From 4064ee540649cb46ad4cc4a6080bd4ef41314cb9 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 21 Jul 2013 01:45:47 +0200
Subject: [PATCH] Simplify captures ordering

A big simplification and removing of useless code.

Finished at 50% both at short TC (with SPRT) than
at long TC at fixed number of games:
ELO: -0.14 +-3.4 (95%) LOS: 46.8%
Total: 15206 W: 2836 L: 2842 D: 9528

bench: 5059948
---
 src/movepick.cpp | 19 +++----------------
 src/movepick.h   |  2 +-
 src/search.cpp   |  2 +-
 3 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 8445260b..4f2fa01e 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -70,12 +70,11 @@ namespace {
 /// search captures, promotions and some checks) and about how important good
 /// move ordering is at the current node.
 
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h, Move* cm,
-                       Search::Stack* s, Value beta) : pos(p), history(h), depth(d) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
+                       Move* cm, Search::Stack* s) : pos(p), history(h), depth(d) {
 
   assert(d > DEPTH_ZERO);
 
-  captureThreshold = 0;
   cur = end = moves;
   endBadCaptures = moves + MAX_MOVES - 1;
   countermoves = cm;
@@ -85,18 +84,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats&
       stage = EVASION;
 
   else
-  {
       stage = MAIN_SEARCH;
 
-      // Consider sligtly negative captures as good if at low depth and far from beta
-      if (ss->staticEval < beta - PawnValueMg && d < 3 * ONE_PLY)
-          captureThreshold = -PawnValueMg;
-
-      // Consider negative captures as good if still enough to reach beta
-      else if (ss->staticEval > beta)
-          captureThreshold = beta - ss->staticEval;
-  }
-
   ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
   end += (ttMove != MOVE_NONE);
 }
@@ -317,9 +306,7 @@ Move MovePicker::next_move<false>() {
           move = pick_best(cur++, end)->move;
           if (move != ttMove)
           {
-              assert(captureThreshold <= 0); // Otherwise we cannot use see_sign()
-
-              if (pos.see_sign(move) >= captureThreshold)
+              if (pos.see_sign(move) >= 0)
                   return move;
 
               // Losing capture, move it to the tail of the array
diff --git a/src/movepick.h b/src/movepick.h
index 363b1a1b..572025f2 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -86,7 +86,7 @@ class MovePicker {
 public:
   MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
   MovePicker(const Position&, Move, const HistoryStats&, PieceType);
-  MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Search::Stack*, Value);
+  MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Search::Stack*);
 
   template<bool SpNode> Move next_move();
 
diff --git a/src/search.cpp b/src/search.cpp
index 3985ad30..c6bc8e37 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -762,7 +762,7 @@ moves_loop: // When in check and at SpNode search starts from here
     Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
                             Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
 
-    MovePicker mp(pos, ttMove, depth, History, countermoves, ss, PvNode ? -VALUE_INFINITE : beta);
+    MovePicker mp(pos, ttMove, depth, History, countermoves, ss);
     CheckInfo ci(pos);
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
     singularExtensionNode =   !RootNode
-- 
2.39.2