Remove Movepick::move (#2085)

The "move" class variable is Movepick is removed (removes some abstraction) which saves a few assignment operations, and the effects of "filter" is limited to the current move (movePtr). The resulting code is a bit more verbose, but it is also more clear what is going on. This version is NOT tested, but is substantially similar to:

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 29191 W: 6474 L: 6367 D: 16350
http://tests.stockfishchess.org/tests/view/5ca7aab50ebc5925cf006e50

This is a non-functional simplification.

src/movepick.cpp

@@ -139,12 +139,12 @@ Move MovePicker::select(Pred filter) {
       if (T == Best)
           std::swap(*cur, *std::max_element(cur, endMoves));
 
-      move = *cur++;
+      if (*cur != ttMove && filter())
+          return *cur++;
 
-      if (move != ttMove && filter())
-          return move;
+      cur++;
   }
-  return move = MOVE_NONE;
+  return MOVE_NONE;
 }
 
 /// MovePicker::next_move() is the most important method of the MovePicker class. It
@@ -174,10 +174,10 @@ top:
 
   case GOOD_CAPTURE:
       if (select<Best>([&](){
-                       return pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)) ?
+                       return pos.see_ge(*cur, Value(-55 * cur->value / 1024)) ?
                               // Move losing capture to endBadCaptures to be tried later
-                              true : (*endBadCaptures++ = move, false); }))
-          return move;
+                              true : (*endBadCaptures++ = *cur, false); }))
+          return *(cur - 1);
 
       // Prepare the pointers to loop over the refutations array
       cur = std::begin(refutations);
@@ -192,10 +192,10 @@ top:
       /* fallthrough */
 
   case REFUTATION:
-      if (select<Next>([&](){ return    move != MOVE_NONE
-                                    && !pos.capture(move)
-                                    &&  pos.pseudo_legal(move); }))
-          return move;
+      if (select<Next>([&](){ return    *cur != MOVE_NONE
+                                    && !pos.capture(*cur)
+                                    &&  pos.pseudo_legal(*cur); }))
+          return *(cur - 1);
       ++stage;
       /* fallthrough */
 
@@ -210,10 +210,10 @@ top:
 
   case QUIET:
       if (   !skipQuiets
-          && select<Next>([&](){return   move != refutations[0]
-                                      && move != refutations[1]
-                                      && move != refutations[2];}))
-          return move;
+          && select<Next>([&](){return   *cur != refutations[0].move
+                                      && *cur != refutations[1].move
+                                      && *cur != refutations[2].move;}))
+          return *(cur - 1);
 
       // Prepare the pointers to loop over the bad captures
       cur = moves;
@@ -237,12 +237,12 @@ top:
       return select<Best>([](){ return true; });
 
   case PROBCUT:
-      return select<Best>([&](){ return pos.see_ge(move, threshold); });
+      return select<Best>([&](){ return pos.see_ge(*cur, threshold); });
 
   case QCAPTURE:
       if (select<Best>([&](){ return   depth > DEPTH_QS_RECAPTURES
-                                    || to_sq(move) == recaptureSquare; }))
-          return move;
+                                    || to_sq(*cur) == recaptureSquare; }))
+          return *(cur - 1);
 
       // If we did not find any move and we do not try checks, we have finished
       if (depth != DEPTH_QS_CHECKS)

src/movepick.h

@@ -142,7 +142,6 @@ private:
   Move ttMove;
   ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
   int stage;
-  Move move;
   Square recaptureSquare;
   Value threshold;
   Depth depth;