Assorted trivial cleanups June 2019

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index e008bec1e45d8a063cca7d05dd803411d7cb38c6..e6446768066afa33f95d8b6f2aec9faa62abc90e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -335,7 +335,12 @@ void Thread::search() {
   beta = VALUE_INFINITE;
 
   multiPV = Options["MultiPV"];
-  Skill skill(Options["Skill Level"]);
+  // Pick integer skill levels, but non-deterministically round up or down
+  // such that the average integer skill corresponds to the input floating point one.
+  PRNG rng(now());
+  int intLevel = int(Options["Skill Level"]) +
+        ((Options["Skill Level"] - int(Options["Skill Level"])) * 1024 > rng.rand<unsigned>() % 1024  ? 1 : 0);
+  Skill skill(intLevel);
 
   // When playing with strength handicap enable MultiPV search that we will
   // use behind the scenes to retrieve a set of possible moves.
@@ -734,7 +739,7 @@ namespace {
     }
     else if (ttHit)
     {
-        // Never assume anything on values stored in TT
+        // Never assume anything about values stored in TT
         ss->staticEval = eval = tte->eval();
         if (eval == VALUE_NONE)
             ss->staticEval = eval = evaluate(pos);
@@ -973,7 +978,7 @@ moves_loop: // When in check, search starts from here
 
       // Check extension (~2 Elo)
       else if (    givesCheck
-               && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
+               && (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
           extension = ONE_PLY;
 
       // Castling extension
@@ -1008,7 +1013,7 @@ moves_loop: // When in check, search starts from here
               && !givesCheck
               && (!pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg))
           {
-              // Move count based pruning (~30 Elo)
+              // Move count based pruning
               if (moveCountPruning)
                   continue;
 
@@ -1032,8 +1037,8 @@ moves_loop: // When in check, search starts from here
               if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
                   continue;
           }
-          else if ((!givesCheck || !extension)
-                  && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
+          else if (  (!givesCheck || !extension)
+                   && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
                   continue;
       }
 
@@ -1065,7 +1070,7 @@ moves_loop: // When in check, search starts from here
           Depth r = reduction(improving, depth, moveCount);
 
           // Reduction if other threads are searching this position.
-         if (th.marked())
+          if (th.marked())
               r += ONE_PLY;
 
           // Decrease reduction if position is or has been on the PV
@@ -1110,7 +1115,7 @@ moves_loop: // When in check, search starts from here
                   r += ONE_PLY;
 
               // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-              r -= ss->statScore / 20000 * ONE_PLY;
+              r -= ss->statScore / 16384 * ONE_PLY;
           }
 
           Depth d = clamp(newDepth - r, ONE_PLY, newDepth);
@@ -1336,7 +1341,7 @@ moves_loop: // When in check, search starts from here
     {
         if (ttHit)
         {
-            // Never assume anything on values stored in TT
+            // Never assume anything about values stored in TT
             if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
                 ss->staticEval = bestValue = evaluate(pos);