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The first-place Rust program uses this very simple low-security hash function:

    impl Hasher for NaiveHasher {
        fn write_u64(&mut self, i: u64) {
            self.0 = i ^ i >> 7;
        }
    }

The second-place C program uses the exact same hash function as the Rust program, except it also truncates the result to 32 bits:

    #define CUSTOM_HASH_FUNCTION(key) (khint32_t)((key) ^ (key)>>7)

The third-place C++ program uses the identity function as its hash function:

    struct hash{
        uint64_t operator()(const T& t)const{ return t.data; }
    };

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