Revert "null move reorder" series

Does not seem to improve on the standard, latest results
from Joona after 2040 games are negative:

Orig - Mod: 454 - 424 - 1162

And is more or less the same I got few days ago.

So revert for now.

Verified same functionality of 595a90dfd

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

src/movepick.cpp

@@ -40,9 +40,7 @@
 namespace {
 
   CACHE_LINE_ALIGNMENT
-  const MovegenPhaseT MainSearchPhaseTable[] = { PH_NULL_MOVE, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
+  const MovegenPhaseT MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
-  const MovegenPhaseT MainSearchNoNullPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
-  const MovegenPhaseT LowSearchPhaseTable[]  = { PH_TT_MOVES, PH_NULL_MOVE, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
   const MovegenPhaseT EvasionsPhaseTable[] = { PH_EVASIONS, PH_STOP};
   const MovegenPhaseT QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
   const MovegenPhaseT QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
@@ -62,7 +60,7 @@ namespace {
 /// move ordering is at the current node.
 
 MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
-                       const History& h, SearchStack* ss, bool useNullMove) : pos(p), H(h) {
+                       const History& h, SearchStack* ss) : pos(p), H(h) {
   ttMoves[0].move = ttm;
   if (ss)
   {
@@ -82,10 +80,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
 
   if (p.is_check())
       phasePtr = EvasionsPhaseTable;
-  else if (d >= Depth(3 * OnePly))
-      phasePtr = useNullMove ? MainSearchPhaseTable : MainSearchNoNullPhaseTable;
   else if (d > Depth(0))
-      phasePtr = useNullMove ? LowSearchPhaseTable : MainSearchNoNullPhaseTable;
+      phasePtr = MainSearchPhaseTable;
   else if (d == Depth(0))
       phasePtr = QsearchWithChecksPhaseTable;
   else
@@ -105,9 +101,6 @@ void MovePicker::go_next_phase() {
   phase = *(++phasePtr);
   switch (phase) {
 
-  case PH_NULL_MOVE:
-      return;
-
   case PH_TT_MOVES:
       curMove = ttMoves;
       lastMove = curMove + 2;
@@ -258,10 +251,6 @@ Move MovePicker::get_next_move() {
   {
       switch (phase) {
 
-      case PH_NULL_MOVE:
-          go_next_phase();
-          return MOVE_NULL;
-
       case PH_TT_MOVES:
           while (curMove != lastMove)
           {

src/movepick.h

@@ -38,7 +38,6 @@
 struct SearchStack;
 
 enum MovegenPhase {
-  PH_NULL_MOVE,      // Null move
   PH_TT_MOVES,       // Transposition table move and mate killer
   PH_GOOD_CAPTURES,  // Queen promotions and captures with SEE values >= 0
   PH_KILLERS,        // Killer moves from the current ply
@@ -65,7 +64,7 @@ class MovePicker {
   MovePicker& operator=(const MovePicker&); // silence a warning under MSVC
 
 public:
-  MovePicker(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss = NULL, bool useNullMove = false);
+  MovePicker(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss = NULL);
   Move get_next_move();
   Move get_next_move(Lock& lock);
   int number_of_moves() const;

src/search.cpp

@@ -1281,56 +1281,13 @@ namespace {
     bool mateThreat = false;
     bool isCheck = pos.is_check();
 
-    bool useNullMove = (    allowNullmove
+    // Null move search
+    if (    allowNullmove
         &&  depth > OnePly
         && !isCheck
         && !value_is_mate(beta)
         &&  ok_to_do_nullmove(pos)
-                        &&  approximateEval >= beta - NullMoveMargin);
+        &&  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 (move == MOVE_NULL)
     {
         ss[ply].currentMove = MOVE_NULL;
 
@@ -1367,9 +1324,46 @@ namespace {
                 && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
                 return beta - 1;
         }
-          continue;
+    }
+    // Null move search not allowed, try razoring
+    else if (   !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);