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

# include "sine_gordon_exact.h"

int main ( );
double *r8vec_linspace_new ( int n, double a, double b );
void timestamp ( );

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

int main ( )

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

    sine_gordon_exact_test() tests sine_gordon_exact().

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    02 May 2024

  Author:

    John Burkardt
*/
{
  double a;
  int i;
  int j;
  int nx = 6;
  int ny = 6;
  double r;
  double u;
  double uxy;
  double *x;
  double *y;

  timestamp ( );
  printf ( "\n" );
  printf ( "sine_gordon_exact_test():\n" );
  printf ( "  C version\n" );
  printf ( "  Test sine_gordon_exact().\n" );

  a = 1.5;

  printf ( "\n" );
  printf ( "  Parameters:\n" );
  printf ( "    a     = %g\n", a );

  printf ( "\n" );
  printf ( "  Evaluate solution and residual at selected points (X,Y)\n" );

  x = r8vec_linspace_new ( nx, 0.0, 1.0 );
  y = r8vec_linspace_new ( ny, 0.0, 1.0 );

  printf ( "\n" );
  printf ( "      X       Y       U(X,Y)      Resid(X,Y)\n" );
  printf ( "\n" );
  for ( j = 0; j < ny; j++ )
  {
    for ( i = 0; i < nx; i++ )
    {
      sine_gordon_exact ( a, x[i], y[j], &u, &uxy );
      r = sine_gordon_residual ( u, uxy );
      printf ( "%14.6f%14.6f%14.6g%14.6g\n", x[i], y[j], u, r );
    }
    printf ( "\n" );
  }

  free ( x );
  free ( y );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "sine_gordon_exact_test():\n" );
  printf ( "  Normal end of execution.\n" );
  printf ( "\n" );
  timestamp ( );

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

double *r8vec_linspace_new ( int n, double a, double b )

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

    r8vec_linspace_new() creates a vector of linearly spaced values.

  Discussion:

    An R8VEC is a vector of R8's.

    4 points evenly spaced between 0 and 12 will yield 0, 4, 8, 12.
 
    In other words, the interval is divided into N-1 even subintervals,
    and the endpoints of intervals are used as the points.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    29 March 2011

  Author:

    John Burkardt

  Input:

    int N, the number of entries in the vector.

    double A, B, the first and last entries.

  Output:

    double R8VEC_LINSPACE_NEW[N], a vector of linearly spaced data.
*/
{
  int i;
  double *x;

  x = ( double * ) malloc ( n * sizeof ( double ) );

  if ( n == 1 )
  {
    x[0] = ( a + b ) / 2.0;
  }
  else
  {
    for ( i = 0; i < n; i++ )
    {
      x[i] = ( ( double ) ( n - 1 - i ) * a 
             + ( double ) (         i ) * b ) 
             / ( double ) ( n - 1     );
    }
  }
  return x;
}
/******************************************************************************/

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
}