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

# include "golden_section.h"

int main ( );
double humps_fun ( double x );
double test_fun ( double x );
void timestamp ( );

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

int main ( )

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

    golden_section_test() tests golden_section().

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    23 February 2026

  Author:

    John Burkardt
*/
{
  double a;
  double b;
  int it;
  int n;
  double x_tol;

  timestamp ( );

  printf ( "\n" );
  printf ( "golden_section_test():\n" );
  printf ( "  C version\n" );
  printf ( "  golden_section() seeks a minimizer\n" );
  printf ( "  of a function f(x) in the interval [a,b],\n" );
  printf ( "  assuming f(x) is unimodal over [a,b],\n" );
/*
  humps(x) = 1 / ((x-0.3)^2 + 0.01) + 1 / ((x-0.9)^2 + 0.04) - 6.0
*/
  a = 0.3;
  b = 0.9;
  n = 25;
  x_tol = 0.000001;

  printf ( "\n" );
  printf ( "  f = humps_fun(x)\n" );
  printf ( "  f(%g) = %g\n", a, humps_fun ( a ) );
  printf ( "  f(%g) = %g\n", b, humps_fun ( b ) );
  printf ( "  iteration limit n = %d\n", n );
  printf ( "  x_tol = %g\n", x_tol );
  golden_section ( humps_fun, n, x_tol, &a, &b, &it );
  printf ( "\n" );
  printf ( "  Number of iterations: %d\n", it );
  printf ( "  f(%g) = %g\n", a, humps_fun ( a ) );
  printf ( "  f(%g) = %g\n", b, humps_fun ( b ) );
/*
  test_fun(x)=x^4+10*x*sin(x^2)
*/
  a = -2.0;
  b = 1.0;
  n = 35;
  x_tol = 0.000001;

  printf ( "\n" );
  printf ( "  f = test_fun(x)\n" );
  printf ( "  f(%g) = %g\n", a, test_fun ( a ) );
  printf ( "  f(%g) = %g\n", b, test_fun ( b ) );
  printf ( "  iteration limit n = %d\n", n );
  printf ( "  x_tol = %g\n", x_tol );
  golden_section ( test_fun, n, x_tol, &a, &b, &it );
  printf ( "\n" );
  printf ( "  Number of iterations: %d\n", it );
  printf ( "  f(%g) = %g\n", a, test_fun ( a ) );
  printf ( "  f(%g) = %g\n", b, test_fun ( b ) );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "golden_section_test():\n" );
  printf ( "  Normal end of execution.\n" );
  timestamp ( );

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

double humps_fun ( double x )

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

    humps_fun() evaluates a function used for demonstrations.

  Discussion:

    The "interesting" portion of the function is visible over the range
    0 <= x <= 2.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    29 June 2019

  Author:

    John Burkardt

  Input:

    double x: the evaluation point.

  Output:

    double humps_fun: the function value.
*/
{
  double value;

  value = 1.0 / ( pow ( x - 0.3, 2 ) + 0.01 )
        + 1.0 / ( pow ( x - 0.9, 2 ) + 0.04 ) - 6.0;

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

double test_fun ( double x )

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

 test_fun() evaluates a function used for demonstrations.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    23 February 2026

  Author:

    John Burkardt

  Input:

    double x: the evaluation point.

  Output:

    double test_fun: the function value.
*/
{
  double value;

  value = pow ( x, 4 ) + 10.0 * x * sin ( pow ( x, 2 ) );

  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
}