From 4c74671e9d2cc4c5de6f3069fe66b310ab506eda Mon Sep 17 00:00:00 2001
From: Vincent Ollivier <contact@vincentollivier.com>
Date: Fri, 6 Apr 2012 07:48:07 +0200
Subject: [PATCH] Add Game::is_dangerous() for Futility Pruning

---
 src/game.h     |  1 +
 src/search.cpp | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/game.h b/src/game.h
index 8336017..72e106b 100644
--- a/src/game.h
+++ b/src/game.h
@@ -67,6 +67,7 @@ class Game
         void make_move(Move m);
         void undo_move(Move m);
         bool is_legal(Move m);
+        bool is_dangerous(Move m);
 
         // Search
         unsigned long long int perft(unsigned int depth);
diff --git a/src/search.cpp b/src/search.cpp
index 8283d3d..3f37a10 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -24,6 +24,26 @@
 #include "search.h"
 #include "eval.h"
 
+inline bool Game::is_dangerous(Move m)
+{
+    // current_position() is used assuming
+    // that the move as already been made.
+
+    /*
+    if (board.get_piece(m.get_dest()).get_type() == PAWN) {
+        const Color c = !current_position().get_turn_color();
+        if (m.get_dest_rank() + RANK_6 * c == RANK_7) return true;
+    }
+    if (m.is_capture()) {
+        const Piece capture = current_position().get_capture();
+        if (capture.get_type() != PAWN) return true;
+    }
+    return m.is_promotion();
+    */
+
+    return m.is_capture() || m.is_promotion();
+}
+
 unsigned long long int Game::perft(unsigned int depth)
 {
     if (depth == 0) return 1;
@@ -231,8 +251,7 @@ int Game::search(int alpha, int beta, int depth, const int ply)
                 !is_in_check &&
                 !is_giving_check &&
                 !is_killer_move(depth, move) &&
-                !move.is_capture() &&
-                !move.is_promotion();
+                !is_dangerous(move);
 
             if (fp_allowed && depth <= FUTILITY_DEPTH) {
                 // Using an array of margins is an idea from Crafty
-- 
2.11.4.GIT