From e67dfc5645e6c6abe23fba88733cf0bdbe20106f Mon Sep 17 00:00:00 2001
From: Calcitem <calcitem@outlook.com>
Date: Mon, 14 Jun 2021 11:42:37 +0800
Subject: [PATCH] evaluate: Do not attack too early when first 5 moves

If first 4 moves is placing at star point, move 5 temporarily use depth 1 search
in order to make sure white player do not attack and try to block black.
(For 9ms, star point is b4/d6/f4/d2)

This changed the white's moves.

For nine men's morris:

If first 4 moves is:
1. b4 d6
2. f4 d2
Next move, white will place at a4/c4/e4/g4,
now changed to place at d7/d5/d3/d1

If first 4 moves is:
1. b4 f4
2. d6 d2
Next move, white will place at b6, it is not wrong,
now changed to place at d4/g4/d3/d1, it is not wrong too.

Test result:

Play against Perfect Database:
400 games.
There is no significant change in the Draw rate.

Play 90 games against the pre-improved version:
White (New) Vs Black (Old)
White's win rate increased to 20%,  equivalent to Black's winning rate
Originally less than 10%.
---
 include/config.h |  2 +-
 src/evaluate.cpp | 14 +++++++++++---
 src/mills.cpp    | 25 +++++++++++++++++++++++++
 src/search.cpp   |  2 ++
 4 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/include/config.h b/include/config.h
index 6d6a09cb..a5d6a56e 100644
--- a/include/config.h
+++ b/include/config.h
@@ -25,7 +25,7 @@
 #pragma execution_character_set("utf-8")
 #endif
 
-//#define EVALUATE_MOBILITY
+#define EVALUATE_MOBILITY
 
 //#undef QT_GUI_LIB
 
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 2a88c308..97532850 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -56,6 +56,13 @@ Value Evaluation::value()
         break;
 
     case Phase::placing:
+#ifdef EVALUATE_MOBILITY
+        if (pos.piece_on_board_count(WHITE) + pos.piece_on_board_count(BLACK) <= 5) {
+            value += (Value)pos.get_mobility_diff();
+        }
+        //break;
+#endif  /* EVALUATE_MOBILITY */
+
         pieceInHandDiffCount = pos.piece_in_hand_count(WHITE) - pos.piece_in_hand_count(BLACK);
         value += VALUE_EACH_PIECE_INHAND * pieceInHandDiffCount;
 
@@ -77,12 +84,13 @@ Value Evaluation::value()
         break;
 
     case Phase::moving:
-        value = (pos.piece_on_board_count(WHITE) - pos.piece_on_board_count(BLACK)) * VALUE_EACH_PIECE_ONBOARD;
-
 #ifdef EVALUATE_MOBILITY
-        value += pos.get_mobility_diff() / 5;
+        //value += (Value)pos.get_mobility_diff();
+        //break;
 #endif  /* EVALUATE_MOBILITY */
 
+        value = (pos.piece_on_board_count(WHITE) - pos.piece_on_board_count(BLACK)) * VALUE_EACH_PIECE_ONBOARD;
+
         switch (pos.get_action()) {
         case Action::select:
         case Action::place:
diff --git a/src/mills.cpp b/src/mills.cpp
index b49589dc..7e971fc0 100644
--- a/src/mills.cpp
+++ b/src/mills.cpp
@@ -423,6 +423,25 @@ void move_priority_list_shuffle()
 #endif
 }
 
+bool is_star_squares_full(Position *pos)
+{
+    bool ret = false;
+    
+    if (rule.hasDiagonalLines) {
+        ret = (pos->get_board()[SQ_17] &&
+               pos->get_board()[SQ_19] &&
+               pos->get_board()[SQ_21] &&
+               pos->get_board()[SQ_23]);
+    } else {
+        ret = (pos->get_board()[SQ_16] &&
+               pos->get_board()[SQ_18] &&
+               pos->get_board()[SQ_20] &&
+               pos->get_board()[SQ_22]);
+    }
+
+    return ret;
+}
+
 Depth get_search_depth(const Position *pos)
 {
     Depth d = 0;
@@ -447,6 +466,12 @@ Depth get_search_depth(const Position *pos)
             const int index = rule.piecesCount * 2 - pos->count<IN_HAND>(WHITE) - pos->count<IN_HAND>(BLACK);
 
             d = placingDepthTable[index];
+
+            if (index == 4 &&
+                is_star_squares_full((Position *)pos)) {
+                d = 1;  // In order to use Mobility
+            }
+
             if (d == 0) {
                 return (Depth)gameOptions.getSkillLevel();
             } else {
diff --git a/src/search.cpp b/src/search.cpp
index cdf9f453..13d2c556 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -382,6 +382,8 @@ Value search(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth ori
             epsilon = 0;
         }
 
+        //epsilon += pos->piece_to_remove_count();
+
 #ifdef PVS_AI
         if (i == 0) {
             if (after != before) {