Use nullMove only through MovePicker.

No functional change.

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

src/movepick.cpp

@@ -44,6 +44,7 @@ namespace {
 
   CACHE_LINE_ALIGNMENT
   const MovegenPhaseT MainSearchPhaseTable[] = { PH_STOP, PH_NULL_MOVE, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
+  const MovegenPhaseT MainSearchNoNullPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
   const MovegenPhaseT EvasionsPhaseTable[] = { PH_STOP, PH_EVASIONS, PH_STOP};
   const MovegenPhaseT QsearchWithChecksPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
   const MovegenPhaseT QsearchWithoutChecksPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
@@ -79,7 +80,7 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
   if (p.is_check())
       phasePtr = EvasionsPhaseTable;
   else if (d > Depth(0))
-      phasePtr = MainSearchPhaseTable;
+      phasePtr = useNullMove ? MainSearchPhaseTable : MainSearchNoNullPhaseTable;
   else if (d == Depth(0))
       phasePtr = QsearchWithChecksPhaseTable;
   else
@@ -116,7 +117,7 @@ Move MovePicker::get_next_move() {
     switch (*phasePtr) {
 
     case PH_NULL_MOVE:
-        break;
+        return MOVE_NULL;
 
     case PH_TT_MOVES:
         movesPicked = 0; // This is used as index to ttMoves[]

src/search.cpp

@@ -1288,8 +1288,49 @@ namespace {
                         &&  ok_to_do_nullmove(pos)
                         &&  approximateEval >= beta - NullMoveMargin);
 
+    // Null move search not allowed, try razoring
+    if (    !useNullMove
+         && !value_is_mate(beta)
+         && depth < RazorDepth
+         && approximateEval < beta - RazorApprMargins[int(depth) - 2]
+         && ss[ply - 1].currentMove != MOVE_NULL
+         && ttMove == MOVE_NONE
+         && !pos.has_pawn_on_7th(pos.side_to_move()))
+    {
+        Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
+        if (v < beta - RazorMargins[int(depth) - 2])
+          return v;
+    }
+
+    // Go with internal iterative deepening if we don't have a TT move
+    if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
+        evaluate(pos, ei, threadID) >= beta - IIDMargin)
+    {
+        search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
+        ttMove = ss[ply].pv[ply];
+    }
+
+    // Initialize a MovePicker object for the current position, and prepare
+    // to search all moves.
+    MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], useNullMove);
+
+    Move move, movesSearched[256];
+    int moveCount = 0;
+    Value value, bestValue = -VALUE_INFINITE;
+    Bitboard dcCandidates = mp.discovered_check_candidates();
+    Value futilityValue = VALUE_NONE;
+    bool useFutilityPruning =   depth < SelectiveDepth
+                             && !isCheck;
+
+    // Loop through all legal moves until no moves remain or a beta cutoff
+    // occurs.
+    while (   bestValue < beta
+           && (move = mp.get_next_move()) != MOVE_NONE
+           && !thread_should_stop(threadID))
+    {
+
       // Null move search
-    if (useNullMove)
+      if (move == MOVE_NULL)
       {
           ss[ply].currentMove = MOVE_NULL;
 
@@ -1326,47 +1367,9 @@ namespace {
                   && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
                   return beta - 1;
           }
-    }
+          continue;
-    // Null move search not allowed, try razoring
-    if (    !useNullMove
-         && !value_is_mate(beta)
-         && depth < RazorDepth
-         && approximateEval < beta - RazorApprMargins[int(depth) - 2]
-         && ss[ply - 1].currentMove != MOVE_NULL
-         && ttMove == MOVE_NONE
-         && !pos.has_pawn_on_7th(pos.side_to_move()))
-    {
-        Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
-        if (v < beta - RazorMargins[int(depth) - 2])
-          return v;
       }
 
-    // Go with internal iterative deepening if we don't have a TT move
-    if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
-        evaluate(pos, ei, threadID) >= beta - IIDMargin)
-    {
-        search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
-        ttMove = ss[ply].pv[ply];
-    }
-
-    // Initialize a MovePicker object for the current position, and prepare
-    // to search all moves.
-    MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
-
-    Move move, movesSearched[256];
-    int moveCount = 0;
-    Value value, bestValue = -VALUE_INFINITE;
-    Bitboard dcCandidates = mp.discovered_check_candidates();
-    Value futilityValue = VALUE_NONE;
-    bool useFutilityPruning =   depth < SelectiveDepth
-                             && !isCheck;
-
-    // Loop through all legal moves until no moves remain or a beta cutoff
-    // occurs.
-    while (   bestValue < beta
-           && (move = mp.get_next_move()) != MOVE_NONE
-           && !thread_should_stop(threadID))
-    {
       assert(move_is_ok(move));
 
       bool singleReply = (isCheck && mp.number_of_moves() == 1);