From 4361f34949429f36068fbe0ecb1a7ea1f6f97129 Mon Sep 17 00:00:00 2001
From: Cab <cab1.01.kq@gmail.com>
Date: Sat, 10 Feb 2024 10:09:19 +0300
Subject: [PATCH] disable pawn check if no promotion available

---
 src/position.cpp | 38 ++++++++++++++++++++++++++++++++++++--
 src/position.h   |  2 ++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/src/position.cpp b/src/position.cpp
index 50516883f..77a3f83dd 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -530,6 +530,7 @@ Position& Position::set(const Variant* v, const string& fenStr, bool isChess960,
   chess960 = isChess960 || v->chess960;
   tsumeMode = Options["TsumeMode"];
   thisThread = th;
+  updatePawnCheckZone();
   set_state(st);
 
   assert(pos_is_ok());
@@ -936,7 +937,7 @@ Bitboard Position::attackers_to(Square s, Bitboard occupied, Color c, Bitboard j
   // Use a faster version for variants with moderate rule variations
   if (var->fastAttacks)
   {
-      return  (pawn_attacks_bb(~c, s)          & pieces(c, PAWN))
+      return  (pawn_attacks_bb(~c, s)          & pieces(c, PAWN) & ~pawnCannotCheckZone[c])
             | (attacks_bb<KNIGHT>(s)           & pieces(c, KNIGHT, ARCHBISHOP, CHANCELLOR))
             | (attacks_bb<  ROOK>(s, occupied) & pieces(c, ROOK, QUEEN, CHANCELLOR))
             | (attacks_bb<BISHOP>(s, occupied) & pieces(c, BISHOP, QUEEN, ARCHBISHOP))
@@ -2111,11 +2112,12 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
       k ^= Zobrist::wall[gating_square(m)];
   }
 
+  updatePawnCheckZone();
   // Update the key with the final value
   st->key = k;
   // Calculate checkers bitboard (if move gives check)
   st->checkersBB = givesCheck ? attackers_to(square<KING>(them), us) & pieces(us) : Bitboard(0);
-  assert(givesCheck == bool(st->checkersBB));
+  assert(givesCheck == bool(st->checkersBB) || givesCheck && var->prisonPawnPromotion);
 
   sideToMove = ~sideToMove;
 
@@ -2954,6 +2956,13 @@ bool Position::is_immediate_game_end(Value& result, int ply) const {
           return true;
       }
   }
+  if (var->prisonPawnPromotion &&
+      (pawn_attacks_bb(~sideToMove, square<KING>(~sideToMove))
+       & pieces(sideToMove, PAWN)
+       & ~pawnCannotCheckZone[sideToMove]) ){
+      result = mate_in(ply);
+      return true;
+  }
 
   return false;
 }
@@ -3252,6 +3261,31 @@ void Position::flip() {
   assert(pos_is_ok());
 }
 
+void Position::updatePawnCheckZone() {
+    if (!var->prisonPawnPromotion) {
+        pawnCannotCheckZone[WHITE] = Bitboard(0);
+        pawnCannotCheckZone[BLACK] = Bitboard(0);
+        return;
+    }
+    for (Color color : { BLACK, WHITE }) {
+        if (count<KING>(~color) == 0) {
+            pawnCannotCheckZone[color] = Bitboard(0);
+        } else {
+            bool canPromotion = false;
+            for (PieceSet prom = promotion_piece_types(color) & rescueFor(PAWN); prom; ) {
+                PieceType pt = pop_lsb(prom);
+                if (count_in_prison(~color, pt) > 0) {
+                    canPromotion = true;
+                    break;
+                }
+            }
+            Bitboard pz = promotion_zone(color);
+            pawnCannotCheckZone[color] = canPromotion
+                    ? Bitboard(0)
+                    : color == WHITE ? shift(SOUTH, pz) : shift(NORTH, pz);
+        }
+    }
+}
 
 /// Position::pos_is_ok() performs some consistency checks for the
 /// position object and raises an asserts if something wrong is detected.
diff --git a/src/position.h b/src/position.h
index 792d26afd..dd32a0c22 100644
--- a/src/position.h
+++ b/src/position.h
@@ -372,12 +372,14 @@ class Position {
   bool chess960;
   int pieceCountInHand[COLOR_NB][PIECE_TYPE_NB];
   int pieceCountInPrison[COLOR_NB][PIECE_TYPE_NB];
+  Bitboard pawnCannotCheckZone[COLOR_NB];
   int virtualPieces;
   Bitboard promotedPieces;
   void add_to_hand(Piece pc);
   int add_to_prison(Piece pc);
   void remove_from_hand(Piece pc);
   int remove_from_prison(Piece pc);
+  void updatePawnCheckZone();
   void drop_piece(Piece pc_hand, Piece pc_drop, Square s, PieceType exchange);
   void undrop_piece(Piece pc_hand, Square s, PieceType exchange);
   Bitboard find_drop_region(Direction dir, Square s, Bitboard occupied) const;