Retire MovePickerExt struct

Templetize MovePicker::next_move() member function instead. It
is easier and we also avoid the forwarding of MovePicker() c'tor
arguments in the common case.

Suggested by Rein Halbersma.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/movepick.cpp

@@ -23,6 +23,7 @@
 
 #include "movegen.h"
 #include "movepick.h"
+#include "thread.h"
 
 namespace {
 
@@ -58,13 +59,14 @@ namespace {
 /// move ordering is at the current node.
 
 MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
-                       Search::Stack* ss, Value beta) : pos(p), H(h), depth(d) {
+                       Search::Stack* s, Value beta) : pos(p), H(h), depth(d) {
 
   assert(d > DEPTH_ZERO);
 
   captureThreshold = 0;
   curMove = lastMove = moves;
   lastBadCapture = moves + MAX_MOVES - 1;
+  ss = s;
 
   if (p.in_check())
       phase = EVASION;
@@ -270,10 +272,9 @@ void MovePicker::generate_next() {
 /// It returns a new pseudo legal move every time it is called, until there
 /// are no more moves left. It picks the move with the biggest score from a list
 /// of generated moves taking care not to return the tt move if has already been
-/// searched previously. Note that this function is not thread safe so should be
+/// searched previously.
-/// lock protected by caller when accessed through a shared MovePicker object.
+template<>
-
+Move MovePicker::next_move<false>() {
-Move MovePicker::next_move() {
 
   Move move;
 
@@ -354,3 +355,10 @@ Move MovePicker::next_move() {
       }
   }
 }
+
+
+/// Version of next_move() to use at split point nodes where the move is grabbed
+/// from the split point's shared MovePicker object. This function is not thread
+/// safe so should be lock protected by the caller.
+template<>
+Move MovePicker::next_move<true>() { return ss->sp->mp->next_move<false>(); }

src/movepick.h

@@ -41,7 +41,7 @@ public:
   MovePicker(const Position&, Move, Depth, const History&, Search::Stack*, Value);
   MovePicker(const Position&, Move, Depth, const History&, Square);
   MovePicker(const Position&, Move, const History&, PieceType);
-  Move next_move();
+  template<bool SpNode> Move next_move();
 
 private:
   void score_captures();
@@ -51,6 +51,7 @@ private:
 
   const Position& pos;
   const History& H;
+  Search::Stack* ss;
   Depth depth;
   Move ttMove;
   MoveStack killers[2];

src/search.cpp

@@ -146,25 +146,6 @@ namespace {
   Move do_skill_level();
   string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
 
-  // MovePickerExt class template extends MovePicker and allows to choose at
-  // compile time the proper moves source according to the type of node. In the
-  // default case we simply create and use a standard MovePicker object.
-  template<bool SpNode> struct MovePickerExt : public MovePicker {
-
-    MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
-                  : MovePicker(p, ttm, d, h, ss, b) {}
-  };
-
-  // In case of a SpNode we use split point's shared MovePicker object as moves source
-  template<> struct MovePickerExt<true> : public MovePicker {
-
-    MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
-                  : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
-
-    Move next_move() { return mp->next_move(); }
-    MovePicker* mp;
-  };
-
   // is_dangerous() checks whether a move belongs to some classes of known
   // 'dangerous' moves so that we avoid to prune it.
   FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) {
@@ -779,7 +760,7 @@ namespace {
         MovePicker mp(pos, ttMove, H, pos.captured_piece_type());
         CheckInfo ci(pos);
 
-        while ((move = mp.next_move()) != MOVE_NONE)
+        while ((move = mp.next_move<false>()) != MOVE_NONE)
             if (pos.pl_move_is_legal(move, ci.pinned))
             {
                 ss->currentMove = move;
@@ -808,7 +789,7 @@ namespace {
 
 split_point_start: // At split points actual search starts from here
 
-    MovePickerExt<SpNode> mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
+    MovePicker mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
     CheckInfo ci(pos);
     futilityBase = ss->eval + ss->evalMargin;
     singularExtensionNode =   !RootNode
@@ -822,7 +803,7 @@ split_point_start: // At split points actual search starts from here
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
     while (    bestValue < beta
-           && (move = mp.next_move()) != MOVE_NONE
+           && (move = mp.next_move<SpNode>()) != MOVE_NONE
            && !thisThread->cutoff_occurred()
            && !Signals.stop)
     {
@@ -1213,7 +1194,7 @@ split_point_start: // At split points actual search starts from here
 
     // Loop through the moves until no moves remain or a beta cutoff occurs
     while (   bestValue < beta
-           && (move = mp.next_move()) != MOVE_NONE)
+           && (move = mp.next_move<false>()) != MOVE_NONE)
     {
       assert(is_ok(move));