Allow SF to find mates more easily.

Bench: 7698608
jhellis3 · Nov 30, 2014 · c6c152e · c6c152e · bunkbail · Dec 1, 2014
1 parent 314d446
commit c6c152e
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Showing 3 changed files with 27 additions and 1 deletion.
diff --git a/src/movegen.cpp b/src/movegen.cpp
@@ -416,3 +416,22 @@ ExtMove* generate<LEGAL>(const Position& pos, ExtMove* mlist) {
 
   return end;
 }
+
+template<>
+ExtMove* generate<KING_MOVES>(const Position& pos, ExtMove* mlist) {
+
+  ExtMove *end, *cur = mlist;
+  Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
+  Square ksq = pos.king_square(pos.side_to_move());
+
+  end = pos.checkers() ? generate<EVASIONS>(pos, mlist)
+                       : generate<NON_EVASIONS>(pos, mlist);
+  while (cur != end)
+      if (   from_sq(cur->move) == ksq
+          && pos.legal(cur->move, pinned))
+         ++cur;
+      else
+         cur->move = (--end)->move;
+
+  return end;
+}
diff --git a/src/movegen.h b/src/movegen.h
@@ -28,7 +28,8 @@ enum GenType {
   QUIET_CHECKS,
   EVASIONS,
   NON_EVASIONS,
-  LEGAL
+  LEGAL,
+  KING_MOVES
 };
 
 class Position;

diff --git a/src/search.cpp b/src/search.cpp
@@ -621,6 +621,7 @@ namespace {
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY
+        &&  abs(eval) < VALUE_MATE_IN_MAX_PLY
         &&  eval + razor_margin(depth) <= alpha
         &&  ttMove == MOVE_NONE
         && !pos.pawn_on_7th(pos.side_to_move()))
@@ -649,6 +650,7 @@ namespace {
         && !ss->skipNullMove
         &&  depth >= 2 * ONE_PLY
         &&  eval >= beta
+        &&  abs(eval) < VALUE_MATE_IN_MAX_PLY
         &&  pos.non_pawn_material(pos.side_to_move()))
     {
         ss->currentMove = MOVE_NULL;
@@ -674,6 +676,9 @@ namespace {
             if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN)
                 return nullValue;
 
+            if (MoveList<KING_MOVES>(pos).size() < 1 || MoveList<LEGAL>(pos).size() < 6)
+                R = DEPTH_ZERO;
+
             // Do verification search at high depths
             ss->skipNullMove = true;
             Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
@@ -692,6 +697,7 @@ namespace {
     if (   !PvNode
         &&  depth >= 5 * ONE_PLY
         && !ss->skipNullMove
+        &&  abs(eval) < VALUE_MATE_IN_MAX_PLY
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY)
     {
         Value rbeta = std::min(beta + 200, VALUE_INFINITE);