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

# include "poisson_2d_exact.h"

int main ( );
double r8vec_norm_rms ( int n, double x[] );
void timestamp ( );

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

int main ( )

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

    poisson_2d_exact_test() tests poisson_2d_exact().

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    06 June 2025

  Author:

    John Burkardt
*/
{
  double *f;
  int i;
  int n = 5;
  double *r;
  double *u;
  double *ux;
  double *uy;
  double *uxx;
  double *uxy;
  double *uyy;
  double *x;
  double *y;

  timestamp ( );

  srand ( time(0) );

  printf ( "\n" );
  printf ( "poisson_2d_exact_test():\n" );
  printf ( "  C version\n" );
  printf ( "  Test poisson_2d_exact().\n" );

  f = ( double * ) malloc ( n * sizeof ( double ) );
  r = ( double * ) malloc ( n * sizeof ( double ) );
  u = ( double * ) malloc ( n * sizeof ( double ) );
  ux = ( double * ) malloc ( n * sizeof ( double ) );
  uy = ( double * ) malloc ( n * sizeof ( double ) );
  uxx = ( double * ) malloc ( n * sizeof ( double ) );
  uxy = ( double * ) malloc ( n * sizeof ( double ) );
  uyy = ( double * ) malloc ( n * sizeof ( double ) );
  x = ( double * ) malloc ( n * sizeof ( double ) );
  y = ( double * ) malloc ( n * sizeof ( double ) );

  for ( i = 0; i < n; i++ )
  {
    x[i] = drand48 ( );
    y[i] = drand48 ( );
  }

  poisson_2d_exact ( n, x, y, u, ux, uy, uxx, uxy, uyy );
  for ( i = 0; i < n; i++ )
  {
    f[i] = 0.0;
  }

  for ( i = 0; i < n; i++ )
  {
    r[i] = uxx[i] + uyy[i] + f[i];
  }

  printf ( "  RMS norm of residuals = %g\n", r8vec_norm_rms ( n, r ) );

  free ( f );
  free ( r );
  free ( u );
  free ( ux );
  free ( uy );
  free ( uxx );
  free ( uxy );
  free ( uyy );
  free ( x );
  free ( y );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "poisson_2d_exact_test():\n" );
  printf ( "  Normal end of execution.\n" );
  printf ( "\n" );
  timestamp ( );

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

double r8vec_norm_rms ( int n, double a[] )

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

    r8vec_norm_rms() returns the RMS norm of an R8VEC.

  D iscussion:

    The vector RMS norm is defined as:

      R8VEC_NORM_RMS = sqrt ( sum ( 1 <= I <= N ) A(I)^2 / N )

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    26 October 2011

  Author:

    John Burkardt

  Input:

    int N, the number of entries in A.

    double A[N], the vector whose L2 norm is desired.

  Output:

    double R8VEC_NORM_RMS, the RMS norm of A.
*/
{
  int i;
  double v;

  v = 0.0;

  if ( 0 < n )
  {
    for ( i = 0; i < n; i++ )
    {
      v = v + a[i] * a[i];
    }
    v = sqrt ( v / ( double ) ( n ) );
  }

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

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
}