Incremental Futility Margin

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 44c29ec878209a882c27f5880878443ac32a0081..b420fb905203770005d92c9725b27ae99c4b938f 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -176,6 +176,9 @@ namespace {
   // and near frontier nodes.
   const Value FutilityMarginQS = Value(0x80);
 
+  // Each move futility margin is decreased
+  const Value IncrementalFutilityMargin = Value(0xA);
+
   // Remaining depth:                  1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
   const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270),
   //                                   4 ply         4.5 ply       5 ply         5.5 ply       6 ply         6.5 ply
@@ -310,7 +313,7 @@ namespace {
              Value *alpha, Value *beta, Value *bestValue,
              const Value futilityValue, const Value approximateValue,
              Depth depth, int *moves,
-             MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode);
+             MovePicker *mp, int master, bool pvNode);
   void wake_sleeping_threads();
 
 #if !defined(_MSC_VER)
@@ -333,14 +336,14 @@ namespace {
 int perft(Position& pos, Depth depth)
 {
     Move move;
-    MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H);
     int sum = 0;
+    MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H);
 
     // If we are at the last ply we don't need to do and undo
     // the moves, just to count them.
     if (depth <= OnePly) // Replace with '<' to test also qsearch
     {
-        while ((move = mp.get_next_move()) != MOVE_NONE) sum++;
+        while (mp.get_next_move()) sum++;
         return sum;
     }
 
@@ -348,10 +351,10 @@ int perft(Position& pos, Depth depth)
     CheckInfo ci(pos);
     while ((move = mp.get_next_move()) != MOVE_NONE)
     {
-      StateInfo st;
-      pos.do_move(move, st, ci.dcCandidates, pos.move_is_check(move, ci));
-      sum += perft(pos, depth - OnePly);
-      pos.undo_move(move);
+        StateInfo st;
+        pos.do_move(move, st, ci, pos.move_is_check(move, ci));
+        sum += perft(pos, depth - OnePly);
+        pos.undo_move(move);
     }
     return sum;
 }
@@ -898,13 +901,14 @@ namespace {
                       << " currmovenumber " << i + 1 << std::endl;
 
         // Decide search depth for this move
+        bool moveIsCheck = pos.move_is_check(move);
         bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
         bool dangerous;
-        ext = extension(pos, move, true, captureOrPromotion, pos.move_is_check(move), false, false, &dangerous);
+        ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
         newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
 
         // Make the move, and search it
-        pos.do_move(move, st, ci.dcCandidates);
+        pos.do_move(move, st, ci, moveIsCheck);
 
         if (i < MultiPV)
         {
@@ -1135,7 +1139,7 @@ namespace {
       newDepth = depth - OnePly + ext;
 
       // Make and search the move
-      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
+      pos.do_move(move, st, ci, moveIsCheck);
 
       if (moveCount == 1) // The first move in list is the PV
           value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
@@ -1208,8 +1212,8 @@ namespace {
           && idle_thread_exists(threadID)
           && !AbortSearch
           && !thread_should_stop(threadID)
-          && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, VALUE_NONE, depth,
-                   &moveCount, &mp, ci.dcCandidates, threadID, true))
+          && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, VALUE_NONE,
+                   depth, &moveCount, &mp, threadID, true))
           break;
     }
 
@@ -1259,7 +1263,7 @@ namespace {
     const TTEntry* tte;
     Move ttMove, move;
     Depth ext, newDepth;
-    Value approximateEval, nullValue, value, futilityValue;
+    Value approximateEval, nullValue, value, futilityValue, futilityValueScaled;
     bool isCheck, useFutilityPruning, singleReply, moveIsCheck, captureOrPromotion, dangerous;
     bool mateThreat = false;
     int moveCount = 0;
@@ -1313,7 +1317,13 @@ namespace {
         ss[ply].currentMove = MOVE_NULL;
 
         pos.do_null_move(st);
-        int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
+
+        // Null move dynamic reduction based on depth
+        int R = (depth >= 5 * OnePly ? 4 : 3);
+
+        // Null move dynamic reduction based on value
+        if (approximateEval - beta > PawnValueMidgame)
+            R++;
 
         nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
 
@@ -1353,8 +1363,9 @@ namespace {
              && 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])
+        Value rbeta = beta - RazorMargins[int(depth) - 2];
+        Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
+        if (v < rbeta)
           return v;
     }
 
@@ -1398,7 +1409,8 @@ namespace {
       // Futility pruning
       if (    useFutilityPruning
           && !dangerous
-          && !captureOrPromotion)
+          && !captureOrPromotion
+          &&  move != ttMove)
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)
@@ -1411,19 +1423,22 @@ namespace {
           {
               if (futilityValue == VALUE_NONE)
                   futilityValue =  evaluate(pos, ei, threadID)
-                                 + FutilityMargins[int(depth) - 2];
+                                 + FutilityMargins[int(depth) - 2]
+                                 + 4*IncrementalFutilityMargin;
+
+              futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin;
 
-              if (futilityValue < beta)
+              if (futilityValueScaled < beta)
               {
-                  if (futilityValue > bestValue)
-                      bestValue = futilityValue;
+                  if (futilityValueScaled > bestValue)
+                      bestValue = futilityValueScaled;
                   continue;
               }
           }
       }
 
       // Make and search the move
-      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
+      pos.do_move(move, st, ci, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
@@ -1468,8 +1483,8 @@ namespace {
           && idle_thread_exists(threadID)
           && !AbortSearch
           && !thread_should_stop(threadID)
-          && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, approximateEval, depth, &moveCount,
-                   &mp, ci.dcCandidates, threadID, false))
+          && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, approximateEval,
+                   depth, &moveCount, &mp, threadID, false))
         break;
     }
 
@@ -1609,6 +1624,7 @@ namespace {
           && !isCheck
           && !pvNode
           && !moveIsCheck
+          &&  move != ttMove
           && !move_is_promotion(move)
           && !pos.move_is_passed_pawn_push(move))
       {
@@ -1635,7 +1651,7 @@ namespace {
           continue;
 
       // Make and search the move
-      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
+      pos.do_move(move, st, ci, moveIsCheck);
       value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
       pos.undo_move(move);
 
@@ -1762,7 +1778,7 @@ namespace {
 
       // Make and search the move.
       StateInfo st;
-      pos.do_move(move, st, sp->dcCandidates, moveIsCheck);
+      pos.do_move(move, st, ci, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
@@ -1868,7 +1884,7 @@ namespace {
 
       // Make and search the move.
       StateInfo st;
-      pos.do_move(move, st, sp->dcCandidates, moveIsCheck);
+      pos.do_move(move, st, ci, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
@@ -2812,7 +2828,7 @@ namespace {
   bool split(const Position& p, SearchStack* sstck, int ply,
              Value* alpha, Value* beta, Value* bestValue, const Value futilityValue,
              const Value approximateEval, Depth depth, int* moves,
-             MovePicker* mp, Bitboard dcCandidates, int master, bool pvNode) {
+             MovePicker* mp, int master, bool pvNode) {
 
     assert(p.is_ok());
     assert(sstck != NULL);
@@ -2849,7 +2865,6 @@ namespace {
     splitPoint->alpha = pvNode? *alpha : (*beta - 1);
     splitPoint->beta = *beta;
     splitPoint->pvNode = pvNode;
-    splitPoint->dcCandidates = dcCandidates;
     splitPoint->bestValue = *bestValue;
     splitPoint->futilityValue = futilityValue;
     splitPoint->approximateEval = approximateEval;