From a72faadd25af5bf7d80aab9d9adf48e765bed630 Mon Sep 17 00:00:00 2001
From: Vincent Ollivier <contact@vincentollivier.com>
Date: Thu, 14 Jun 2012 19:52:12 +0200
Subject: [PATCH] Refactor killer moves

---
 src/game.cpp   |  2 +-
 src/game.h     | 13 +++++++++----
 src/search.cpp | 15 +++++++--------
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/src/game.cpp b/src/game.cpp
index 4f1f130..703a236 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -109,7 +109,7 @@ void Game::del_position()
 /*
  * Killer move setter for the Killer Heuristic in move ordering.
  */
-void Game::set_killer_move(int depth, Move move)
+void Game::set_killer(const Move move, const int depth)
 {
     if (move != killer_moves[depth][0]) {
         killer_moves[depth][1] = killer_moves[depth][0];
diff --git a/src/game.h b/src/game.h
index ab5b667..3a18ecd 100644
--- a/src/game.h
+++ b/src/game.h
@@ -84,11 +84,16 @@ class Game
 
         // Killer Moves
         void clear_killers();
-        Move killer_move(int depth, int index) {
+        /*
+        Move killer(int depth, int index) {
             return killer_moves[depth][index];
-        }
-        void set_killer_move(int depth, Move move);
-        bool is_killer_move(int depth, Move move) {
+        };
+        */
+        Move (&killers(const int depth))[MAX_KILLERS] {
+            return killer_moves[depth];
+        };
+        void set_killer(const Move move, const int depth);
+        bool is_killer(const Move move, const int depth) {
             return (move == killer_moves[depth][0] ||
                     move == killer_moves[depth][1]);
         };
diff --git a/src/search.cpp b/src/search.cpp
index 9ebf51f..5606a87 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -203,10 +203,9 @@ int Game::search(int alpha, int beta, int depth, const int ply)
     // Killer moves need pseudo legality checking before we can use them,
     // but they can cause a cut-off and dispense to generate quiet moves
     // so it's worth it.
-    for (int i = 0; i < MAX_KILLERS; ++i) {
-        Move killer = killer_move(depth, i);
-        if (is_legal(killer)) {
-            moves.add(killer, KILLERS);
+    for (const Move &killer_move : killers(depth)) {
+        if (is_legal(killer_move)) {
+            moves.add(killer_move, KILLERS);
         }
     }
 
@@ -233,7 +232,7 @@ int Game::search(int alpha, int beta, int depth, const int ply)
                 if (best_score >= beta) { // Beta cut-off
                     // Update killer moves
                     if (!move.is_capture()) {
-                        set_killer_move(depth, move);
+                        set_killer(move, depth);
                     }
 
                     best_move = move;
@@ -250,7 +249,7 @@ int Game::search(int alpha, int beta, int depth, const int ply)
             const bool fp_allowed =
                 !is_in_check &&
                 !is_giving_check &&
-                !is_killer_move(depth, move) &&
+                !is_killer(move, depth) &&
                 !is_dangerous(move) &&
                 !move.is_castle() &&
                 legal_move_found &&
@@ -274,7 +273,7 @@ int Game::search(int alpha, int beta, int depth, const int ply)
             const bool lmr_allowed =
                 !is_in_check &&
                 !is_giving_check &&
-                !is_killer_move(depth, move) &&
+                !is_killer(move, depth) &&
                 !move.is_capture() &&
                 !move.is_promotion();
 
@@ -301,7 +300,7 @@ int Game::search(int alpha, int beta, int depth, const int ply)
                 best_move = move;
                 if (score >= beta) { // Sufficient to cause a cut-off?
                     if (!move.is_capture()) {
-                        set_killer_move(depth, move); // Update killer moves
+                        set_killer(move, depth); // Update killer moves
                     }
 
                     goto transposition;
-- 
2.11.4.GIT