# include <stdlib.h>
# include <stdio.h>
# include <time.h>

# include "mpi.h"

int main ( int argc, char *argv[] );
int search ( int a, int b, int c, int id, int p );
int f ( int i );

/******************************************************************************/

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

/******************************************************************************/
/*
  Purpose:

    MAIN is the main program for SEARCH_MPI.

  Licensing:

    This code is distributed under the GNU LGPL license.

  Modified:

    01 November 2012

  Author:

    John Burkardt
*/
{
  int a;
  int b;
  int c;
  int fj;
  int i4_huge = 2147483647;
  int id;
  int j;
  int p;
  double wtime;
/*
  Initialize MPI.
*/
  MPI_Init ( &argc, &argv );
/*
  Get this processor's ID.
*/
  MPI_Comm_rank ( MPI_COMM_WORLD, &id );
/*
  Get the number of processes.
*/
  MPI_Comm_size ( MPI_COMM_WORLD, &p );

  a = 1;
  b = i4_huge;
  c = 45;

  if ( id == 0 )
  {
    printf ( "SEARCH_MPI:\n" );
    printf ( "  C/MPI version\n" );
    printf ( "  Search the integers from A to B\n" );
    printf ( "  for a value J such that F(J) = C.\n" );
    printf ( "\n" );
    printf ( "  A           = %d\n", a );
    printf ( "  B           = %d\n", b );
    printf ( "  C           = %d\n", c );
  }

  wtime = MPI_Wtime ( );

  j = search ( a, b, c, id, p );

  wtime = MPI_Wtime ( ) - wtime;

  if ( j != -1 )
  {
    printf ( "\n" );
    printf ( "  Process %d found     J = %d\n", id, j );
    printf ( "  Verify F(J) = %d\n", f ( j ) );
  }

  if ( id == 0 )
  {
    printf ( "  Elapsed wallclock time is %g\n", wtime );
  }
/*
  Terminate MPI.
*/
  MPI_Finalize ( );
/*
  Terminate.
*/
  if ( id == 0 )
  {
    printf ( "\n" );
    printf ( "SEARCH_MPI:\n" );
    printf ( "  Normal end of execution.\n" );
  }

  return 0;
}
/******************************************************************************/

int search ( int a, int b, int c, int id, int p )

/******************************************************************************/
/*
  Purpose:

    SEARCH searches integers in [A,B] for a J so that F(J) = C.

  Licensing:

    This code is distributed under the GNU LGPL license.

  Modified:

    01 November 2012

  Author:

    John Burkardt

  Parameters:

    Input, int A, B, the search range.

    Input, int C, the desired function value.

    Input, int ID, the process ID.

    Input, int P, the number of processes.

    Output, int SEARCH, the computed solution, or -1
    if no solution was found.
*/
{
  int fi;
  int i;
  int j;

  j = -1;
/*
  i = i + p can take us "over top" so that i becomes negative!
  So we have to be more careful here!
*/
  for ( i = a + id; 0 < i && i <= b; i = i + p )
  {
    fi = f ( i );

    if ( fi == c )
    {
      j = i;
      break;
    }
  }

  return j;
}
/******************************************************************************/

int f ( int i )

/******************************************************************************/
/*
  Purpose:

    F is the function we are analyzing.

  Licensing:

    This code is distributed under the GNU LGPL license.

  Modified:

    22 October 2012

  Author:

    John Burkardt

  Parameters:

    Input, int I, the argument.

    Input, int F, the value.
*/
{
  int i4_huge = 2147483647;
  int j;
  int k;
  int value;

  value = i;

  for ( j = 1; j <= 5; j++ )
  {
    k = value / 127773;

    value = 16807 * ( value - k * 127773 ) - k * 2836;

    if ( value <= 0 )
    {
      value = value + i4_huge;
    }
  }

  return value;
}