From: Marco Costalba <mcostalba@gmail.com>
Date: Thu, 9 Jun 2011 20:57:42 +0000 (+0100)
Subject: Revert refinedValue in ProbCut
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=a21a110188eed1ff41f2a1535a93b48c654663de;ds=sidebyside

Revert refinedValue in ProbCut

It seems much worst in number of nodes seacrhed to reach
the depth and anyhow does not give any advantage to the
Onno's oroginal one.

So revert by now and perhaps readd when we find something
clearly better.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 7d759f12..61e5527f 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -110,13 +110,13 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h)
   go_next_phase();
 }
 
-MovePicker::MovePicker(const Position& p, Move ttm, const History& h, int threshold)
+MovePicker::MovePicker(const Position& p, Move ttm, const History& h, int parentCapture)
                        : pos(p), H(h) {
 
   assert (!pos.in_check());
 
   // In ProbCut we consider only captures better than parent's move
-  captureThreshold = threshold;
+  captureThreshold = parentCapture;
   phasePtr = ProbCutTable;
 
   if (   ttm != MOVE_NONE
diff --git a/src/movepick.h b/src/movepick.h
index 5e4cf779..d0ced047 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -42,7 +42,7 @@ class MovePicker {
 public:
   MovePicker(const Position&, Move, Depth, const History&, SearchStack*, Value);
   MovePicker(const Position&, Move, Depth, const History&);
-  MovePicker(const Position&, Move, const History&, int threshold);
+  MovePicker(const Position&, Move, const History&, int parentCapture);
   Move get_next_move();
 
 private:
diff --git a/src/position.h b/src/position.h
index 1a714907..6c48b54c 100644
--- a/src/position.h
+++ b/src/position.h
@@ -213,6 +213,7 @@ public:
   // Static exchange evaluation
   int see(Move m) const;
   int see_sign(Move m) const;
+  static int see_value(PieceType pt);
 
   // Accessing hash keys
   Key get_key() const;
@@ -466,6 +467,10 @@ inline bool Position::square_is_weak(Square s, Color c) const {
   return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
 }
 
+inline int Position::see_value(PieceType pt) {
+  return seeValues[pt];
+}
+
 inline Key Position::get_key() const {
   return st->key;
 }
diff --git a/src/search.cpp b/src/search.cpp
index 6e440702..ec2b1c9c 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -903,8 +903,9 @@ namespace {
     }
 
     // Step 9. ProbCut (is omitted in PV nodes)
-    // If we have a good capture that raises the score well above beta and a reduced
-    // search confirms the score then we can (almost) safely prune the previous move.
+    // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
+    // and a reduced search returns a value much above beta, we can (almost) safely
+    // prune the previous move.
     if (   !PvNode
         &&  depth >= RazorDepth + ONE_PLY
         && !inCheck
@@ -917,7 +918,7 @@ namespace {
 
         assert(rdepth >= ONE_PLY);
 
-        MovePicker mp(pos, ttMove, H, Max(rbeta - refinedValue, VALUE_ZERO));
+        MovePicker mp(pos, ttMove, H, Position::see_value(pos.captured_piece_type()));
         pinned = pos.pinned_pieces(pos.side_to_move());
 
         while ((move = mp.get_next_move()) != MOVE_NONE)