From d9c7cad6302ddeff9f8a32a3fe66359c556a868e Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 17 Nov 2013 09:12:19 +0100
Subject: [PATCH] Retire quietsSearched[]

Use MovePicker moves[] to access already tried
quiet moves. A bit of care shall be taken
to avoid calling stage_moves() when we are still
at ttMove stage, because moves are yet to be
generated. Actually our staging move generation
makes this code a bit more tricky than what I'd
like, but removing an ausiliary redundant
array like quietsSearched[] is a good thing.

Idea by DiscoCheck

bench: 9355734
---
 src/movepick.cpp |  9 +++++++++
 src/movepick.h   |  1 +
 src/search.cpp   | 16 ++++++----------
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 8baf32a4..06ea5e25 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -140,6 +140,15 @@ MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, Piece
 }
 
 
+/// stage_moves() returns a pointer to the beginning of moves array. It
+/// is used to access already tried quiet moves when updating history.
+
+const ExtMove* MovePicker::stage_moves() const {
+  assert(stage == KILLERS_S1 || stage == QUIETS_1_S1 || stage == QUIETS_2_S1);
+  return stage == KILLERS_S1 ? killers : moves;
+}
+
+
 /// score() assign a numerical move ordering score to each move in a move list.
 /// The moves with highest scores will be picked first.
 template<>
diff --git a/src/movepick.h b/src/movepick.h
index c444615f..0a48c82d 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -88,6 +88,7 @@ public:
   MovePicker(const Position&, Move, const HistoryStats&, PieceType);
   MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Search::Stack*);
 
+  const ExtMove* stage_moves() const;
   template<bool SpNode> Move next_move();
 
 private:
diff --git a/src/search.cpp b/src/search.cpp
index f1ab80f2..5aeb9a87 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -484,7 +484,6 @@ namespace {
     assert(PvNode || (alpha == beta - 1));
     assert(depth > DEPTH_ZERO);
 
-    Move quietsSearched[64];
     StateInfo st;
     const TTEntry *tte;
     SplitPoint* splitPoint;
@@ -494,7 +493,7 @@ namespace {
     Value bestValue, value, ttValue, eval, nullValue, futilityValue;
     bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
     bool captureOrPromotion, dangerous, doFullDepthSearch;
-    int moveCount, quietCount;
+    int moveCount;
 
     // Step 1. Initialize node
     Thread* thisThread = pos.this_thread();
@@ -515,7 +514,7 @@ namespace {
         goto moves_loop;
     }
 
-    moveCount = quietCount = 0;
+    moveCount = 0;
     bestValue = -VALUE_INFINITE;
     ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
     ss->ply = (ss-1)->ply + 1;
@@ -901,8 +900,6 @@ moves_loop: // When in check and at SpNode search starts from here
 
       pvMove = PvNode && moveCount == 1;
       ss->currentMove = move;
-      if (!SpNode && !captureOrPromotion && quietCount < 64)
-          quietsSearched[quietCount++] = move;
 
       // Step 14. Make the move
       pos.do_move(move, st, ci, givesCheck);
@@ -1077,11 +1074,10 @@ moves_loop: // When in check and at SpNode search starts from here
         // played non-capture moves.
         Value bonus = Value(int(depth) * int(depth));
         History.update(pos.moved_piece(bestMove), to_sq(bestMove), bonus);
-        for (int i = 0; i < quietCount - 1; ++i)
-        {
-            Move m = quietsSearched[i];
-            History.update(pos.moved_piece(m), to_sq(m), -bonus);
-        }
+
+        if (bestMove != ttMove)
+            for (const ExtMove* em = mp.stage_moves(); em->move != bestMove; ++em)
+                History.update(pos.moved_piece(em->move), to_sq(em->move), -bonus);
 
         if (is_ok((ss-1)->currentMove))
             Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove);
-- 
2.39.2