): 594, 32288, 96076, 33248, 590
https://tests.stockfishchess.org/tests/view/62e5e4f4b383a712b1387d53

closes https://github.com/official-stockfish/Stockfish/pull/4119

Bench: 5518728

diff --git a/src/movepick.cpp b/src/movepick.cpp
index b0166c6e962b55a169f75ce6f6abbee65b4e029b..60d041ab9c72837326c872491383abb89cffd895 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -137,7 +137,7 @@ void MovePicker::score() {
                    +     (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
 
       else if constexpr (Type == QUIETS)
-          m.value =      (*mainHistory)[pos.side_to_move()][from_to(m)]
+          m.value =  2 * (*mainHistory)[pos.side_to_move()][from_to(m)]
                    + 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
                    +     (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
                    +     (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)]
@@ -155,7 +155,7 @@ void MovePicker::score() {
               m.value =  PieceValue[MG][pos.piece_on(to_sq(m))]
                        - Value(type_of(pos.moved_piece(m)));
           else
-              m.value =      (*mainHistory)[pos.side_to_move()][from_to(m)]
+              m.value =  2 * (*mainHistory)[pos.side_to_move()][from_to(m)]
                        + 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
                        - (1 << 28);
       }

diff --git a/src/movepick.h b/src/movepick.h
index 6b3c08c7a0d3b19abf1643c994ab395a03f14cba..979709ae682885baa073488b1e335c701abfc8ea 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -87,7 +87,7 @@ enum StatsType { NoCaptures, Captures };
 /// ordering decisions. It uses 2 tables (one for each color) indexed by
 /// the move's from and to squares, see www.chessprogramming.org/Butterfly_Boards
 /// (~11 elo)
-typedef Stats<int16_t, 14365, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyHistory;
+typedef Stats<int16_t, 7183, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyHistory;
 
 /// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
 /// move, see www.chessprogramming.org/Countermove_Heuristic

diff --git a/src/search.cpp b/src/search.cpp
index 004d061b7b6929afee75d82ab6fb1face7a54190..9b747e78e41fd96f86e1592b3b2bf88b50cf79c3 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -81,7 +81,7 @@ namespace {
 
   // History and stats update bonus, based on depth
   int stat_bonus(Depth d) {
-    return std::min((9 * d + 270) * d - 311 , 2145);
+    return std::min((8 * d + 240) * d - 276 , 1907);
   }
 
   // Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -1033,7 +1033,7 @@ moves_loop: // When in check, search starts here
                   && history < -3875 * (depth - 1))
                   continue;
 
-              history += thisThread->mainHistory[us][from_to(move)];
+              history += 2 * thisThread->mainHistory[us][from_to(move)];
 
               // Futility pruning: parent node (~9 Elo)
               if (   !ss->inCheck
@@ -1171,7 +1171,7 @@ moves_loop: // When in check, search starts here
           if ((ss+1)->cutoffCnt > 3 && !PvNode)
               r++;
 
-          ss->statScore =  thisThread->mainHistory[us][from_to(move)]
+          ss->statScore =  2 * thisThread->mainHistory[us][from_to(move)]
                          + (*contHist[0])[movedPiece][to_sq(move)]
                          + (*contHist[1])[movedPiece][to_sq(move)]
                          + (*contHist[3])[movedPiece][to_sq(move)]