Clean up step 11

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 56f89456373fc5d6043d8d12fa4d431810aa1d37..b269962f9558f006899b5aca06d8973b1153e1c6 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -158,34 +158,51 @@ namespace {
   };
 
 
-  /// Constants
+  /// Adjustments
 
-  // Search depth at iteration 1
-  const Depth InitialDepth = OnePly;
-
-  // Use internal iterative deepening?
-  const bool UseIIDAtPVNodes = true;
-  const bool UseIIDAtNonPVNodes = true;
+  // Step 6. Razoring
 
-  // Internal iterative deepening margin. At Non-PV moves, when
-  // UseIIDAtNonPVNodes is true, we do an internal iterative deepening
-  // search when the static evaluation is at most IIDMargin below beta.
-  const Value IIDMargin = Value(0x100);
+  const Depth RazorDepth = 4 * OnePly;
+  inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * d); }
 
-  // Easy move margin. An easy move candidate must be at least this much
-  // better than the second best move.
-  const Value EasyMoveMargin = Value(0x200);
+  // Step 8. Null move search with verification search
 
   // Null move margin. A null move search will not be done if the static
   // evaluation of the position is more than NullMoveMargin below beta.
   const Value NullMoveMargin = Value(0x200);
 
-  // If the TT move is at least SingleReplyMargin better then the
+  // Step 9. Internal iterative deepening
+
+  const Depth IIDDepthAtPVNodes = 5 * OnePly;
+  const Depth IIDDepthAtNonPVNodes = 8 * OnePly;
+
+  // Internal iterative deepening margin. At Non-PV nodes
+  // we do an internal iterative deepening
+  // search when the static evaluation is at most IIDMargin below beta.
+  const Value IIDMargin = Value(0x100);
+
+  // Step 11. Decide the new search depth
+
+  // Extensions. Configurable UCI options.
+  // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
+  Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
+  Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
+
+  const Depth SingularExtensionDepthAtPVNodes = 6 * OnePly;
+  const Depth SingularExtensionDepthAtNonPVNodes = 8 * OnePly;
+
+  // If the TT move is at least SingularExtensionMargin better then the
   // remaining ones we will extend it.
-  const Value SingleReplyMargin = Value(0x20);
+  const Value SingularExtensionMargin = Value(0x20);
 
-  // Depth limit for razoring
-  const Depth RazorDepth = 4 * OnePly;
+
+
+  // Search depth at iteration 1
+  const Depth InitialDepth = OnePly;
+
+  // Easy move margin. An easy move candidate must be at least this much
+  // better than the second best move.
+  const Value EasyMoveMargin = Value(0x200);
 
   /// Lookup tables initialized at startup
 
@@ -215,10 +232,6 @@ namespace {
   const Value LSNValue = value_from_centipawns(200);
   bool loseOnTime = false;
 
-  // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
-  Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
-  Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
-
   // Iteration counters
   int Iteration;
 
@@ -1096,8 +1109,7 @@ namespace {
     // Step 8. Null move search with verification search (is omitted in PV nodes)
 
     // Step 9. Internal iterative deepening
-    if (   UseIIDAtPVNodes
-        && depth >= 5*OnePly
+    if (   depth >= IIDDepthAtPVNodes
         && ttMove == MOVE_NONE)
     {
         search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
@@ -1129,7 +1141,7 @@ namespace {
       // Singular extension search. We extend the TT move if its value is much better than
       // its siblings. To verify this we do a reduced search on all the other moves but the
       // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
-      if (   depth >= 6 * OnePly
+      if (   depth >= SingularExtensionDepthAtPVNodes
           && tte
           && move == tte->move()
           && ext < OnePly
@@ -1140,9 +1152,9 @@ namespace {
 
           if (abs(ttValue) < VALUE_KNOWN_WIN)
           {
-              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
+              Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
 
-              if (excValue < ttValue - SingleReplyMargin)
+              if (excValue < ttValue - SingularExtensionMargin)
                   ext = OnePly;
           }
       }
@@ -1332,15 +1344,15 @@ namespace {
     if (   !value_is_mate(beta)
         && !isCheck
         && depth < RazorDepth
-        && refinedValue < beta - (0x200 + 16 * depth)
+        && refinedValue < beta - razor_margin(depth)
         && ss[ply - 1].currentMove != MOVE_NULL
         && ttMove == MOVE_NONE
         && !pos.has_pawn_on_7th(pos.side_to_move()))
     {
-        Value rbeta = beta - (0x200 + 16 * depth);
+        Value rbeta = beta - razor_margin(depth);
         Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
         if (v < rbeta)
-          return v; //FIXME: Logically should be: return (v + 0x200 + 16 * depth);
+          return v; //FIXME: Logically should be: return (v + razor_margin(depth));
     }
 
     // Step 7. Static null move pruning
@@ -1406,8 +1418,10 @@ namespace {
     }
 
     // Step 9. Internal iterative deepening
-    if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
-        !isCheck && ss[ply].eval >= beta - IIDMargin)
+    if (   depth >= IIDDepthAtNonPVNodes
+        && ttMove == MOVE_NONE
+        && !isCheck
+        && ss[ply].eval >= beta - IIDMargin)
     {
         search(pos, ss, beta, depth/2, ply, false, threadID);
         ttMove = ss[ply].pv[ply];
@@ -1440,7 +1454,7 @@ namespace {
       // Singular extension search. We extend the TT move if its value is much better than
       // its siblings. To verify this we do a reduced search on all the other moves but the
       // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
-      if (   depth >= 8 * OnePly
+      if (   depth >= SingularExtensionDepthAtNonPVNodes
           && tte
           && move == tte->move()
           && !excludedMove // Do not allow recursive single-reply search
@@ -1452,9 +1466,9 @@ namespace {
 
           if (abs(ttValue) < VALUE_KNOWN_WIN)
           {
-              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
+              Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
 
-              if (excValue < ttValue - SingleReplyMargin)
+              if (excValue < ttValue - SingularExtensionMargin)
                   ext = OnePly;
           }
       }