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

# include "ppc_gauss_quad.h"

int main ( );
void demo1 ( );
void demo2 ( );
double f ( double x );
void timestamp ( );

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

int main ( ) 

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

    ppc_gauss_quad_test() tests ppc_gauss_quad().

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    19 May 2024

  Author:

    John Burkardt.

  Reference:

    Rouben Rostamian,
    Programming Projects in C 
    for Students of Engineering, Science, and Mathematics,
    SIAM, 2014,
    ISBN: 978-1-611973-49-5
*/
{
  timestamp ( );

  printf ( "\n" );
  printf ( "ppc_gauss_quad_test():\n" );
  printf ( "  C version\n" );
  printf ( "  Test ppc_gauss_quad():\n" );

  demo1 ( );
  demo2 ( );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "ppc_gauss_quad_test():\n" );
  printf ( "  Normal end of execution.\n" );

  timestamp ( );

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

void demo1 ( ) 

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

    demo1() retrieves and prints the points and weights.

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    19 May 2024

  Author:

    John Burkardt.

  Reference:

    Rouben Rostamian,
    Programming Projects in C 
    for Students of Engineering, Science, and Mathematics,
    SIAM, 2014,
    ISBN: 978-1-611973-49-5
*/
{
  struct Gauss_qdat *gqdat;
  int i;
  int n;

  printf ( "\n" );
  printf ( "demo1():\n" );
  printf ( "  Request a 10 point quadrature rule.\n" );
  printf ( "  Print the points and weights.\n" );

  n = 10;
  gqdat = gauss_qdat ( &n );

  printf ( "\n" );
  printf ( "      Weight      Point\n" );
  printf ( "\n" );
  for ( i = 0; i < n; i++ )
  {
    printf ( "  %10.4f  %10.4f\n", gqdat[i].w, gqdat[i].p );
  }

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

void demo2 ( ) 

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

    demo2() estimates an integral over [-1,+1].

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    19 May 2024

  Author:

    John Burkardt.

  Reference:

    Rouben Rostamian,
    Programming Projects in C 
    for Students of Engineering, Science, and Mathematics,
    SIAM, 2014,
    ISBN: 978-1-611973-49-5
*/
{
  double e;
  double exact = 1.9922524079504000171;
  struct Gauss_qdat *gqdat;
  int i;
  int n;
  double s;

  printf ( "\n" );
  printf ( "demo2():\n" );
  printf ( "  Estimate an integral with a sequence of rules.\n" );

  printf ( "\n" );
  printf ( "  N           Estimate       Error\n" );
  printf ( "\n" );

  for ( n = 1; n <= 10; n++ )
  {
    gqdat = gauss_qdat ( &n );
    s = 0.0;
    for ( i = 0; i < n; i++ )
    {
      s = s + gqdat[i].w * f ( gqdat[i].p );
    }
    e = fabs ( s - exact );
    printf ( "  %2d  %16.8f  %16.8f\n", n, s, e );
  }

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

double f ( double x )

/******************************************************************************/
{
  double value;
  value = 1.0 / ( pow ( x, 6 ) + 0.9 );
  return value;
}
/******************************************************************************/

void timestamp ( )

/******************************************************************************/
/*
  Purpose:
 
    timestamp() prints the current YMDHMS date as a time stamp.

  Example:

    17 June 2014 09:45:54 AM

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    01 May 2021

  Author:

    John Burkardt
*/
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct tm *tm;
  time_t now;

  now = time ( NULL );
  tm = localtime ( &now );

  strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm );

  printf ( "%s\n", time_buffer );

  return;
# undef TIME_SIZE
}