Allow inCheck pruning

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c09e23d687a19f34d4b74be3145805fd883bafb1..64cdb325ebce53c3a785747767cf76109b5daa31 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -29,6 +29,7 @@
 #include "misc.h"
 #include "movegen.h"
 #include "movepick.h"
+#include "position.h"
 #include "search.h"
 #include "timeman.h"
 #include "thread.h"
@@ -505,7 +506,7 @@ void Thread::search() {
 
               if (   rootMoves.size() == 1
                   || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628
-                  || (mainThread->easyMovePlayed = doEasyMove))
+                  || (mainThread->easyMovePlayed = doEasyMove, doEasyMove))
               {
                   // If we are allowed to ponder do not stop the search now but
                   // keep pondering until the GUI sends "ponderhit" or "stop".
@@ -727,8 +728,7 @@ namespace {
         &&  ttMove == MOVE_NONE
         &&  eval + razor_margin[depth / ONE_PLY] <= alpha)
     {
-        if (   depth <= ONE_PLY
-            && eval + razor_margin[3 * ONE_PLY] <= alpha)
+        if (depth <= ONE_PLY)
             return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
 
         Value ralpha = alpha - razor_margin[depth / ONE_PLY];
@@ -844,8 +844,7 @@ moves_loop: // When in check search starts from here
     singularExtensionNode =   !rootNode
                            &&  depth >= 8 * ONE_PLY
                            &&  ttMove != MOVE_NONE
-                       /*  &&  ttValue != VALUE_NONE Already implicit in the next condition */
-                           &&  abs(ttValue) < VALUE_KNOWN_WIN
+                           &&  ttValue != VALUE_NONE
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
@@ -903,7 +902,7 @@ moves_loop: // When in check search starts from here
           && !extension
           &&  pos.legal(move))
       {
-          Value rBeta = ttValue - 2 * depth / ONE_PLY;
+          Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
           Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
           ss->excludedMove = move;
           ss->skipEarlyPruning = true;
@@ -920,8 +919,7 @@ moves_loop: // When in check search starts from here
 
       // Step 13. Pruning at shallow depth
       if (  !rootNode
-         && !inCheck
-         &&  bestValue > VALUE_MATED_IN_MAX_PLY)
+          &&  bestValue > VALUE_MATED_IN_MAX_PLY)
       {
           if (   !captureOrPromotion
               && !givesCheck
@@ -1122,6 +1120,9 @@ moves_loop: // When in check search starts from here
     // All legal moves have been searched and if there are no legal moves, it
     // must be a mate or a stalemate. If we are in a singular extension search then
     // return a fail low score.
+
+    assert(moveCount || !inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
+
     if (!moveCount)
         bestValue = excludedMove ? alpha
                    :     inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
@@ -1588,13 +1589,16 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
 /// fail high at root. We try hard to have a ponder move to return to the GUI,
 /// otherwise in case of 'ponder on' we have nothing to think on.
 
-bool RootMove::extract_ponder_from_tt(Position& pos)
-{
+bool RootMove::extract_ponder_from_tt(Position& pos) {
+
     StateInfo st;
     bool ttHit;
 
     assert(pv.size() == 1);
 
+    if (!pv[0])
+        return false;
+
     pos.do_move(pv[0], st, pos.gives_check(pv[0]));
     TTEntry* tte = TT.probe(pos.key(), ttHit);