# include <cmath>
# include <cstdlib>
# include <ctime>
# include <iomanip>
# include <iostream>

using namespace std;

# include "poisson_2d_exact.hpp"

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

//****************************************************************************80

int main ( )

//****************************************************************************80
//
//  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) );

  cout << "\n";
  cout << "poisson_2d_exact_test():\n";
  cout << "  C++ version\n";
  cout << "  Test poisson_2d_exact().\n";

  f = new double[n];
  r = new double[n];
  u = new double[n];
  ux = new double[n];
  uy = new double[n];
  uxx = new double[n];
  uxy = new double[n];
  uyy = new double[n];
  x = new double[n];
  y = new double[n];

  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];
  }

  cout << "  RMS norm of residuals = " << r8vec_norm_rms ( n, r ) << "\n";

  delete [] f;
  delete [] r;
  delete [] u;
  delete [] ux;
  delete [] uy;
  delete [] uxx;
  delete [] uxy;
  delete [] uyy;
  delete [] x;
  delete [] y;
//
//  Terminate.
//
  cout << "\n";
  cout << "poisson_2d_exact_test():\n";
  cout << "  Normal end of execution.\n";
  cout << "\n";
  timestamp ( );

  return 0;
}
//****************************************************************************80

double r8vec_norm_rms ( int n, double a[] )

//****************************************************************************80
//
//  Purpose:
//
//    r8vec_norm_rms() returns the RMS norm of an R8VEC.
//
//  Discussion:
//
//    An R8VEC is a vector of R8's.
//
//    The vector RMS norm is defined as:
//
//      R8VEC_RMS_NORM = 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.
//
//  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;
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    timestamp() prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the MIT license. 
//
//  Modified:
//
//    19 March 2018
//
//  Author:
//
//    John Burkardt
//
{
# define TIME_SIZE 40

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

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

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

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}