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From: Bonita Montero <Bonita.Montero@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: OT: Re: Sieve of Erastosthenes optimized to the max
Date: Mon, 2 Sep 2024 07:08:37 +0200
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Am 02.09.2024 um 05:40 schrieb Tim Rentsch:

> This is a brainless statement (and incidentally illustrates why I
> was motivated not to read postings from BM).  In fact no primes need
> be pre-calculated to determine whether any given number is prime.
> The point of using a sieve is the sieve method is much faster than
> not using one.  For example, suppose we want to determine all primes
> less than a trillion.  Taking the approach of pre-computing only
> those primes less than a million (the square root) and then testing
> numbers individually takes more than 100 times as many operations as
> using a sieve.  Furthermore the operations used are more expensive
> for the non-sieve approach - simply setting a bit in the case of a
> sieve, versus computing a remainder in the non-sieve case.


I don't wanted to say that each numbe is indivually sieved against all
primes up to the square root but a range. I do that myself to speed up
the computation.