[iagno] Allow even depth.

[Arnaud B. <arnaudb src gnome org>]

commit cd871695ac1942fe4ad81d9858f8d44329d15140
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Thu May 30 15:07:38 2019 +0200

    Allow even depth.
    
    And so use depth 3.

 src/computer-reversi.vala | 22 ++++++++++++++--------
 src/game.vala             | 33 +++++++++++++++++++++------------
 src/iagno.vala            |  2 +-
 3 files changed, 36 insertions(+), 21 deletions(-)
---
diff --git a/src/computer-reversi.vala b/src/computer-reversi.vala
index c7eb9ee..75bf8fb 100644
--- a/src/computer-reversi.vala
+++ b/src/computer-reversi.vala
@@ -81,6 +81,8 @@ private class ComputerReversiEasy : ComputerReversi
 
 private class ComputerReversiHard : ComputerReversi
 {
+    public bool even_depth { private get; protected construct; }
+
     construct
     {
         init_heuristic (size, out heuristic);
@@ -88,7 +90,7 @@ private class ComputerReversiHard : ComputerReversi
 
     internal ComputerReversiHard (Game game, uint8 initial_depth)
     {
-        Object (game: game, initial_depth: initial_depth);
+        Object (game: game, even_depth: initial_depth % 2 == 0, initial_depth: initial_depth);
     }
 
     /*\
@@ -116,10 +118,10 @@ private class ComputerReversiHard : ComputerReversi
 
     protected override int16 calculate_heuristic (GameStateStruct g)
     {
-        return eval_heuristic (g, ref heuristic);
+        return eval_heuristic (g, ref heuristic, even_depth);
     }
 
-    private static inline int16 eval_heuristic (GameStateStruct g, ref int16 [,] heuristic)
+    private static inline int16 eval_heuristic (GameStateStruct g, ref int16 [,] heuristic, bool even_depth)
     {
         uint8 size = g.size;
         int16 count = 0;
@@ -127,19 +129,23 @@ private class ComputerReversiHard : ComputerReversi
         {
             for (uint8 y = 0; y < size; y++)
             {
-                bool is_current_color = g.is_current_color (x, y);
+                bool is_move_color = (even_depth && !g.is_current_color (x, y)) || g.is_opponent_color (x, 
y);
 
                 // heuristic
                 int16 h = heuristic [x, y];
-                if (!is_current_color)
-                    h = -h;
-                count += h;
+                if (is_move_color)
+                    count -= h;
+                else
+                    count += h;
 
                 // around
                 int16 a = (int16) g.get_empty_neighbors (x, y);
                 if (a == 0) // completely surrounded
                     a = -7;
-                count += 4 * (is_current_color ? -a : a);
+                if (is_move_color)
+                    count += 4 * a;
+                else
+                    count -= 4 * a;
             }
         }
         return count;
diff --git a/src/game.vala b/src/game.vala
index 7a2e40e..ce58895 100644
--- a/src/game.vala
+++ b/src/game.vala
@@ -23,6 +23,7 @@
 private struct GameStateStruct
 {
     public Player   current_color;
+    public Player   opponent_color;
     public uint8    size;
 
     public uint8    n_current_tiles;
@@ -54,7 +55,8 @@ private struct GameStateStruct
      // requires (!game.is_complete)
     {
         // move color
-        current_color = Player.flip_color (game.current_color);
+        opponent_color = game.current_color;
+        current_color = Player.flip_color (opponent_color);
 
         // always given
         size = game.size;
@@ -81,8 +83,8 @@ private struct GameStateStruct
     internal GameStateStruct.copy_and_move (GameStateStruct game, PossibleMove move)
     {
         // move color
-        Player move_color = game.current_color;
-        current_color = Player.flip_color (move_color);
+        opponent_color = game.current_color;
+        current_color = Player.flip_color (opponent_color);
 
         // always given
         size = game.size;
@@ -90,15 +92,15 @@ private struct GameStateStruct
 
         // tiles grid
         tiles = game.tiles;
-        flip_tiles (ref tiles, move.x, move.y, move_color,  0, -1, move.n_tiles_n );
-        flip_tiles (ref tiles, move.x, move.y, move_color,  1, -1, move.n_tiles_ne);
-        flip_tiles (ref tiles, move.x, move.y, move_color,  1,  0, move.n_tiles_e );
-        flip_tiles (ref tiles, move.x, move.y, move_color,  1,  1, move.n_tiles_se);
-        flip_tiles (ref tiles, move.x, move.y, move_color,  0,  1, move.n_tiles_s );
-        flip_tiles (ref tiles, move.x, move.y, move_color, -1,  1, move.n_tiles_so);
-        flip_tiles (ref tiles, move.x, move.y, move_color, -1,  0, move.n_tiles_o );
-        flip_tiles (ref tiles, move.x, move.y, move_color, -1, -1, move.n_tiles_no);
-        tiles [move.x, move.y] = move_color;
+        flip_tiles (ref tiles, move.x, move.y, opponent_color,  0, -1, move.n_tiles_n );
+        flip_tiles (ref tiles, move.x, move.y, opponent_color,  1, -1, move.n_tiles_ne);
+        flip_tiles (ref tiles, move.x, move.y, opponent_color,  1,  0, move.n_tiles_e );
+        flip_tiles (ref tiles, move.x, move.y, opponent_color,  1,  1, move.n_tiles_se);
+        flip_tiles (ref tiles, move.x, move.y, opponent_color,  0,  1, move.n_tiles_s );
+        flip_tiles (ref tiles, move.x, move.y, opponent_color, -1,  1, move.n_tiles_so);
+        flip_tiles (ref tiles, move.x, move.y, opponent_color, -1,  0, move.n_tiles_o );
+        flip_tiles (ref tiles, move.x, move.y, opponent_color, -1, -1, move.n_tiles_no);
+        tiles [move.x, move.y] = opponent_color;
 
         // tiles counters
         n_current_tiles = game.n_opponent_tiles - move.n_tiles;
@@ -125,6 +127,7 @@ private struct GameStateStruct
     {
         // move color
         current_color = color;
+        opponent_color = Player.flip_color (color);
 
         // always given
         size = _size;
@@ -165,6 +168,12 @@ private struct GameStateStruct
         return tiles [x, y] == current_color;
     }
 
+    internal inline bool is_opponent_color (uint8 x, uint8 y)
+     // requires (is_valid_location_unsigned (x, y))
+    {
+        return tiles [x, y] == opponent_color;
+    }
+
     internal inline bool is_valid_location_signed (int8 x, int8 y)
     {
         return x >= 0 && x < size
diff --git a/src/iagno.vala b/src/iagno.vala
index e38f080..06e1de4 100644
--- a/src/iagno.vala
+++ b/src/iagno.vala
@@ -380,7 +380,7 @@ private class Iagno : Gtk.Application
             {
                 case 1 : computer = new ComputerReversiEasy (game);                break;
                 case 2 : computer = new ComputerReversiHard (game, /* depth */ 2); break;
-                case 3 : computer = new ComputerReversiHard (game, /* depth */ 4); break;
+                case 3 : computer = new ComputerReversiHard (game, /* depth */ 3); break;
                 default: assert_not_reached ();
             }
         }