From 1a2768705ad389d1c4a234bf71354d05e56fcc1f Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 12 Sep 2010 14:02:33 +0100
Subject: [PATCH] Do not update king tables when we skip king safety

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---
 src/evaluate.cpp | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 72dc73a1..d791ed36 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -45,6 +45,11 @@ namespace {
     // Pointer to pawn hash table entry
     PawnInfo* pi;
 
+    // updateKingTables[color] is set to true if we have enough material
+    // to trigger the opponent's king safety calculation. When is false we
+    // skip the time consuming update of the king attackers tables.
+    bool updateKingTables[2];
+
     // attackedBy[color][piece type] is a bitboard representing all squares
     // attacked by a given color and piece type, attackedBy[color][0] contains
     // all squares attacked by the given color.
@@ -451,9 +456,13 @@ namespace {
     Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
     ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
     ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
-    b &= ei.attackedBy[Us][PAWN];
-    ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
-    ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
+    ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
+    if (ei.updateKingTables[Us])
+    {
+        b &= ei.attackedBy[Us][PAWN];
+        ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
+        ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
+    }
   }
 
 
@@ -515,7 +524,7 @@ namespace {
         ei.attackedBy[Us][Piece] |= b;
 
         // King attacks
-        if (b & ei.kingZone[Us])
+        if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
         {
             ei.kingAttackersCount[Us]++;
             ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
@@ -666,9 +675,8 @@ namespace {
 
     // King safety. This is quite complicated, and is almost certainly far
     // from optimally tuned.
-    if (   ei.kingAttackersCount[Them]  >= 2
-        && pos.non_pawn_material(Them)  >= QueenValueMidgame + RookValueMidgame
-        && pos.piece_count(Them, QUEEN) >= 1
+    if (   ei.updateKingTables[Them]
+        && ei.kingAttackersCount[Them] >= 2
         && ei.kingAdjacentZoneAttacksCount[Them])
     {
         // Find the attacked squares around the king which has no defenders
-- 
2.39.2