# include <math.h>
# include <mpi.h>
# include <stdio.h>
# include <stdlib.h>

int main ( int argc, char *argv[] )
{
  double e;
  double h;
  int i;
  int my_id;
  double my_q;
  int n;
  int p_num;
  double q;
  double x;

  MPI_Init ( &argc, &argv );
  MPI_Comm_rank ( MPI_COMM_WORLD, &my_id );
  MPI_Comm_size ( MPI_COMM_WORLD, &p_num );

  n = atoi ( argv[1] );

  h = 1.0 / ( double ) n / ( double ) ( p_num );
  x = ( double ) ( my_id ) / ( double ) ( p_num );

  my_q = 0.0;
  for ( i = 0; i < n; i++ )
  {
    my_q = my_q + h * 1.0 / ( x + 1.0 );
    x = x + h;
  }
  printf ( "  P:%d  MY_Q=%14.6g\n", my_id, my_q );

  MPI_Reduce ( &my_q, &q, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD );

  if ( my_id == 0 )
  {
    e = fabs ( q - log ( 2.0 ) );
    printf ( "  N=%6d  Q=%14.6g  E=%10.2e\n", n, q, e );
  }

  MPI_Finalize ( );

  return 0;
}