Large Model Sieve Program

The Sieve of Erosthostenes is a program that calculates
Prime numbers.  It is a standard benchmark used to determine
the relative speed of different computers or the efficiency
of the code generated for the same computer by different
compilers.

The sieve algorithm was developed in ancient Greece and is
one of a number of methods used to find prime numbers.
The sieve works by a process of elimination using an array
that starts with 2 and keeps all the numbers in position.
The process is:

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Starting after 2, eliminate all multiples of 2.

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
X   X   X   X   XX    XX    XX    XX    XX    XX    XX    XX

Starting after 3, eliminate all multiples of 3.

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
X   X   X   X X XX    XX    XX XX XX    XX    XX XX XX    XX

Starting after 5, eliminate all multiples of 5.

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
X   X   X   X X XX    XX    XX XX XX    XX    XX XX XX    XX XX

Continue until the next remaining number is greater than

the square root of the largest number in the original series.

In this case, the next number, 7, is greater than the square
root of 25, so the process stops.  The remaining numbers are all
prime!


