Return static eval when reaching MAX_PLY

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 95f1332ed1ddb6e1ca743e006cdf1039bcd034d8..ad13c4ba304c1a898d0a5684504d68c7e7fee47b 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -51,12 +51,6 @@ using std::string;
 using Eval::evaluate;
 using namespace Search;
 
-// Fast wrapper for common case of pos.gives_check()
-#define FAST_GIVES_CHECK(pos, m, ci) \
-    ((type_of(m) == NORMAL && ci.dcCandidates == 0) \
-       ? (ci.checkSq[type_of(pos.piece_on(from_sq(m)))] & to_sq(m)) \
-          : pos.gives_check(m, ci))
-
 namespace {
 
   // Set to true to force running with one thread. Used for debugging
@@ -160,10 +154,10 @@ void Search::init() {
 /// Search::perft() is our utility to verify move generation. All the leaf nodes
 /// up to the given depth are generated and counted and the sum returned.
 
-static size_t perft(Position& pos, Depth depth) {
+static uint64_t perft(Position& pos, Depth depth) {
 
   StateInfo st;
-  size_t cnt = 0;
+  uint64_t cnt = 0;
   CheckInfo ci(pos);
   const bool leaf = depth == 2 * ONE_PLY;
 
@@ -176,7 +170,7 @@ static size_t perft(Position& pos, Depth depth) {
   return cnt;
 }
 
-size_t Search::perft(Position& pos, Depth depth) {
+uint64_t Search::perft(Position& pos, Depth depth) {
   return depth > ONE_PLY ? ::perft(pos, depth) : MoveList<LEGAL>(pos).size();
 }
 
@@ -326,7 +320,7 @@ namespace {
     while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
     {
         // Age out PV variability metric
-        BestMoveChanges *= 0.8;
+        BestMoveChanges *= 0.5;
 
         // Save the last iteration's scores before first PV line is searched and
         // all the move scores except the (new) PV are set to -VALUE_INFINITE.
@@ -435,11 +429,10 @@ namespace {
             if (depth > 4 && depth < 50 &&  PVSize == 1)
                 TimeMgr.pv_instability(BestMoveChanges);
 
-            // Stop the search if only one legal move is available or most
-            // of the available time has been used. We probably don't have
-            // enough time to search the first move at the next iteration anyway.
+            // Stop the search if only one legal move is available or all
+            // of the available time has been used.
             if (   RootMoves.size() == 1
-                || IterationTime > (TimeMgr.available_time() * 62) / 100)
+                || IterationTime > TimeMgr.available_time() )
                 stop = true;
 
             if (stop)
@@ -519,7 +512,7 @@ namespace {
     {
         // Step 2. Check for aborted search and immediate draw
         if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
-            return DrawValue[pos.side_to_move()];
+            return ss->ply > MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
 
         // Step 3. Mate distance pruning. Even if we mate at the next move our score
         // would be at best mate_in(ss->ply+1), but if alpha is already bigger because
@@ -646,8 +639,24 @@ namespace {
         (ss+1)->skipNullMove = false;
         pos.undo_null_move();
 
-        if (nullValue >= beta) // Do not return unproven mate scores
-            return nullValue >= VALUE_MATE_IN_MAX_PLY ? beta : nullValue;
+        if (nullValue >= beta)
+        {
+            // Do not return unproven mate scores
+            if (nullValue >= VALUE_MATE_IN_MAX_PLY)
+                nullValue = beta;
+
+            if (depth < 12 * ONE_PLY)
+                return nullValue;
+
+            // 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)
+                                        :  search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
+            ss->skipNullMove = false;
+
+            if (v >= beta)
+                return nullValue;
+        }
     }
 
     // Step 9. ProbCut (skipped when in check)
@@ -760,7 +769,11 @@ moves_loop: // When in check and at SpNode search starts from here
 
       ext = DEPTH_ZERO;
       captureOrPromotion = pos.capture_or_promotion(move);
-      givesCheck = FAST_GIVES_CHECK(pos, move, ci);
+
+      givesCheck =  type_of(move) == NORMAL && !ci.dcCandidates
+                  ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+                  : pos.gives_check(move, ci);
+
       dangerous =   givesCheck
                  || type_of(move) != NORMAL
                  || pos.advanced_pawn_push(move);
@@ -1065,7 +1078,7 @@ moves_loop: // When in check and at SpNode search starts from here
 
     // Check for an instant draw or if the maximum ply has been reached
     if (pos.is_draw() || ss->ply > MAX_PLY)
-        return DrawValue[pos.side_to_move()];
+        return ss->ply > MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
 
     // Decide whether or not to include checks: this fixes also the type of
     // TT entry depth that we are going to use. Note that in qsearch we use
@@ -1140,7 +1153,9 @@ moves_loop: // When in check and at SpNode search starts from here
     {
       assert(is_ok(move));
 
-      givesCheck = FAST_GIVES_CHECK(pos, move, ci);
+      givesCheck =  type_of(move) == NORMAL && !ci.dcCandidates
+                  ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+                  : pos.gives_check(move, ci);
 
       // Futility pruning
       if (   !PvNode
@@ -1612,9 +1627,8 @@ void check_time() {
   Time::point elapsed = Time::now() - SearchTime;
   bool stillAtFirstMove =    Signals.firstRootMove
                          && !Signals.failedLowAtRoot
-                         && (   elapsed > TimeMgr.available_time()
-                             || (   elapsed > (TimeMgr.available_time() * 62) / 100
-                                 && elapsed > IterationTime * 1.4));
+                         &&  elapsed > TimeMgr.available_time()
+                         &&  elapsed > IterationTime * 1.4;
 
   bool noMoreTime =   elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
                    || stillAtFirstMove;