Introduce static history

The idea of this patch can be described as following: we update static
history stats based on comparison of the static evaluations of the
position before and after the move. If the move increases static evaluation
it's assigned positive bonus, if it decreases static evaluation
it's assigned negative bonus. These stats are used in movepicker
to sort quiet moves.

passed STC
https://tests.stockfishchess.org/tests/view/5fca4c0842a050a89f02cd66
LLR: 3.00 (-2.94,2.94) {-0.25,1.25}
Total: 78152 W: 7409 L: 7171 D: 63572
Ptnml(0-2): 303, 5695, 26873, 5871, 334

passed LTC
https://tests.stockfishchess.org/tests/view/5fca6be442a050a89f02cd75
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 40240 W: 1602 L: 1441 D: 37197
Ptnml(0-2): 19, 1306, 17305, 1475, 15

closes https://github.com/official-stockfish/Stockfish/pull/3253

bench 3845156

diff --git a/src/movepick.cpp b/src/movepick.cpp
index f5e0238..9ca1a21 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -54,9 +54,9 @@ namespace {
 /// ordering is at the current node.
 
 /// MovePicker constructor for the main search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const LowPlyHistory* lp,
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const ButterflyHistory* sh, const LowPlyHistory* lp,
                        const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, const Move* killers, int pl)
-           : pos(p), mainHistory(mh), lowPlyHistory(lp), captureHistory(cph), continuationHistory(ch),
+           : pos(p), mainHistory(mh), staticHistory(sh), lowPlyHistory(lp), captureHistory(cph), continuationHistory(ch),
              ttMove(ttm), refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d), ply(pl) {
 
   assert(d > 0);
@@ -66,9 +66,9 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHist
 }
 
 /// MovePicker constructor for quiescence search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const ButterflyHistory* sh,
                        const CapturePieceToHistory* cph, const PieceToHistory** ch, Square rs)
-           : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), ttMove(ttm), recaptureSquare(rs), depth(d) {
+           : pos(p), mainHistory(mh), staticHistory(sh), captureHistory(cph), continuationHistory(ch), ttMove(ttm), recaptureSquare(rs), depth(d) {
 
   assert(d <= 0);
 
@@ -105,6 +105,7 @@ void MovePicker::score() {
 
       else if (Type == QUIETS)
           m.value =      (*mainHistory)[pos.side_to_move()][from_to(m)]
+                   +     (*staticHistory)[pos.side_to_move()][from_to(m)]
                    + 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
                    + 2 * (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
                    + 2 * (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)]

diff --git a/src/movepick.h b/src/movepick.h
index 4c0ad55..7fe98e4 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -123,10 +123,12 @@ public:
   MovePicker& operator=(const MovePicker&) = delete;
   MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
   MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+                                           const ButterflyHistory*,
                                            const CapturePieceToHistory*,
                                            const PieceToHistory**,
                                            Square);
   MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+                                           const ButterflyHistory*,
                                            const LowPlyHistory*,
                                            const CapturePieceToHistory*,
                                            const PieceToHistory**,
@@ -143,6 +145,7 @@ private:
 
   const Position& pos;
   const ButterflyHistory* mainHistory;
+  const ButterflyHistory* staticHistory;
   const LowPlyHistory* lowPlyHistory;
   const CapturePieceToHistory* captureHistory;
   const PieceToHistory** continuationHistory;

diff --git a/src/search.cpp b/src/search.cpp
index 5254186..ab55969 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -807,6 +807,15 @@ namespace {
         tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
     }
 
+    // Update static history for previous move
+    if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
+    {
+        int bonus = ss->staticEval > -(ss-1)->staticEval + 2 * Tempo ? -stat_bonus(depth) :
+                    ss->staticEval < -(ss-1)->staticEval + 2 * Tempo ? stat_bonus(depth) :
+                    0;
+        thisThread->staticHistory[~us][from_to((ss-1)->currentMove)] << bonus;
+    }
+
     // Step 7. Razoring (~1 Elo)
     if (   !rootNode // The required rootNode PV handling is not available in qsearch
         &&  depth == 1
@@ -964,6 +973,7 @@ moves_loop: // When in check, search starts from here
     Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
 
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
+                                      &thisThread->staticHistory,
                                       &thisThread->lowPlyHistory,
                                       &captureHistory,
                                       contHist,
@@ -1507,6 +1517,7 @@ moves_loop: // When in check, search starts from here
     // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
     // will be generated.
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
+                                      &thisThread->staticHistory,
                                       &thisThread->captureHistory,
                                       contHist,
                                       to_sq((ss-1)->currentMove));

diff --git a/src/thread.cpp b/src/thread.cpp
index 2fbf745..bfcdb65 100644 (file)
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -57,6 +57,7 @@ void Thread::clear() {
 
   counterMoves.fill(MOVE_NONE);
   mainHistory.fill(0);
+  staticHistory.fill(0);
   lowPlyHistory.fill(0);
   captureHistory.fill(0);
 

diff --git a/src/thread.h b/src/thread.h
index 6a73423..c05fa94 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -69,6 +69,7 @@ public:
   Depth rootDepth, completedDepth;
   CounterMoveHistory counterMoves;
   ButterflyHistory mainHistory;
+  ButterflyHistory staticHistory;
   LowPlyHistory lowPlyHistory;
   CapturePieceToHistory captureHistory;
   ContinuationHistory continuationHistory[2][2];