There is a precomputation that 32 is the (rough) square root of 1000. There is no precomputation of primes. It is true that the code will not work beyond 1000

There is a precomputation that 32 is the (rough) square root of 1000. There is no precomputation of primes. It is true that the code will not work beyond 1000, unless you also add more selectors.