How to create the most compact mapping n → isprime(n) up to a limit N?

Question

Naturally, for bool isprime(number) there would be a data structure I could query.
I define the best algorithm, to be the algorithm that pr

Answer 1

There are many ways to do the primality test.

There isn't really a data structure for you to query. If you have lots of numbers to test, you should probably run a probabilistic test since those are faster, and then follow it up with a deterministic test to make sure the number is prime.

You should know that the math behind the fastest algorithms is not for the faint of heart.