From 5db45a760a8eebf5de2efd5d784c75ddf93f0640 Mon Sep 17 00:00:00 2001
From: Bruno Raoult <braoult@gmail.com>
Date: Wed, 15 May 2024 18:36:30 +0200
Subject: [PATCH] fen: calc pos hash, hash: fix zobrist_init, add
 zobrist_verify

---
 src/fen.c  |  4 +++-
 src/hash.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 src/hash.h |  1 +
 3 files changed, 60 insertions(+), 3 deletions(-)

diff --git a/src/fen.c b/src/fen.c
index 2818000..6f8d2c1 100644
--- a/src/fen.c
+++ b/src/fen.c
@@ -250,8 +250,10 @@ end:
     }
     if (fen_check(&tmppos) < 0)
         return NULL;
+    tmppos.key = zobrist_calc(&tmppos);
     if (!pos)
-        pos = pos_dup(&tmppos);
+        pos = pos_new();
+    pos_copy(&tmppos, pos);
     //puts("prout 1");
     //pos_print_raw(&tmppos, 1);
     //puts("prout 2");
diff --git a/src/hash.c b/src/hash.c
index befa61c..b8eb00d 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -51,6 +51,7 @@ void zobrist_init(void)
 
 /**
  * zobrist_calc() - calculate a position zobrist hash.
+ * @pos: &position
  *
  * Normally, Zobrist keys are incrementally calculated when doing or
  * undoing a move.
@@ -58,6 +59,7 @@ void zobrist_init(void)
  * - When starting a new position
  * - To verify incremental Zobrist calculation is correct
  *
+ * @return: @pos Zobrist key
  */
 key_t zobrist_calc(pos_t *pos)
 {
@@ -76,12 +78,64 @@ key_t zobrist_calc(pos_t *pos)
             }
         }
     }
-    key ^= pos->castle;
-    key ^= EP_ZOBRIST_IDX(pos->en_passant);
+    key ^= zobrist_castling[pos->castle];
+    key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
 
     return key;
 }
 
+/**
+ * zobrist_verify() - verify current position Zobrist key.
+ * @pos: &position
+ *
+ * Verify that position Zobrist key matches a full Zobrist calculation.
+ * This function cannot be called if DEBUG_HASH is not set.
+ *
+ * @return: True if Zobrist key is OK.
+ */
+#ifdef DEBUG_HASH
+bool zobrist_verify(pos_t *pos)
+{
+    key_t diff, key = zobrist_calc(pos);
+
+    if (pos->key == key)
+        return true;
+
+    printf("key verify: cur=%#lx != %#lx\n", pos->key, key);
+
+    /* try to find-out the key in different zobrist tables */
+    diff = pos->key ^ key;
+
+    for (color_t c = WHITE; c <= BLACK; ++c) {
+        for (piece_type_t p = PAWN; p <= KING; ++p)
+            for (square_t sq = A1; sq <= H8; ++sq)
+                if (diff == zobrist_pieces[MAKE_PIECE(p, c)][sq]) {
+                    warn(true, "zobrist difference is piece:[%s][%s]\n",
+                         piece_to_fen(MAKE_PIECE(p, c)), sq_to_string(sq));
+                    goto end;
+                }
+    }
+    for (castle_rights_t c = CASTLE_NONE; c <= CASTLE_ALL; ++c)
+        if (diff == zobrist_castling[c]) {
+            warn(true, "zobrist difference is castling:[%d]\n", c);
+            goto end;
+        }
+
+    for (file_t f = FILE_A; f <= FILE_H; ++f)
+        if (diff == zobrist_ep[f]) {
+            warn(true, "zobrist difference is ep:[%d]\n", f);
+            goto end;
+        }
+    if (diff == zobrist_turn) {
+        warn(true, "zobrist difference is turn\n");
+        goto end;
+    }
+    warn(true, "zobrist diff %lx is unknown\n", diff);
+end:
+    return false;
+}
+#endif
+
 /**
  * hash_create() - hashtable creation.
  * @sizemb: s32 size of hash table in Mb
diff --git a/src/hash.h b/src/hash.h
index 76cc880..e639250 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -90,6 +90,7 @@ extern hasht_t hash_tt;                           /* main transposition table */
 
 void zobrist_init(void);
 key_t zobrist_calc(pos_t *pos);
+bool zobrist_verify(pos_t *pos);
 
 int hash_create(int Mb);
 void hash_clear(void);