Porting optimized Sieve of Eratosthenes from Python to C++

Question

Some time ago I used the (blazing fast) primesieve in python that I found here: Fastest way to list all primes below N

To be precise, this implementation:

Answer 1

As an aside, you can "approximate" prime numbers. Call the approximate prime P. Here are a few formulas:

P = 2*k+1 // not divisible by 2

P = 6*k + {1, 5} // not divisible 2, 3

P = 30*k + {1, 7, 11, 13, 17, 19, 23, 29} // not divisble by 2, 3, 5

The properties of the set of numbers found by these formulas is that P may not be prime, however all primes are in the set P. I.e. if you only test numbers in the set P for prime, you won't miss any.

You can reformulate these formulas to:

P = X*k + {-i, -j, -k, k, j, i}

if that is more convenient for you.

Here is some code that uses this technique with a formula for P not divisible by 2, 3, 5, 7.

This link may represent the extent to which this technique can be practically leveraged.