From a389dd0562699e36c196d69c578a1f1c373a12ab Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Thu, 18 Aug 2022 09:58:52 +0300
Subject: feat: use board coverage in metrics

---
 src/main.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

(limited to 'src/main.c')

diff --git a/src/main.c b/src/main.c
index b18c7ea..edb553b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -261,6 +261,33 @@ int compute_material_advantage(int* board, int color) {
   return counter;
 }
 
+int compute_coverage(int* board, int color) {
+  int counter = 0;
+  for (int rank = 7; rank >= 0; rank--) {
+    for (int file = 0; file < 8; file++) {
+      int index = rank * 16 + file;
+      int piece = board[index];
+      if (piece != EMPTY && (piece % 2) == color) {
+        for (int rank_destination = 7; rank_destination >= 0; rank_destination--) {
+          for (int file_destination = 0; file_destination < 8; file_destination++) {
+            int index_destination = rank_destination * 16 + file_destination;
+            int move[2] = { index, index_destination };
+            if (validate_move(move, color, board) >= 0) {
+              counter++;
+            }
+          }
+        }
+      }
+    }
+  }
+  return counter;
+}
+
+int compute_score(int* board) {
+  int coverage_score = compute_coverage(board, WHITE) - compute_coverage(board, BLACK);
+  return compute_material_advantage(board, WHITE) + coverage_score;
+}
+
 // Alpha-beta pruning
 // Value here is white material advantage over black
 // Alpha is the best value for maximizer (white)
@@ -294,7 +321,7 @@ int find_best_move(int* board, int color, int depth, int alpha, int beta) {
 
               int value = depth < MAX_DEPTH
                 ? find_best_move(fake_board, 1 - color, depth + 1, alpha, beta)
-                : compute_material_advantage(fake_board, 0); // Always for maximizer (white)
+                : compute_score(fake_board);
 
               if (is_maximizer) {
                 if (value > best_value) {
@@ -341,7 +368,7 @@ int main() {
   int color = 0;
 
   while (1) {
-    printf("Current board advantage is %i\n", compute_material_advantage(board, 0));
+    printf("Current score is %i\n", compute_score(board));
     find_best_move(board, color, 0, -INFINITY, +INFINITY);
     printf("Enter a move for %s:\n", COLORS[color]);
     input_move(move);
-- 
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