# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <ctime>

using namespace std;

int main ( int argc, char *argv[] );
int prime_part ( int id, int p, int n );

int main ( int argc, char *argv[] )

//****************************************************************************80
//
//  Purpose:
//
//    PRIME counts the prime numbers between 2 and N.
//
//  Discussion:
//
//    We divide the calculation up into P parts.
//
//    Part 0   checks 2+0,   2+P+0,   2+2*P+0, ...
//    Part 2   checks 2+1,   2+P+1,   2+2*P+1, ...
//    Part P-1 checks 2+P-1, 2+2*P-1, 2+3*P-1, ...
//
//    Right now, the outer loop executes all P parts.
//    But it would be simple to make an MPI version, in which the
//    program with identifier ID only executes part ID.
//
//    Modify this program so that it runs under MPI.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    07 September 2013
//
//  Author:
//
//    John Burkardt
//
{
  int id;
  int n = 100000;
  int p;
  int total;
  int total_part;

  cout << "\n";
  cout << "PRIME\n";
  cout << "  C++ version\n";

  p = 4;

  total = 0;
  for ( id = 0; id < p; id++ )
  {
    total_part = prime_part ( id, p, n );
    total = total + total_part;
  }
  cout << "\n";
  cout << "  Between 2 and " << n << " there are " << total << " primes.\n";

  return 0;
}
int prime_part ( int id, int p, int n )
{
  int i;
  int j;
  bool prime;
  int total_part;

  total_part = 0;

  for ( i = 2 + id; i <= n; i = i + p )
  {
    prime = true;

    for ( j = 2; j < i; j++ )
    {
      if ( i % j == 0 )
      {
        prime = false;
        break;
      }
    }
    if ( prime )
    {
      total_part = total_part + 1;
    }
  }

  return total_part;
}