+void dbg_hit_on(bool b);
+void dbg_hit_on(bool c, bool b);
+void dbg_mean_of(int v);
+void dbg_print();
+
+typedef std::chrono::milliseconds::rep TimePoint; // A value in milliseconds
+
+static_assert(sizeof(TimePoint) == sizeof(int64_t), "TimePoint should be 64 bits");
+
+inline TimePoint now() {
+ return std::chrono::duration_cast<std::chrono::milliseconds>
+ (std::chrono::steady_clock::now().time_since_epoch()).count();
+}
+
+template<class Entry, int Size>
+struct HashTable {
+ Entry* operator[](Key key) { return &table[(uint32_t)key & (Size - 1)]; }
+
+private:
+ std::vector<Entry> table = std::vector<Entry>(Size);
+};
+
+
+enum SyncCout { IO_LOCK, IO_UNLOCK };
+std::ostream& operator<<(std::ostream&, SyncCout);
+
+#define sync_cout std::cout << IO_LOCK
+#define sync_endl std::endl << IO_UNLOCK
+
+
+/// xorshift64star Pseudo-Random Number Generator
+/// This class is based on original code written and dedicated
+/// to the public domain by Sebastiano Vigna (2014).
+/// It has the following characteristics:
+///
+/// - Outputs 64-bit numbers
+/// - Passes Dieharder and SmallCrush test batteries
+/// - Does not require warm-up, no zeroland to escape
+/// - Internal state is a single 64-bit integer
+/// - Period is 2^64 - 1
+/// - Speed: 1.60 ns/call (Core i7 @3.40GHz)
+///
+/// For further analysis see
+/// <http://vigna.di.unimi.it/ftp/papers/xorshift.pdf>