From d26b99ec280e5e0971c4abc9cfc85445f40fc4d5 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Wed, 31 Aug 2022 02:38:44 +0300
Subject: feat: implement initial zobrist hashing

---
 src/config.h |  1 +
 src/main.c   | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/config.h b/src/config.h
index 9273f0e..4031d91 100644
--- a/src/config.h
+++ b/src/config.h
@@ -4,3 +4,4 @@
 #define MAX_AVAILABLE_MOVES 64 * 64
 #define INFINITY 1000000
 #define PLAYER WHITE
+#define MAX_ZOBRIST_SEEDS 1500
diff --git a/src/main.c b/src/main.c
index 5a66201..f1eb6a3 100644
--- a/src/main.c
+++ b/src/main.c
@@ -12,6 +12,28 @@
 #define MAX(x, y) (((x) > (y)) ? (x) : (y))
 #define MIN(x, y) (((x) < (y)) ? (x) : (y))
 
+void generate_zobrist_seed(int* seed) {
+  for (int i = 0; i < 781; i++) {
+    seed[i] = rand();
+  }
+}
+
+int zobrist_hash(int* seed, int* board, int color_to_move) {
+  int result = seed[color_to_move];
+  for (int rank = 7; rank >= 0; rank--) {
+    for (int file = 0; file < 8; file++) {
+      int position = rank * 16 + file;
+      int piece = board[position];
+      if (piece != EMPTY) {
+        // Unique index of this piece on this position
+        int zobrist_index = (piece * 128) + position;
+        result ^= seed[zobrist_index];
+      }
+    }
+  }
+  return result;
+}
+
 
 void print_board(int board[128]) {
   for (int rank = 7; rank >= 0; rank--) {
@@ -500,7 +522,13 @@ int main() {
   Move move;
   int color = WHITE;
 
+  int zobrist_seed[MAX_ZOBRIST_SEEDS];
+  generate_zobrist_seed(zobrist_seed);
+
   while (1) {
+    int hash = zobrist_hash(zobrist_seed, board, color);
+    printf("Zobrist hash: %i\n", hash);
+
     if (color == PLAYER) {
       printf("Enter a move for %s:\n", COLORS[color]);
       move = input_move();
-- 
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