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Fix game cycle detection #431

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Merged
TheRealGioviok merged 1 commit into from
Oct 10, 2026
Merged

Fix game cycle detection #431

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5 changes: 3 additions & 2 deletions src/repetition_info.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include "position.hpp"
#include "rays.hpp"
#include "util/types.hpp"
#include "zobrist.hpp"
#include <unordered_set>

namespace Clockwork {
Expand Down Expand Up @@ -73,12 +74,12 @@ bool RepetitionInfo::has_game_cycle(const Position& pos, usize ply) {
Bitboard occ = pos.board().get_occupied_bitboard();
HashKey original_key = pos.get_hash_key();

HashKey other = ~(original_key ^ old_key(2));
HashKey other = original_key ^ old_key(2) ^ Zobrist::side_key;

for (usize i = 3; i <= end; i += 2) {
HashKey curr_key = old_key(i + 1);

other ^= ~(curr_key ^ old_key(i));
other ^= curr_key ^ old_key(i) ^ Zobrist::side_key;
if (other != 0) {
continue;
}
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