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

using namespace std;

int main ( int argc, char *argv[] );
void basis_mn_t3 ( double t[2*3], int n, double p[], double phi[], 
  double dphidx[], double dphidy[] );
void basis_mn_t6 ( double t[2*6], int n, double p[], double phi[], 
  double dphidx[], double dphidy[] );
char ch_cap ( char ch );
bool ch_eqi ( char ch1, char ch2 );
int ch_to_digit ( char ch );
double *fem2d_evaluate ( int fem_node_num, double fem_node_xy[], 
  int fem_element_order, int fem_element_num, int fem_element_node[], 
  int fem_element_neighbor[], int fem_value_dim, double fem_value[], 
  int sample_node_num, double sample_node_xy[] );
int file_column_count ( string input_filename );
int file_row_count ( string input_filename );
unsigned long get_seed ( );
int i4_max ( int i1, int i2 );
int i4_min ( int i1, int i2 );
int i4_uniform ( int b, int c, int *seed );
int i4col_compare ( int m, int n, int a[], int i, int j );
void i4col_sort_a ( int m, int n, int a[] );
void i4col_swap ( int m, int n, int a[], int irow1, int irow2 );
int *i4mat_data_read ( string input_filename, int m, int n );
void i4mat_header_read ( string input_filename, int *m, int *n );
float r4_abs ( float x );
int r4_nint ( float x );
float r4_uniform_01 ( int *seed );
double r8_huge ( );
double r8_max ( double x, double y );
double r8_min ( double x, double y );
int r8_nint ( double x );
double *r8mat_data_read ( string input_filename, int m, int n );
void r8mat_header_read ( string input_filename, int *m, int *n );
void r8mat_write ( string output_filename, int m, int n, double table[] );
int s_len_trim ( string s );
int s_to_i4 ( string s, int *last, bool *error );
bool s_to_i4vec ( string s, int n, int ivec[] );
double s_to_r8 ( string s, int *lchar, bool *error );
bool s_to_r8vec ( string s, int n, double rvec[] );
int s_word_count ( string s );
void sort_heap_external ( int n, int *indx, int *i, int *j, int isgn );
void timestamp ( );
int *triangulation_order3_neighbor_triangles ( int triangle_num,
  int triangle_node[] );
int *triangulation_order6_neighbor_triangles ( int triangle_num,
  int triangle_node[] );
void triangulation_search_delaunay ( int node_num, double node_xy[], int triangle_order,
  int triangle_num, int triangle_node[], int triangle_neighbor[], 
  double p[2], int *triangle, int *edge );

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

int main ( int argc, char *argv[] )

//****************************************************************************80
//
//  Purpose:
//
//    MAIN is the main program for FEM2D_SAMPLE.
//
//  Discussion:
//
//    FEM2D_SAMPLE reads files defining a 2D FEM representation of data,
//    and a set of sample points, and writes out a file containing the 
//    value of the finite element function at the sample points.
//
//  Usage:
//
//    fem2d_sample fem_prefix sample_prefix
//
//    where 'fem_prefix' is the common prefix for the FEM files:
//
//    * fem_prefix_nodes.txt,    the node coordinates.
//    * fem_prefix_elements.txt, the nodes that make up each element;
//    * fem_prefix_values.txt,   the values defined at each node.
//
//    and 'sample_prefix' is the common prefix for the SAMPLE files.
//    (the node file is input, and the values file is created by the program.)
//
//    * sample_prefix_nodes.txt,  the node coordinates where samples are desired.
//    * sample_prefix_values.txt, the values computed at each sample node.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    01 June 2009
//
//  Author:
//
//    John Burkardt
//
{
  string fem_element_filename;
  int *fem_element_neighbor;
  int *fem_element_node;
  int fem_element_num;
  int fem_element_order;
  int fem_node_dim;
  string fem_node_filename;
  int fem_node_num;
  double *fem_node_xy;
  string fem_prefix;
  double *fem_value;
  int fem_value_dim;
  string fem_value_filename;
  int fem_value_num;
  int sample_node_dim;
  string sample_node_filename;
  int sample_node_num;
  double *sample_node_xy;
  string sample_prefix;
  double *sample_value;
  int sample_value_dim;
  string sample_value_filename;
  int sample_value_num;

  timestamp ( );

  cout << "\n";
  cout << "FEM2D_SAMPLE\n";
  cout << "  C++ version.\n";
  cout << "\n";
  cout << "  Read files defining an FEM function of 2 arguments.\n";
  cout << "  Read a file of sample arguments.\n";
  cout << "  Write a file of function values at the arguments.\n";
//
//  Get the number of command line arguments.
//
  if ( 1 < argc )
  {
    fem_prefix = argv[1];
  }
  else
  {
    cout << "\n";
    cout << "Enter the FEM file prefix:\n";
    cin >> fem_prefix;
  }

  if ( 2 < argc )
  {
    sample_prefix = argv[2];
  }
  else
  {
    cout << "\n";
    cout << "Enter the sample file prefix:\n";
    cin >> sample_prefix;
  }
//
//  Create the filenames.
//
  fem_node_filename = fem_prefix + "_nodes.txt";
  fem_element_filename = fem_prefix + "_elements.txt";
  fem_value_filename = fem_prefix + "_values.txt";

  sample_node_filename = sample_prefix + "_nodes.txt";
  sample_value_filename = sample_prefix + "_values.txt";
//
//  Read the FEM data.
//
  r8mat_header_read ( fem_node_filename, &fem_node_dim, &fem_node_num );

  fem_node_xy = r8mat_data_read ( fem_node_filename, fem_node_dim, fem_node_num );

  cout << "\n";
  cout << "  The FEM node dimension is        " << fem_node_dim << "\n";
  cout << "  The FEM node number is           " << fem_node_num << "\n";

  if ( fem_node_dim != 2 )
  {
    cout << "\n";
    cout << "FEM2D_SAMPLE - Fatal error!\n";
    cout << "  Spatial dimension of the nodes is not 2.\n";
    exit ( 1 );
  }

  i4mat_header_read ( fem_element_filename, &fem_element_order, &fem_element_num );

  fem_element_node = i4mat_data_read ( fem_element_filename, fem_element_order, 
    fem_element_num );

  cout << "  The FEM element order is         " << fem_element_order << "\n";
  cout << "  The FEM element number is        " << fem_element_num << "\n";

  r8mat_header_read ( fem_value_filename, &fem_value_dim, &fem_value_num );

  cout << "  The FEM value order is           " << fem_value_dim << "\n";
  cout << "  the FEM value number is          " << fem_value_num << "\n";

  if ( fem_value_num != fem_node_num )
  {
    cout << "\n";
    cout << "FEM2D_SAMPLE - Fatal error!\n";
    cout << "  Number of values and nodes differ.\n";
    exit ( 1 );
  }
  fem_value = r8mat_data_read ( fem_value_filename, fem_value_dim, fem_value_num );
//
//  Create the element neighbor array.
//
  if ( fem_element_order == 3 )
  {
    fem_element_neighbor = triangulation_order3_neighbor_triangles ( 
      fem_element_num, fem_element_node );
  }
  else if ( fem_element_order == 6 )
  {
    fem_element_neighbor = triangulation_order6_neighbor_triangles ( 
      fem_element_num, fem_element_node );
  }
  else
  {
    cout << "\n";
    cout << "FEM2D_SAMPLE - Fatal error!\n";
    cout << "  The element order must be 3 or 6.\n";
    cout << "  But this data has element order = " << fem_element_order << "\n";
    exit ( 1 );
  }

  cout << "  The element neighbor array has been computed.\n";
//
//  Read the SAMPLE node data.
//
  r8mat_header_read ( sample_node_filename, &sample_node_dim, 
    &sample_node_num );

  sample_node_xy = r8mat_data_read ( sample_node_filename, sample_node_dim, 
    sample_node_num );

  cout << "\n";
  cout << "  Sample node spatial dimension is " << sample_node_dim << "\n";
  cout << "  Sample node number is            " << sample_node_num << "\n";

  if ( sample_node_dim != 2 )
  {
    cout << "\n";
    cout << "FEM2D_SAMPLE - Fatal error!\n";
    cout << "  Spatial dimension of the sample nodes is not 2.\n";
    exit ( 1 );
  }
//
//  Compute the SAMPLE values.
//
  sample_value_dim = fem_value_dim;
  sample_value_num = sample_node_num;

  sample_value = fem2d_evaluate ( fem_node_num, fem_node_xy, fem_element_order, 
    fem_element_num, fem_element_node, fem_element_neighbor, fem_value_dim, 
    fem_value, sample_node_num, sample_node_xy );
//
//  Write the sample values.
//
  r8mat_write ( sample_value_filename, sample_value_dim, sample_value_num, 
    sample_value );

  cout << "\n";
  cout << "  Interpolated FEM data written to \"" << sample_value_filename << "\"\n";
//
//  Free memory.
//
  delete [] fem_element_neighbor;
  delete [] fem_element_node;
  delete [] fem_node_xy;
  delete [] fem_value;
  delete [] sample_node_xy;
  delete [] sample_value;
//
//  Terminate.
//
  cout << "\n";
  cout << "FEM2D_SAMPLE\n";
  cout << "  Normal end of execution.\n";

  cout << "\n";
  timestamp ( );

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

void basis_mn_t3 ( double t[2*3], int n, double p[], double phi[], 
  double dphidx[], double dphidy[] )

//****************************************************************************80
//
//  Purpose:
//
//    BASIS_MN_T3: all bases at N points for a T3 element.
//
//  Discussion:
//
//    The routine is given the coordinates of the vertices of a triangle.
//    It works directly with these coordinates, and does not refer to a 
//    reference element.
//
//    The sides of the triangle DO NOT have to lie along a coordinate
//    axis.
//
//    The routine evaluates the basis functions associated with each vertex,
//    and their derivatives with respect to X and Y.
//
//  Physical Element T3: 
//       
//            3
//           . .
//          .   .
//         .     .
//        .       .
//       1---------2
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    09 February 2006
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double T[2*3], the coordinates of the vertices
//    of the triangle.  It is common to list these points in counter clockwise
//    order.
//
//    Input, int N, the number of evaluation points.
//
//    Input, double P[2*N], the points where the basis functions 
//    are to be evaluated.
//
//    Output, double PHI[3*N], the value of the basis functions 
//    at the evaluation points.
//
//    Output, double DPHIDX[3*N], DPHIDY[3*N], the value of the 
//    derivatives at the evaluation points.
//
//  Local parameters:
//
//    Local, double AREA, is (twice) the area of the triangle.
//
{
  double area;
  int i;
  int j;

  area = t[0+0*2] * ( t[1+1*2] - t[1+2*2] ) 
       + t[0+1*2] * ( t[1+2*2] - t[1+0*2] ) 
       + t[0+2*2] * ( t[1+0*2] - t[1+1*2] );

  if ( area == 0.0 )
  {
    cout << "\n";
    cout << "BASIS_MN_T3 - Fatal error!\n";
    cout << "  Element has zero area.\n";
    exit ( 1 );
  }

  for ( j = 0; j < n; j++ )
  {
    phi[0+j*3] =     (   ( t[0+2*2] - t[0+1*2] ) * ( p[1+j*2] - t[1+1*2] )     
                       - ( t[1+2*2] - t[1+1*2] ) * ( p[0+j*2] - t[0+1*2] ) );
    dphidx[0+j*3] =    - ( t[1+2*2] - t[1+1*2] );
    dphidy[0+j*3] =      ( t[0+2*2] - t[0+1*2] );

    phi[1+j*3] =     (   ( t[0+0*2] - t[0+2*2] ) * ( p[1+j*2] - t[1+2*2] )     
                       - ( t[1+0*2] - t[1+2*2] ) * ( p[0+j*2] - t[0+2*2] ) );
    dphidx[1+j*3] =    - ( t[1+0*2] - t[1+2*2] );
    dphidy[1+j*3] =      ( t[0+0*2] - t[0+2*2] );

    phi[2+j*3] =     (   ( t[0+1*2] - t[0+0*2] ) * ( p[1+j*2] - t[1+0*2] )     
                       - ( t[1+1*2] - t[1+0*2] ) * ( p[0+j*2] - t[0+0*2] ) );
    dphidx[2+j*3] =    - ( t[1+1*2] - t[1+0*2] );
    dphidy[2+j*3] =      ( t[0+1*2] - t[0+0*2] );
  }
//
//  Normalize.
//
  for ( j = 0; j < n; j++ )
  {
    for ( i = 0; i < 3; i++ )
    {
      phi[i+j*3]    = phi[i+j*3]    / area;
      dphidx[i+j*3] = dphidx[i+j*3] / area;
      dphidy[i+j*3] = dphidy[i+j*3] / area;
    }
  }

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

void basis_mn_t6 ( double t[2*6], int n, double p[], double phi[], 
  double dphidx[], double dphidy[] )

//****************************************************************************80
//
//  Purpose:
//
//    BASIS_MN_T6: all bases at N points for a T6 element.
//
//  Discussion:
//
//    The routine is given the coordinates of the vertices and midside
//    nodes of a triangle.  It works directly with these coordinates, and does 
//    not refer to a reference element.
//
//    This routine requires that the midside nodes be "in line"
//    with the vertices, that is, that the sides of the triangle be
//    straight.  However, the midside nodes do not actually have to
//    be halfway along the side of the triangle.  
//
//  The physical element T6:
//
//    This picture indicates the assumed ordering of the six nodes
//    of the triangle.
//
//    |
//    |   
//    |        3
//    |       . .
//    |      .   .
//    Y     6     5
//    |    .       .
//    |   .         .
//    |  1-----4-----2
//    |
//    +--------X-------->
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    12 February 2006
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double T[2*6], the nodal oordinates of the element.
//    It is common to list these points in counter clockwise order.
//
//    Input, int N, the number of evaluation points.
//
//    Input, double P[2*N], the coordinates of the point where
//    the basis functions are to be evaluated.
//
//    Output, double PHI[6*N], the value of the basis functions at P.
//
//    Output, double DPHIDX[6*N], DPHIDY[6*N], the value of the X 
//    and Y derivatives of the basis functions at P.
//
{
  double gn;
  double gx;
  double hn;
  double hx;
  int j;

  for ( j = 0; j < n; j++ )
  {
//
//  Basis function 1: PHI(X,Y) = G(3,2) * H(6,4) / normalization.
//
    gx = ( p[0+j*2] - t[0+1*2] ) * ( t[1+2*2] - t[1+1*2] ) 
       - ( t[0+2*2] - t[0+1*2] ) * ( p[1+j*2] - t[1+1*2] );

    gn = ( t[0+0*2] - t[0+1*2] ) * ( t[1+2*2] - t[1+1*2] ) 
       - ( t[0+2*2] - t[0+1*2] ) * ( t[1+0*2] - t[1+1*2] );

    hx = ( p[0+j*2] - t[0+3*2] ) * ( t[1+5*2] - t[1+3*2] ) 
       - ( t[0+5*2] - t[0+3*2] ) * ( p[1+j*2] - t[1+3*2] );

    hn = ( t[0+0*2] - t[0+3*2] ) * ( t[1+5*2] - t[1+3*2] ) 
       - ( t[0+5*2] - t[0+3*2] ) * ( t[1+0*2] - t[1+3*2] );

    phi[0+j*6] =     ( gx * hx ) / ( gn * hn );
    dphidx[0+j*6] =  (      ( t[1+2*2] - t[1+1*2] ) * hx 
                     + gx * ( t[1+5*2] - t[1+3*2] ) ) / ( gn * hn );
    dphidy[0+j*6] = -(      ( t[0+2*2] - t[0+1*2] ) * hx 
                     + gx * ( t[0+5*2] - t[0+3*2] ) ) / ( gn * hn );
//
//  Basis function 2: PHI(X,Y) = G(3,1) * H(4,5) / normalization.
//
    gx = ( p[0+j*2] - t[0+0*2] ) * ( t[1+2*2] - t[1+0*2] ) 
       - ( t[0+2*2] - t[0+0*2] ) * ( p[1+j*2] - t[1+0*2] );

    gn = ( t[0+1*2] - t[0+0*2] ) * ( t[1+2*2] - t[1+0*2] ) 
       - ( t[0+2*2] - t[0+0*2] ) * ( t[1+1*2] - t[1+0*2] );

    hx = ( p[0+j*2] - t[0+4*2] ) * ( t[1+3*2] - t[1+4*2] ) 
       - ( t[0+3*2] - t[0+4*2] ) * ( p[1+j*2] - t[1+4*2] );

    hn = ( t[0+1*2] - t[0+4*2] ) * ( t[1+3*2] - t[1+4*2] ) 
       - ( t[0+3*2] - t[0+4*2] ) * ( t[1+1*2] - t[1+4*2] );

    phi[1+j*6] = ( gx * hx ) / ( gn * hn );
    dphidx[1+j*6] =  (      ( t[1+2*2] - t[1+0*2] ) * hx 
                     + gx * ( t[1+3*2] - t[1+4*2] ) ) / ( gn * hn );
    dphidy[1+j*6] = -(      ( t[0+2*2] - t[0+0*2] ) * hx 
                     + gx * ( t[0+3*2] - t[0+4*2] ) ) / ( gn * hn );
//
//  Basis function 3: PHI(X,Y) = G(1,2) * H(5,6) / normalization.
//
    gx = ( p[0+j*2] - t[0+1*2] ) * ( t[1+0*2] - t[1+1*2] ) 
       - ( t[0+0*2] - t[0+1*2] ) * ( p[1+j*2] - t[1+1*2] );

    gn = ( t[0+2*2] - t[0+1*2] ) * ( t[1+0*2] - t[1+1*2] ) 
       - ( t[0+0*2] - t[0+1*2] ) * ( t[1+2*2] - t[1+1*2] );

    hx = ( p[0+j*2] - t[0+5*2] ) * ( t[1+4*2] - t[1+5*2] ) 
       - ( t[0+4*2] - t[0+5*2] ) * ( p[1+j*2] - t[1+5*2] );

    hn = ( t[0+2*2] - t[0+5*2] ) * ( t[1+4*2] - t[1+5*2] ) 
       - ( t[0+4*2] - t[0+5*2] ) * ( t[1+2*2] - t[1+5*2] );

    phi[2+j*6] = ( gx * hx ) / ( gn * hn );
    dphidx[2+j*6] =  (      ( t[1+0*2] - t[1+1*2] ) * hx 
                     + gx * ( t[1+4*2] - t[1+5*2] ) ) / ( gn * hn );
    dphidy[2+j*6] = -(      ( t[0+0*2] - t[0+1*2] ) * hx 
                     + gx * ( t[0+4*2] - t[0+5*2] ) ) / ( gn * hn );
//
//  Basis function 4: PHI(X,Y) = G(1,3) * H(2,3) / normalization.
//
    gx = ( p[0+j*2] - t[0+2*2] ) * ( t[1+0*2] - t[1+2*2] ) 
       - ( t[0+0*2] - t[0+2*2] ) * ( p[1+j*2] - t[1+2*2] );

    gn = ( t[0+3*2] - t[0+2*2] ) * ( t[1+0*2] - t[1+2*2] ) 
       - ( t[0+0*2] - t[0+2*2] ) * ( t[1+3*2] - t[1+2*2] );

    hx = ( p[0+j*2] - t[0+2*2] ) * ( t[1+1*2] - t[1+2*2] ) 
       - ( t[0+1*2] - t[0+2*2] ) * ( p[1+j*2] - t[1+2*2] );

    hn = ( t[0+3*2] - t[0+2*2] ) * ( t[1+1*2] - t[1+2*2] ) 
       - ( t[0+1*2] - t[0+2*2] ) * ( t[1+3*2] - t[1+2*2] );

    phi[3+j*6] = ( gx * hx ) / ( gn * hn );
    dphidx[3+j*6] =  (      ( t[1+0*2] - t[1+2*2] ) * hx 
                     + gx * ( t[1+1*2] - t[1+2*2] ) ) / ( gn * hn );
    dphidy[3+j*6] = -(      ( t[0+0*2] - t[0+2*2] ) * hx 
                     + gx * ( t[0+1*2] - t[0+2*2] ) ) / ( gn * hn );
//
//  Basis function 5: PHI(X,Y) = G(2,1) * H(3,1) / normalization.
//
    gx = ( p[0+j*2] - t[0+0*2] ) * ( t[1+1*2] - t[1+0*2] ) 
       - ( t[0+1*2] - t[0+0*2] ) * ( p[1+j*2] - t[1+0*2] );

    gn = ( t[0+4*2] - t[0+0*2] ) * ( t[1+1*2] - t[1+0*2] ) 
       - ( t[0+1*2] - t[0+0*2] ) * ( t[1+4*2] - t[1+0*2] );

    hx = ( p[0+j*2] - t[0+0*2] ) * ( t[1+2*2] - t[1+0*2] ) 
       - ( t[0+2*2] - t[0+0*2] ) * ( p[1+j*2] - t[1+0*2] );

    hn = ( t[0+4*2] - t[0+0*2] ) * ( t[1+2*2] - t[1+0*2] ) 
       - ( t[0+2*2] - t[0+0*2] ) * ( t[1+4*2] - t[1+0*2] );

    phi[4+j*6] = ( gx * hx ) / ( gn * hn );
    dphidx[4+j*6] =  (      ( t[1+1*2] - t[1+0*2] ) * hx 
                     + gx * ( t[1+2*2] - t[1+0*2] ) ) / ( gn * hn );
    dphidy[4+j*6] = -(      ( t[0+1*2] - t[0+0*2] ) * hx 
                     + gx * ( t[0+2*2] - t[0+0*2] ) ) / ( gn * hn );
//
//  Basis function 6: PHI(X,Y) = G(1,2) * H(3,2) / normalization.
//
    gx = ( p[0+j*2] - t[0+1*2] ) * ( t[1+0*2] - t[1+1*2] ) 
       - ( t[0+0*2] - t[0+1*2] ) * ( p[1+j*2] - t[1+1*2] );

    gn = ( t[0+5*2] - t[0+1*2] ) * ( t[1+0*2] - t[1+1*2] ) 
       - ( t[0+0*2] - t[0+1*2] ) * ( t[1+5*2] - t[1+1*2] );

    hx = ( p[0+j*2] - t[0+1*2] ) * ( t[1+2*2] - t[1+1*2] ) 
       - ( t[0+2*2] - t[0+1*2] ) * ( p[1+j*2] - t[1+1*2] );

    hn = ( t[0+5*2] - t[0+1*2] ) * ( t[1+2*2] - t[1+1*2] ) 
       - ( t[0+2*2] - t[0+1*2] ) * ( t[1+5*2] - t[1+1*2] );

    phi[5+j*6] = ( gx * hx ) / ( gn * hn );
    dphidx[5+j*6] =  (      ( t[1+0*2] - t[1+1*2] ) * hx 
                     + gx * ( t[1+2*2] - t[1+1*2] ) ) / ( gn * hn );
    dphidy[5+j*6] = -(      ( t[0+0*2] - t[0+1*2] ) * hx 
                     + gx * ( t[0+2*2] - t[0+1*2] ) ) / ( gn * hn );
  }

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

char ch_cap ( char ch )

//****************************************************************************80
//
//  Purpose:
//
//    CH_CAP capitalizes a single character.
//
//  Discussion:
//
//    This routine should be equivalent to the library "toupper" function.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    19 July 1998
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, char CH, the character to capitalize.
//
//    Output, char CH_CAP, the capitalized character.
//
{
  if ( 97 <= ch && ch <= 122 ) 
  {
    ch = ch - 32;
  }   

  return ch;
}
//****************************************************************************80

bool ch_eqi ( char ch1, char ch2 )

//****************************************************************************80
//
//  Purpose:
//
//    CH_EQI is true if two characters are equal, disregarding case.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    13 June 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, char CH1, CH2, the characters to compare.
//
//    Output, bool CH_EQI, is true if the two characters are equal,
//    disregarding case.
//
{
  if ( 97 <= ch1 && ch1 <= 122 ) 
  {
    ch1 = ch1 - 32;
  } 
  if ( 97 <= ch2 && ch2 <= 122 ) 
  {
    ch2 = ch2 - 32;
  }     

  return ( ch1 == ch2 );
}
//****************************************************************************80

int ch_to_digit ( char ch )

//****************************************************************************80
//
//  Purpose:
//
//    CH_TO_DIGIT returns the integer value of a base 10 digit.
//
//  Example:
//
//     CH  DIGIT
//    ---  -----
//    '0'    0
//    '1'    1
//    ...  ...
//    '9'    9
//    ' '    0
//    'X'   -1
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    13 June 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, char CH, the decimal digit, '0' through '9' or blank are legal.
//
//    Output, int CH_TO_DIGIT, the corresponding integer value.  If the character was
//    'illegal', then DIGIT is -1.
//
{
  int digit;

  if ( '0' <= ch && ch <= '9' )
  {
    digit = ch - '0';
  }
  else if ( ch == ' ' )
  {
    digit = 0;
  }
  else
  {
    digit = -1;
  }

  return digit;
}
//****************************************************************************80

double *fem2d_evaluate ( int fem_node_num, double fem_node_xy[], 
  int fem_element_order, int fem_element_num, int fem_element_node[], 
  int fem_element_neighbor[], int fem_value_dim, double fem_value[], 
  int sample_node_num, double sample_node_xy[] )

//****************************************************************************80
//
//  Purpose:
//
//    GRID_SAMPLE samples a (scalar) FE function on a T3 or T6 triangulation.
//
//  Discussion:
//
//    Note that the values of U returned are true values of the underlying
//    finite element function.  They are NOT produced by constructing some
//    other function that interpolates the data at the finite element nodes
//    (something which MATLAB's griddata function can easily do.)  Instead, 
//    each sampling node is located within one of the associated finite
//    element triangles, and the finite element function is developed and 
//    evaluated there.  
//
//    MATLAB's scattered data interpolation is wonderful, but it cannot
//    be guaranteed to reproduce the finite element function corresponding
//    to nodal data.  This routine can.
// 
//    So if you are using finite elements, then using THIS routine
//    (but not MATLAB's griddata function), what you see is what you have.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    01 June 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int FEM_NODE_NUM, the number of nodes.
//
//    Input, double FEM_NODE_XY[2*FEM_NODE_NUM], the coordinates of the nodes.
//
//    Input, int FEM_ELEMENT_ORDER, the order of the triangles, either
//    3 or 6.
//
//    Input, int FEM_ELEMENT_NUM, the number of triangles.
//
//    Input, int FEM_ELEMENT_NODE[FEM_ELEMENT_ORDER*FEM_ELEMENT_NUM], the
//    nodes that make up each element.
//
//    Input, int FEM_ELEMENT_NEIGHBOR[3*FEM_ELEMENT_NUM], the index of the
//    neighboring triangle on each side, or -1 if no neighbor there.
//
//    Input, int FEM_VALUE_DIM, the "dimension" of the values.
//
//    Input, double FEM_VALUE[FEM_VALUE_DIM*FEM_NODE_NUM], the finite element 
//    coefficient value at each node.
//
//    Input, int SAMPLE_NODE_NUM, the number of sample nodes.
//
//    Input, double SAMPLE_NODE_XY[2*SAMPLE_NODE_NUM], the sample nodes.
//
//    Output, double SAMPLE_VALUE[FEM_VALUE_DIM*SAMPLE_NODE_NUM],
//    the sampled values.
//
{
  double *b;
  double *dbdx;
  double *dbdy;
  double dot;
  int edge;
  int i;
  int j;
  int order;
  double p_xy[2];
  int t;
  double *sample_value;
  int *t_node;
  double *t_xy;

  b = new double[fem_element_order];
  dbdx = new double[fem_element_order];
  dbdy = new double[fem_element_order];
  sample_value = new double[fem_value_dim*sample_node_num];
  t_node = new int[fem_element_order];
  t_xy = new double[2*fem_element_order];
//
//  For each sample point: find the triangle T that contains it,
//  and evaluate the finite element function there.
//
  for ( j = 0; j < sample_node_num; j++ )
  {
    p_xy[0] = sample_node_xy[0+j*2];
    p_xy[1] = sample_node_xy[1+j*2];
//
//  Find the triangle T that contains the point.
//
    triangulation_search_delaunay ( fem_node_num, fem_node_xy, 
      fem_element_order, fem_element_num, fem_element_node, 
      fem_element_neighbor, p_xy, &t, &edge );
//
//  Evaluate the finite element basis functions at the point in T.
//
//  Note that in the following loop, we assume that FEM_ELEMENT_NODE
//  is 1-based, and that for convenience we can get away with making
//  T_NODE 0-based.
//
    for ( order = 0; order < fem_element_order; order++ )
    {
      t_node[order] = fem_element_node[order+(t-1)*fem_element_order] - 1;
    }

    for ( order = 0; order < fem_element_order; order++ )
    {
      t_xy[0+order*2] = fem_node_xy[0+t_node[order]*2];
      t_xy[1+order*2] = fem_node_xy[1+t_node[order]*2];
    }
    if ( fem_element_order == 3 )
    {
      basis_mn_t3 ( t_xy, 1, p_xy, b, dbdx, dbdy );
    }
    else if ( fem_element_order == 6 )
    {
      basis_mn_t6 ( t_xy, 1, p_xy, b, dbdx, dbdy );
    }
//
//  Multiply by the finite element values to get the sample values.
//
    for ( i = 0; i < fem_value_dim; i++ )
    {
      dot = 0.0;
      for ( order = 0; order < fem_element_order; order++ )
      {
        dot = dot + fem_value[i+t_node[order]] * b[order];
      }
      sample_value[i+j*fem_value_dim] = dot;
    }
  }
  delete [] b;
  delete [] dbdx;
  delete [] dbdy;
  delete [] t_node;
  delete [] t_xy;

  return sample_value;
}
//****************************************************************************80

int file_column_count ( string input_filename )

//****************************************************************************80
//
//  Purpose:
//
//    FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
//
//  Discussion:
//
//    The file is assumed to be a simple text file.
//
//    Most lines of the file is presumed to consist of COLUMN_NUM words, separated
//    by spaces.  There may also be some blank lines, and some comment lines,
//    which have a "#" in column 1.
//
//    The routine tries to find the first non-comment non-blank line and
//    counts the number of words in that line.
//
//    If all lines are blanks or comments, it goes back and tries to analyze
//    a comment line.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the file.
//
//    Output, int FILE_COLUMN_COUNT, the number of columns assumed 
//    to be in the file.
//
{
  int column_num;
  ifstream input;
  bool got_one;
  char line[255];
//
//  Open the file.
//
  input.open ( input_filename.c_str ( ) );

  if ( !input )
  {
    column_num = -1;
    cerr << "\n";
    cerr << "FILE_COLUMN_COUNT - Fatal error!\n";
    cerr << "  Could not open the file:\n";
    cerr << "  \"" << input_filename << "\"\n";
    return column_num;
  }
//
//  Read one line, but skip blank lines and comment lines.
//
  got_one = false;

  for ( ; ; )
  {
    input.getline ( line, sizeof ( line ) );

    if ( input.eof ( ) )
    {
      break;
    }

    if ( s_len_trim ( line ) == 0 )
    {
      continue;
    }

    if ( line[0] == '#' )
    {
      continue;
    }

    got_one = true;
    break;

  }

  if ( !got_one )
  {
    input.close ( );

    input.open ( input_filename.c_str ( ) );

    for ( ; ; )
    {
      input.getline ( line, sizeof ( line ) );

      if ( input.eof ( ) )
      {
        break;
      }

      if ( s_len_trim ( line ) == 0 )
      {
        continue;
      }

      got_one = true;
      break;

    }

  }

  input.close ( );

  if ( !got_one )
  {
    cerr << "\n";
    cerr << "FILE_COLUMN_COUNT - Warning!\n";
    cerr << "  The file does not seem to contain any data.\n";
    return -1;
  }

  column_num = s_word_count ( line );

  return column_num;
}
//****************************************************************************80

int file_row_count ( string input_filename )

//****************************************************************************80
//
//  Purpose:
//
//    FILE_ROW_COUNT counts the number of row records in a file.
//
//  Discussion:
//
//    It does not count lines that are blank, or that begin with a
//    comment symbol '#'.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the input file.
//
//    Output, int FILE_ROW_COUNT, the number of rows found.
//
{
  int comment_num;
  ifstream input;
  char line[255];
  int record_num;
  int row_num;

  row_num = 0;
  comment_num = 0;
  record_num = 0;

  input.open ( input_filename.c_str ( ) );

  if ( !input )
  {
    cerr << "\n";
    cerr << "FILE_ROW_COUNT - Fatal error!\n";
    cerr << "  Could not open the input file: \"" << input_filename << "\"\n";
    return (-1);
  }

  for ( ; ; )
  {
    input.getline ( line, sizeof ( line ) );

    if ( input.eof ( ) )
    {
      break;
    }

    record_num = record_num + 1;

    if ( line[0] == '#' )
    {
      comment_num = comment_num + 1;
      continue;
    }

    if ( s_len_trim ( line ) == 0 )
    {
      comment_num = comment_num + 1;
      continue;
    }

    row_num = row_num + 1;

  }

  input.close ( );

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

unsigned long get_seed ( )

//********************************************************************
//
//  Purpose:
//
//    GET_SEED returns a random seed for the random number generator.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    17 September 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Output, unsigned long GET_SEED, a random seed value.
//
{
# define UNSIGNED_LONG_MAX 4294967295UL

  time_t clock;
  int hours;
  int minutes;
  int seconds;
  struct tm *lt;
  static unsigned long seed = 0;
  time_t tloc;
//
//  If the internal seed is 0, generate a value based on the time.
//
  if ( seed == 0 )
  {
    clock = time ( &tloc );
    lt = localtime ( &clock );
//
//  Extract HOURS.
//
    hours = lt->tm_hour;
//
//  In case of 24 hour clocks, shift so that HOURS is between 1 and 12.
//
    if ( 12 < hours )
    {
      hours = hours - 12;
    }
//
//  Move HOURS to 0, 1, ..., 11
//
    hours = hours - 1;

    minutes = lt->tm_min;

    seconds = lt->tm_sec;

    seed = seconds + 60 * ( minutes + 60 * hours );
//
//  We want values in [1,43200], not [0,43199].
//
    seed = seed + 1;
//
//  Remap SEED from [1,43200] to [1,UNSIGNED_LONG_MAX].
//
    seed = ( unsigned long ) 
      ( ( ( double ) seed )
      * ( ( double ) UNSIGNED_LONG_MAX ) / ( 60.0 * 60.0 * 12.0 ) );
  }
//
//  Never use a seed of 0.
//
  if ( seed == 0 )
  {
    seed = 1;
  }

  return seed;

# undef UNSIGNED_LONG_MAX
}
//****************************************************************************80

int i4_max ( int i1, int i2 )

//****************************************************************************80
//
//  Purpose:
//
//    I4_MAX returns the maximum of two integers.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 May 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int I1, I2, two integers to be compared.
//
//    Output, int I4_MAX, the larger of I1 and I2.
//
{
  if ( i2 < i1 ) 
  {
    return i1;
  }
  else 
  {
    return i2;
  }

}
//****************************************************************************80

int i4_min ( int i1, int i2 )

//****************************************************************************80
//
//  Purpose:
//
//    I4_MIN returns the smaller of two integers.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 May 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int I1, I2, two integers to be compared.
//
//    Output, int I4_MIN, the smaller of I1 and I2.
//
{
  if ( i1 < i2 ) 
  {
    return i1;
  }
  else 
  {
    return i2;
  }

}
//****************************************************************************80

int i4_uniform ( int a, int b, int *seed )

//****************************************************************************80
//
//  Purpose:
//
//    I4_UNIFORM returns a scaled pseudorandom I4.
//
//  Discussion:
//
//    The pseudorandom number should be uniformly distributed
//    between A and B.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    12 November 2006
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    Paul Bratley, Bennett Fox, Linus Schrage,
//    A Guide to Simulation,
//    Springer Verlag, pages 201-202, 1983.
//
//    Pierre L'Ecuyer,
//    Random Number Generation,
//    in Handbook of Simulation,
//    edited by Jerry Banks,
//    Wiley Interscience, page 95, 1998.
//
//    Bennett Fox,
//    Algorithm 647:
//    Implementation and Relative Efficiency of Quasirandom
//    Sequence Generators,
//    ACM Transactions on Mathematical Software,
//    Volume 12, Number 4, pages 362-376, 1986.
//
//    Peter Lewis, Allen Goodman, James Miller
//    A Pseudo-Random Number Generator for the System/360,
//    IBM Systems Journal,
//    Volume 8, pages 136-143, 1969.
//
//  Parameters:
//
//    Input, int A, B, the limits of the interval.
//
//    Input/output, int *SEED, the "seed" value, which should NOT be 0.
//    On output, SEED has been updated.
//
//    Output, int I4_UNIFORM, a number between A and B.
//
{
  int k;
  float r;
  int value;

  if ( *seed == 0 )
  {
    cerr << "\n";
    cerr << "I4_UNIFORM - Fatal error!\n";
    cerr << "  Input value of SEED = 0.\n";
    exit ( 1 );
  }

  k = *seed / 127773;

  *seed = 16807 * ( *seed - k * 127773 ) - k * 2836;

  if ( *seed < 0 )
  {
    *seed = *seed + 2147483647;
  }

  r = ( float ) ( *seed ) * 4.656612875E-10;
//
//  Scale R to lie between A-0.5 and B+0.5.
//
  r = ( 1.0 - r ) * ( ( float ) ( i4_min ( a, b ) ) - 0.5 ) 
    +         r   * ( ( float ) ( i4_max ( a, b ) ) + 0.5 );
//
//  Use rounding to convert R to an integer between A and B.
//
  value = r4_nint ( r );

  value = i4_max ( value, i4_min ( a, b ) );
  value = i4_min ( value, i4_max ( a, b ) );

  return value;
}
//****************************************************************************80

int i4col_compare ( int m, int n, int a[], int i, int j )

//****************************************************************************80
//
//  Purpose:
//
//    I4COL_COMPARE compares columns I and J of an I4COL.
//
//  Example:
//
//    Input:
//
//      M = 3, N = 4, I = 2, J = 4
//
//      A = (
//        1  2  3  4
//        5  6  7  8
//        9 10 11 12 )
//
//    Output:
//
//      I4COL_COMPARE = -1
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    12 June 2005
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int M, N, the number of rows and columns.
//
//    Input, int A[M*N], an array of N columns of vectors of length M.
//
//    Input, int I, J, the columns to be compared.
//    I and J must be between 1 and N.
//
//    Output, int I4COL_COMPARE, the results of the comparison:
//    -1, column I < column J,
//     0, column I = column J,
//    +1, column J < column I.
//
{
  int k;
//
//  Check.
//
  if ( i < 1 )
  {
    cout << "\n";
    cout << "I4COL_COMPARE - Fatal error!\n";
    cout << "  Column index I = " << i << " is less than 1.\n";
    exit ( 1 );
  }

  if ( n < i )
  {
    cout << "\n";
    cout << "I4COL_COMPARE - Fatal error!\n";
    cout << "  N = " << n << " is less than column index I = " << i << ".\n";
    exit ( 1 );
  }

  if ( j < 1 )
  {
    cout << "\n";
    cout << "I4COL_COMPARE - Fatal error!\n";
    cout << "  Column index J = " << j << " is less than 1.\n";
    exit ( 1 );
  }

  if ( n < j )
  {
    cout << "\n";
    cout << "I4COL_COMPARE - Fatal error!\n";
    cout << "  N = " << n << " is less than column index J = " << j << ".\n";
    exit ( 1 );
  }

  if ( i == j )
  {
    return 0;
  }

  k = 1;

  while ( k <= m )
  {
    if ( a[k-1+(i-1)*m] < a[k-1+(j-1)*m] )
    {
      return (-1);
    }
    else if ( a[k-1+(j-1)*m] < a[k-1+(i-1)*m] )
    {
      return 1;
    }
    k = k + 1;
  }

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

void i4col_sort_a ( int m, int n, int a[] )

//****************************************************************************80
//
//  Purpose:
//
//    I4COL_SORT_A ascending sorts an I4COL.
//
//  Discussion:
//
//    In lexicographic order, the statement "X < Y", applied to two
//    vectors X and Y of length M, means that there is some index I, with
//    1 <= I <= M, with the property that
//
//      X(J) = Y(J) for J < I,
//    and
//      X(I) < Y(I).
//
//    In other words, X is less than Y if, at the first index where they
//    differ, the X value is less than the Y value.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    12 June 2005
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int M, the number of rows of A.
//
//    Input, int N, the number of columns of A.
//
//    Input/output, int A[M*N].
//    On input, the array of N columns of M vectors;
//    On output, the columns of A have been sorted in ascending
//    lexicographic order.
//
{
  int i;
  int indx;
  int isgn;
  int j;
//
//  Initialize.
//
  i = 0;
  indx = 0;
  isgn = 0;
  j = 0;
//
//  Call the external heap sorter.
//
  for ( ; ; )
  {
    sort_heap_external ( n, &indx, &i, &j, isgn );
//
//  Interchange the I and J objects.
//
    if ( 0 < indx )
    {
      i4col_swap ( m, n, a, i, j );
    }
//
//  Compare the I and J objects.
//
    else if ( indx < 0 )
    {
      isgn = i4col_compare ( m, n, a, i, j );
    }
    else if ( indx == 0 )
    {
      break;
    }

  }

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

void i4col_swap ( int m, int n, int a[], int icol1, int icol2 )

//****************************************************************************80
//
//  Purpose:
//
//    I4COL_SWAP swaps two columns of an I4COL.
//
//  Discussion:
//
//    The two dimensional information is stored as a one dimensional
//    array, by columns.
//
//    The row indices are 1 based, NOT 0 based!  However, a preprocessor
//    variable, called OFFSET, can be reset from 1 to 0 if you wish to
//    use 0-based indices.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    03 April 2005
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int M, N, the number of rows and columns.
//
//    Input/output, int A[M*N], an array of data.
//
//    Input, int ICOL1, ICOL2, the two columns to swap.
//    These indices should be between 1 and N.
//
{
# define OFFSET 1

  int i;
  int t;
//
//  Check.
//
  if ( icol1 - OFFSET < 0 || n-1 < icol1 - OFFSET )
  {
    cout << "\n";
    cout << "I4COL_SWAP - Fatal error!\n";
    cout << "  ICOL1 is out of range.\n";
    exit ( 1 );
  }

  if ( icol2 - OFFSET < 0 || n-1 < icol2 - OFFSET )
  {
    cout << "\n";
    cout << "I4COL_SWAP - Fatal error!\n";
    cout << "  ICOL2 is out of range.\n";
    exit ( 1 );
  }

  if ( icol1 == icol2 )
  {
    return;
  }
  for ( i = 0; i < m; i++ )
  {
    t                     = a[i+(icol1-OFFSET)*m];
    a[i+(icol1-OFFSET)*m] = a[i+(icol2-OFFSET)*m];
    a[i+(icol2-OFFSET)*m] = t;
  }

  return;
# undef OFFSET
}
//****************************************************************************80

int *i4mat_data_read ( string input_filename, int m, int n )

//****************************************************************************80
//
//  Purpose:
//
//    I4MAT_DATA_READ reads data from an I4MAT file.
//
//  Discussion:
//
//    The file is assumed to contain one record per line.
//
//    Records beginning with the '#' character are comments, and are ignored.
//    Blank lines are also ignored.
//
//    Each line that is not ignored is assumed to contain exactly (or at least)
//    M real numbers, representing the coordinates of a point.
//
//    There are assumed to be exactly (or at least) N such records.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the input file.
//
//    Input, int M, the number of spatial dimensions.
//
//    Input, int N, the number of points.  The program
//    will stop reading data once N values have been read.
//
//    Output, int I4MAT_DATA_READ[M*N], the table data.
//
{
  bool error;
  ifstream input;
  int i;
  int j;
  char line[255];
  int *table;
  int *x;

  input.open ( input_filename.c_str ( ) );

  if ( !input )
  {
    cerr << "\n";
    cerr << "I4MAT_DATA_READ - Fatal error!\n";
    cerr << "  Could not open the input file: \"" << input_filename << "\"\n";
    return NULL;
  }

  table = new int[m*n];

  x = new int[m];

  j = 0;

  while ( j < n )
  {
    input.getline ( line, sizeof ( line ) );

    if ( input.eof ( ) )
    {
      break;
    }

    if ( line[0] == '#' || s_len_trim ( line ) == 0 )
    {
      continue;
    }

    error = s_to_i4vec ( line, m, x );

    if ( error )
    {
      continue;
    }

    for ( i = 0; i < m; i++ )
    {
      table[i+j*m] = x[i];
    }
    j = j + 1;

  }

  input.close ( );

  delete [] x;

  return table;
}
//****************************************************************************80
 
void i4mat_header_read ( string input_filename, int *m, int *n )
 
//****************************************************************************80
//
//  Purpose:
//
//    I4MAT_HEADER_READ reads the header from an I4MAT file.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the input file.
//
//    Output, int *M, the number of spatial dimensions.
//
//    Output, int *N, the number of points
//
{
  *m = file_column_count ( input_filename );
 
  if ( *m <= 0 )
  {
    cerr << "\n";
    cerr << "I4MAT_HEADER_READ - Fatal error!\n";
    cerr << "  FILE_COLUMN_COUNT failed.\n";
    *n = -1;
    return;
  }
 
  *n = file_row_count ( input_filename );
 
  if ( *n <= 0 )
  {
    cerr << "\n";
    cerr << "I4MAT_HEADER_READ - Fatal error!\n";
    cerr << "  FILE_ROW_COUNT failed.\n";
    return;
  }
 
  return;
}
//****************************************************************************80

float r4_abs ( float x )

//****************************************************************************80
//
//  Purpose:
//
//    R4_ABS returns the absolute value of an R4.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    01 December 2006
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, float X, the quantity whose absolute value is desired.
//
//    Output, float R4_ABS, the absolute value of X.
//
{
  float value;

  if ( 0.0 <= x )
  {
    value = x;
  } 
  else
  {
    value = -x;
  }
  return value;
}
//****************************************************************************80

int r4_nint ( float x )

//****************************************************************************80
//
//  Purpose:
//
//    R4_NINT returns the nearest integer to an R4.
//
//  Example:
//
//        X         R4_NINT
//
//      1.3         1
//      1.4         1
//      1.5         1 or 2
//      1.6         2
//      0.0         0
//     -0.7        -1
//     -1.1        -1
//     -1.6        -2
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    14 November 2006
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, float X, the value.
//
//    Output, int R4_NINT, the nearest integer to X.
//
{
  int value;

  if ( x < 0.0 )
  {
    value = - ( int ) ( r4_abs ( x ) + 0.5 );
  }
  else
  {
    value =   ( int ) ( r4_abs ( x ) + 0.5 );
  }

  return value;
}
//****************************************************************************80

float r4_uniform_01 ( int *seed )

//****************************************************************************80
//
//  Purpose:
//
//    R4_UNIFORM_01 returns a unit pseudorandom R4.
//
//  Discussion:
//
//    This routine implements the recursion
//
//      seed = 16807 * seed mod ( 2**31 - 1 )
//      r4_uniform_01 = seed / ( 2**31 - 1 )
//
//    The integer arithmetic never requires more than 32 bits,
//    including a sign bit.
//
//    If the initial seed is 12345, then the first three computations are
//
//      Input     Output      R4_UNIFORM_01
//      SEED      SEED
//
//         12345   207482415  0.096616
//     207482415  1790989824  0.833995
//    1790989824  2035175616  0.947702
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    16 November 2004
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    Paul Bratley, Bennett Fox, Linus Schrage,
//    A Guide to Simulation,
//    Springer Verlag, pages 201-202, 1983.
//
//    Pierre L'Ecuyer,
//    Random Number Generation,
//    in Handbook of Simulation
//    edited by Jerry Banks,
//    Wiley Interscience, page 95, 1998.
//
//    Bennett Fox,
//    Algorithm 647:
//    Implementation and Relative Efficiency of Quasirandom
//    Sequence Generators,
//    ACM Transactions on Mathematical Software,
//    Volume 12, Number 4, pages 362-376, 1986.
//
//    Peter Lewis, Allen Goodman, James Miller,
//    A Pseudo-Random Number Generator for the System/360,
//    IBM Systems Journal,
//    Volume 8, pages 136-143, 1969.
//
//  Parameters:
//
//    Input/output, int *SEED, the "seed" value.  Normally, this
//    value should not be 0.  On output, SEED has been updated.
//
//    Output, float R4_UNIFORM_01, a new pseudorandom variate, strictly between
//    0 and 1.
//
{
  int k;
  float r;

  if ( *seed == 0 )
  {
    cerr << "\n";
    cerr << "R4_UNIFORM_01 - Fatal error!\n";
    cerr << "  Input value of SEED = 0.\n";
    exit ( 1 );
  }

  k = *seed / 127773;

  *seed = 16807 * ( *seed - k * 127773 ) - k * 2836;

  if ( *seed < 0 )
  {
    *seed = *seed + 2147483647;
  }
//
//  Although SEED can be represented exactly as a 32 bit integer,
//  it generally cannot be represented exactly as a 32 bit real number!
//
  r = ( float ) ( *seed ) * 4.656612875E-10;

  return r;
}
//****************************************************************************80

double r8_huge ( )

//****************************************************************************80
//
//  Purpose:
//
//    R8_HUGE returns a "huge" R8.
//
//  Discussion:
//
//    The value returned by this function is NOT required to be the
//    maximum representable R8.  This value varies from machine to machine,
//    from compiler to compiler, and may cause problems when being printed.
//    We simply want a "very large" but non-infinite number.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    06 October 2007
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Output, double R8_HUGE, a "huge" R8 value.
//
{
  double value;

  value = 1.0E+30;

  return value;
}
//****************************************************************************80

double r8_max ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_MAX returns the maximum of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    18 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_MAX, the maximum of X and Y.
//
{
  double value;

  if ( y < x )
  {
    value = x;
  } 
  else
  {
    value = y;
  }
  return value;
}
//****************************************************************************80

double r8_min ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_MIN returns the minimum of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    31 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_MIN, the minimum of X and Y.
//
{
  double value;

  if ( y < x )
  {
    value = y;
  } 
  else
  {
    value = x;
  }
  return value;
}
//****************************************************************************80

int r8_nint ( double x )

//****************************************************************************80
//
//  Purpose:
//
//    R8_NINT returns the nearest integer to an R8.
//
//  Example:
//
//        X         Value
//
//      1.3         1
//      1.4         1
//      1.5         1 or 2
//      1.6         2
//      0.0         0
//     -0.7        -1
//     -1.1        -1
//     -1.6        -2
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    26 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, the value.
//
//    Output, int R8_NINT, the nearest integer to X.
//
{
  int s;
  int value;

  if ( x < 0.0 )
  {
    s = -1;
  }
  else
  {
    s = 1;
  }
  value = s * ( int ) ( fabs ( x ) + 0.5 );

  return value;
}
//****************************************************************************80

double *r8mat_data_read ( string input_filename, int m, int n )

//****************************************************************************80
//
//  Purpose:
//
//    R8MAT_DATA_READ reads the data from an R8MAT file.
//
//  Discussion:
//
//    The file is assumed to contain one record per line.
//
//    Records beginning with '#' are comments, and are ignored.
//    Blank lines are also ignored.
//
//    Each line that is not ignored is assumed to contain exactly (or at least)
//    M real numbers, representing the coordinates of a point.
//
//    There are assumed to be exactly (or at least) N such records.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the input file.
//
//    Input, int M, the number of spatial dimensions.
//
//    Input, int N, the number of points.  The program
//    will stop reading data once N values have been read.
//
//    Output, double R8MAT_DATA_READ[M*N], the table data.
//
{
  bool error;
  ifstream input;
  int i;
  int j;
  string line;
  double *table;
  double *x;

  input.open ( input_filename.c_str ( ) );

  if ( !input )
  {
    cerr << "\n";
    cerr << "R8MAT_DATA_READ - Fatal error!\n";
    cerr << "  Could not open the input file: \"" << input_filename << "\"\n";
    return NULL;
  }

  table = new double[m*n];

  x = new double[m];

  j = 0;

  while ( j < n )
  {
    getline ( input, line );

    if ( input.eof ( ) )
    {
      break;
    }

    if ( line[0] == '#' || s_len_trim ( line ) == 0 )
    {
      continue;
    }

    error = s_to_r8vec ( line, m, x );

    if ( error )
    {
      continue;
    }

    for ( i = 0; i < m; i++ )
    {
      table[i+j*m] = x[i];
    }
    j = j + 1;

  }

  input.close ( );

  delete [] x;

  return table;
}
//****************************************************************************80
 
void r8mat_header_read ( string input_filename, int *m, int *n )
 
//****************************************************************************80
//
//  Purpose:
//
//    R8MAT_HEADER_READ reads the header from an R8MAT file.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    23 February 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string INPUT_FILENAME, the name of the input file.
//
//    Output, int *M, the number of spatial dimensions.
//
//    Output, int *N, the number of points.
//
{
  *m = file_column_count ( input_filename );

  if ( *m <= 0 )
  {
    cerr << "\n";
    cerr << "R8MAT_HEADER_READ - Fatal error!\n";
    cerr << "  FILE_COLUMN_COUNT failed.\n";
    *n = -1;
    return;
  }

  *n = file_row_count ( input_filename );

  if ( *n <= 0 )
  {
    cerr << "\n";
    cerr << "R8MAT_HEADER_READ - Fatal error!\n";
    cerr << "  FILE_ROW_COUNT failed.\n";
    return;
  }

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

void r8mat_write ( string output_filename, int m, int n, double table[] )

//****************************************************************************80
//
//  Purpose:
//
//    R8MAT_WRITE writes an R8MAT file.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    29 June 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string OUTPUT_FILENAME, the output filename.
//
//    Input, int M, the spatial dimension.
//
//    Input, int N, the number of points.
//
//    Input, double TABLE[M*N], the table data.
//
{
  int i;
  int j;
  ofstream output;
//
//  Open the file.
//
  output.open ( output_filename.c_str ( ) );

  if ( !output )
  {
    cerr << "\n";
    cerr << "R8MAT_WRITE - Fatal error!\n";
    cerr << "  Could not open the output file.\n";
    return;
  }
//
//  Write the data.
//  For greater precision, try
//
//    output << "  " << setw(24) << setprecision(16) << table[i+j*m];
//
  for ( j = 0; j < n; j++ )
  {
    for ( i = 0; i < m; i++ )
    {
      output << "  " << setw(10) << table[i+j*m];
    }
    output << "\n";
  }
//
//  Close the file.
//
  output.close ( );

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

int s_len_trim ( string s )

//****************************************************************************80
//
//  Purpose:
//
//    S_LEN_TRIM returns the length of a string to the last nonblank.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, a string.
//
//    Output, int S_LEN_TRIM, the length of the string to the last nonblank.
//    If S_LEN_TRIM is 0, then the string is entirely blank.
//
{
  int n;

  n = s.length ( );

  while ( 0 < n ) 
  {
    if ( s[n-1] != ' ' )
    {
      return n;
    }
    n = n - 1;
  }

  return n;
}
//****************************************************************************80

int s_to_i4 ( string s, int *last, bool *error )

//****************************************************************************80
//
//  Purpose:
//
//    S_TO_I4 reads an I4 from a string.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, a string to be examined.
//
//    Output, int *LAST, the last character of S used to make IVAL.
//
//    Output, bool *ERROR is TRUE if an error occurred.
//
//    Output, int *S_TO_I4, the integer value read from the string.
//    If the string is blank, then IVAL will be returned 0.
//
{
  char c;
  int i;
  int isgn;
  int istate;
  int ival;

  *error = false;
  istate = 0;
  isgn = 1;
  i = 0;
  ival = 0;

  for ( ; ; ) 
  {
    c = s[i];
    i = i + 1;
//
//  Haven't read anything.
//
    if ( istate == 0 )
    {
      if ( c == ' ' )
      {
      }
      else if ( c == '-' )
      {
        istate = 1;
        isgn = -1;
      }
      else if ( c == '+' )
      {
        istate = 1;
        isgn = + 1;
      }
      else if ( '0' <= c && c <= '9' )
      {
        istate = 2;
        ival = c - '0';
      }
      else
      {
        *error = true;
        return ival;
      }
    }
//
//  Have read the sign, expecting digits.
//
    else if ( istate == 1 )
    {
      if ( c == ' ' )
      {
      }
      else if ( '0' <= c && c <= '9' )
      {
        istate = 2;
        ival = c - '0';
      }
      else
      {
        *error = true;
        return ival;
      }
    }
//
//  Have read at least one digit, expecting more.
//
    else if ( istate == 2 )
    {
      if ( '0' <= c && c <= '9' )
      {
        ival = 10 * (ival) + c - '0';
      }
      else
      {
        ival = isgn * ival;
        *last = i - 1;
        return ival;
      }

    }
  }
//
//  If we read all the characters in the string, see if we're OK.
//
  if ( istate == 2 )
  {
    ival = isgn * ival;
    *last = s_len_trim ( s );
  }
  else
  {
    *error = true;
    *last = 0;
  }

  return ival;
}
//****************************************************************************80

bool s_to_i4vec ( string s, int n, int ivec[] )

//****************************************************************************80
//
//  Purpose:
//
//    S_TO_I4VEC reads an I4VEC from a string.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, the string to be read.
//
//    Input, int N, the number of values expected.
//
//    Output, int IVEC[N], the values read from the string.
//
//    Output, bool S_TO_I4VEC, is TRUE if an error occurred.
//
{
  int begin;
  bool error;
  int i;
  int lchar;
  int length;

  begin = 0;
  length = s.length ( );
  error = 0;

  for ( i = 0; i < n; i++ )
  {
    ivec[i] = s_to_i4 ( s.substr(begin,length), &lchar, &error );

    if ( error )
    {
      return error;
    }
    begin = begin + lchar;
    length = length - lchar;
  }

  return error;
}
//****************************************************************************80

double s_to_r8 ( string s, int *lchar, bool *error )

//****************************************************************************80
//
//  Purpose:
//
//    S_TO_R8 reads an R8 from a string.
//
//  Discussion:
//
//    This routine will read as many characters as possible until it reaches
//    the end of the string, or encounters a character which cannot be
//    part of the real number.
//
//    Legal input is:
//
//       1 blanks,
//       2 '+' or '-' sign,
//       2.5 spaces
//       3 integer part,
//       4 decimal point,
//       5 fraction part,
//       6 'E' or 'e' or 'D' or 'd', exponent marker,
//       7 exponent sign,
//       8 exponent integer part,
//       9 exponent decimal point,
//      10 exponent fraction part,
//      11 blanks,
//      12 final comma or semicolon.
//
//    with most quantities optional.
//
//  Example:
//
//    S                 R
//
//    '1'               1.0
//    '     1   '       1.0
//    '1A'              1.0
//    '12,34,56'        12.0
//    '  34 7'          34.0
//    '-1E2ABCD'        -100.0
//    '-1X2ABCD'        -1.0
//    ' 2E-1'           0.2
//    '23.45'           23.45
//    '-4.2E+2'         -420.0
//    '17d2'            1700.0
//    '-14e-2'         -0.14
//    'e2'              100.0
//    '-12.73e-9.23'   -12.73 * 10.0**(-9.23)
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, the string containing the
//    data to be read.  Reading will begin at position 1 and
//    terminate at the end of the string, or when no more
//    characters can be read to form a legal real.  Blanks,
//    commas, or other nonnumeric data will, in particular,
//    cause the conversion to halt.
//
//    Output, int *LCHAR, the number of characters read from
//    the string to form the number, including any terminating
//    characters such as a trailing comma or blanks.
//
//    Output, bool *ERROR, is true if an error occurred.
//
//    Output, double S_TO_R8, the real value that was read from the string.
//
{
  char c;
  int ihave;
  int isgn;
  int iterm;
  int jbot;
  int jsgn;
  int jtop;
  int nchar;
  int ndig;
  double r;
  double rbot;
  double rexp;
  double rtop;
  char TAB = 9;

  nchar = s_len_trim ( s );
  *error = false;
  r = 0.0;
  *lchar = -1;
  isgn = 1;
  rtop = 0.0;
  rbot = 1.0;
  jsgn = 1;
  jtop = 0;
  jbot = 1;
  ihave = 1;
  iterm = 0;

  for ( ; ; )
  {
    c = s[*lchar+1];
    *lchar = *lchar + 1;
//
//  Blank or TAB character.
//
    if ( c == ' ' || c == TAB )
    {
      if ( ihave == 2 )
      {
      }
      else if ( ihave == 6 || ihave == 7 )
      {
        iterm = 1;
      }
      else if ( 1 < ihave )
      {
        ihave = 11;
      }
    }
//
//  Comma.
//
    else if ( c == ',' || c == ';' )
    {
      if ( ihave != 1 )
      {
        iterm = 1;
        ihave = 12;
        *lchar = *lchar + 1;
      }
    }
//
//  Minus sign.
//
    else if ( c == '-' )
    {
      if ( ihave == 1 )
      {
        ihave = 2;
        isgn = -1;
      }
      else if ( ihave == 6 )
      {
        ihave = 7;
        jsgn = -1;
      }
      else
      {
        iterm = 1;
      }
    }
//
//  Plus sign.
//
    else if ( c == '+' )
    {
      if ( ihave == 1 )
      {
        ihave = 2;
      }
      else if ( ihave == 6 )
      {
        ihave = 7;
      }
      else
      {
        iterm = 1;
      }
    }
//
//  Decimal point.
//
    else if ( c == '.' )
    {
      if ( ihave < 4 )
      {
        ihave = 4;
      }
      else if ( 6 <= ihave && ihave <= 8 )
      {
        ihave = 9;
      }
      else
      {
        iterm = 1;
      }
    }
//
//  Exponent marker.
//
    else if ( ch_eqi ( c, 'E' ) || ch_eqi ( c, 'D' ) )
    {
      if ( ihave < 6 )
      {
        ihave = 6;
      }
      else
      {
        iterm = 1;
      }
    }
//
//  Digit.
//
    else if ( ihave < 11 && '0' <= c && c <= '9' )
    {
      if ( ihave <= 2 )
      {
        ihave = 3;
      }
      else if ( ihave == 4 )
      {
        ihave = 5;
      }
      else if ( ihave == 6 || ihave == 7 )
      {
        ihave = 8;
      }
      else if ( ihave == 9 )
      {
        ihave = 10;
      }

      ndig = ch_to_digit ( c );

      if ( ihave == 3 )
      {
        rtop = 10.0 * rtop + ( double ) ndig;
      }
      else if ( ihave == 5 )
      {
        rtop = 10.0 * rtop + ( double ) ndig;
        rbot = 10.0 * rbot;
      }
      else if ( ihave == 8 )
      {
        jtop = 10 * jtop + ndig;
      }
      else if ( ihave == 10 )
      {
        jtop = 10 * jtop + ndig;
        jbot = 10 * jbot;
      }

    }
//
//  Anything else is regarded as a terminator.
//
    else
    {
      iterm = 1;
    }
//
//  If we haven't seen a terminator, and we haven't examined the
//  entire string, go get the next character.
//
    if ( iterm == 1 || nchar <= *lchar + 1 )
    {
      break;
    }

  }
//
//  If we haven't seen a terminator, and we have examined the
//  entire string, then we're done, and LCHAR is equal to NCHAR.
//
  if ( iterm != 1 && (*lchar) + 1 == nchar )
  {
    *lchar = nchar;
  }
//
//  Number seems to have terminated.  Have we got a legal number?
//  Not if we terminated in states 1, 2, 6 or 7!
//
  if ( ihave == 1 || ihave == 2 || ihave == 6 || ihave == 7 )
  {
    *error = true;
    return r;
  }
//
//  Number seems OK.  Form it.
//
  if ( jtop == 0 )
  {
    rexp = 1.0;
  }
  else
  {
    if ( jbot == 1 )
    {
      rexp = pow ( 10.0, jsgn * jtop );
    }
    else
    {
      rexp = jsgn * jtop;
      rexp = rexp / jbot;
      rexp = pow ( 10.0, rexp );
    }

  }

  r = isgn * rexp * rtop / rbot;

  return r;
}
//****************************************************************************80

bool s_to_r8vec ( string s, int n, double rvec[] )

//****************************************************************************80
//
//  Purpose:
//
//    S_TO_R8VEC reads an R8VEC from a string.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, the string to be read.
//
//    Input, int N, the number of values expected.
//
//    Output, double RVEC[N], the values read from the string.
//
//    Output, bool S_TO_R8VEC, is true if an error occurred.
//
{
  int begin;
  bool error;
  int i;
  int lchar;
  int length;

  begin = 0;
  length = s.length ( );
  error = 0;

  for ( i = 0; i < n; i++ )
  {
    rvec[i] = s_to_r8 ( s.substr(begin,length), &lchar, &error );

    if ( error )
    {
      return error;
    }
    begin = begin + lchar;
    length = length - lchar;
  }

  return error;
}
//****************************************************************************80

int s_word_count ( string s )

//****************************************************************************80
//
//  Purpose:
//
//    S_WORD_COUNT counts the number of "words" in a string.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, string S, the string to be examined.
//
//    Output, int S_WORD_COUNT, the number of "words" in the string.
//    Words are presumed to be separated by one or more blanks.
//
{
  bool blank;
  int char_count;
  int i;
  int word_count;

  word_count = 0;
  blank = true;

  char_count = s.length ( );

  for ( i = 0; i < char_count; i++ )
  {
    if ( isspace ( s[i] ) )
    {
      blank = true;
    }
    else if ( blank )
    {
      word_count = word_count + 1;
      blank = false;
    }
  }

  return word_count;
}
//****************************************************************************80

void sort_heap_external ( int n, int *indx, int *i, int *j, int isgn )

//****************************************************************************80
//
//  Purpose:
//
//    SORT_HEAP_EXTERNAL externally sorts a list of items into ascending order.
//
//  Discussion:
//
//    The actual list is not passed to the routine.  Hence it may
//    consist of integers, reals, numbers, names, etc.  The user,
//    after each return from the routine, will be asked to compare or
//    interchange two items.
//
//    The current version of this code mimics the FORTRAN version,
//    so the values of I and J, in particular, are FORTRAN indices.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    05 February 2004
//
//  Author:
//
//    Original FORTRAN77 version by Albert Nijenhuis, Herbert Wilf.
//    C++ version by John Burkardt.
//
//  Reference:
//
//    Albert Nijenhuis, Herbert Wilf,
//    Combinatorial Algorithms,
//    Academic Press, 1978, second edition,
//    ISBN 0-12-519260-6.
//
//  Parameters:
//
//    Input, int N, the length of the input list.
//
//    Input/output, int *INDX.
//    The user must set INDX to 0 before the first call.
//    On return,
//      if INDX is greater than 0, the user must interchange
//      items I and J and recall the routine.
//      If INDX is less than 0, the user is to compare items I
//      and J and return in ISGN a negative value if I is to
//      precede J, and a positive value otherwise.
//      If INDX is 0, the sorting is done.
//
//    Output, int *I, *J.  On return with INDX positive,
//    elements I and J of the user's list should be
//    interchanged.  On return with INDX negative, elements I
//    and J are to be compared by the user.
//
//    Input, int ISGN. On return with INDX negative, the
//    user should compare elements I and J of the list.  If
//    item I is to precede item J, set ISGN negative,
//    otherwise set ISGN positive.
//
{
  static int i_save = 0;
  static int j_save = 0;
  static int k = 0;
  static int k1 = 0;
  static int n1 = 0;
//
//  INDX = 0: This is the first call.
//
  if ( *indx == 0 )
  {

    i_save = 0;
    j_save = 0;
    k = n / 2;
    k1 = k;
    n1 = n;
  }
//
//  INDX < 0: The user is returning the results of a comparison.
//
  else if ( *indx < 0 )
  {
    if ( *indx == -2 ) 
    {
      if ( isgn < 0 ) 
      {
        i_save = i_save + 1;
      }
      j_save = k1;
      k1 = i_save;
      *indx = -1;
      *i = i_save;
      *j = j_save;
      return;
    }

    if ( 0 < isgn ) 
    {
      *indx = 2;
      *i = i_save;
      *j = j_save;
      return;
    }

    if ( k <= 1 ) 
    {
      if ( n1 == 1 ) 
      {
        i_save = 0;
        j_save = 0;
        *indx = 0;
      }
      else 
      {
        i_save = n1;
        j_save = 1;
        n1 = n1 - 1;
        *indx = 1;
      }
      *i = i_save;
      *j = j_save;
      return;
    }
    k = k - 1;
    k1 = k;
  }
//
//  0 < INDX: the user was asked to make an interchange.
//
  else if ( *indx == 1 ) 
  {
    k1 = k;
  }

  for ( ; ; )
  {

    i_save = 2 * k1;

    if ( i_save == n1 ) 
    {
      j_save = k1;
      k1 = i_save;
      *indx = -1;
      *i = i_save;
      *j = j_save;
      return;
    }
    else if ( i_save <= n1 ) 
    {
      j_save = i_save + 1;
      *indx = -2;
      *i = i_save;
      *j = j_save;
      return;
    }

    if ( k <= 1 ) 
    {
      break;
    }

    k = k - 1;
    k1 = k;
  }

  if ( n1 == 1 ) 
  {
    i_save = 0;
    j_save = 0;
    *indx = 0;
    *i = i_save;
    *j = j_save;
  }
  else 
  {
    i_save = n1;
    j_save = 1;
    n1 = n1 - 1;
    *indx = 1;
    *i = i_save;
    *j = j_save;
  }

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

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    TIMESTAMP prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    May 31 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    02 October 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    None
//
{
# 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 );

  cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}
//****************************************************************************80

int *triangulation_order3_neighbor_triangles ( int triangle_num,
  int triangle_node[] )

//****************************************************************************80
//
//  Purpose:
//
//    TRIANGULATION_ORDER3_NEIGHBOR_TRIANGLES determines triangle neighbors.
//
//  Discussion:
//
//    A triangulation of a set of nodes can be completely described by
//    the coordinates of the nodes, and the list of nodes that make up
//    each triangle.  However, in some cases, it is necessary to know
//    triangle adjacency information, that is, which triangle, if any,
//    is adjacent to a given triangle on a particular side.
//
//    This routine creates a data structure recording this information.
//
//    The primary amount of work occurs in sorting a list of 3 * TRIANGLE_NUM
//    data items.
//
//    This routine was modified to work with columns rather than rows.
//
//  Example:
//
//    The input information from TRIANGLE_NODE:
//
//    Triangle   Nodes
//    --------   ---------------
//     1         3      4      1
//     2         3      1      2
//     3         3      2      8
//     4         2      1      5
//     5         8      2     13
//     6         8     13      9
//     7         3      8      9
//     8        13      2      5
//     9         9     13      7
//    10         7     13      5
//    11         6      7      5
//    12         9      7      6
//    13        10      9      6
//    14         6      5     12
//    15        11      6     12
//    16        10      6     11
//
//    The output information in TRIANGLE_NEIGHBOR:
//
//    Triangle  Neighboring Triangles
//    --------  ---------------------
//
//     1        -1     -1      2
//     2         1      4      3
//     3         2      5      7
//     4         2     -1      8
//     5         3      8      6
//     6         5      9      7
//     7         3      6     -1
//     8         5      4     10
//     9         6     10     12
//    10         9      8     11
//    11        12     10     14
//    12         9     11     13
//    13        -1     12     16
//    14        11     -1     15
//    15        16     14     -1
//    16        13     15     -1
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    01 June 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int TRIANGLE_NUM, the number of triangles.
//
//    Input, int TRIANGLE_NODE[3*TRIANGLE_NUM], the nodes that make up each 
//    triangle.
//
//    Output, int TRIANGLE_ORDER3_NEIGHBOR_TRIANGLES[3*TRIANGLE_NUM], 
//    the three triangles 
//    that are direct neighbors of a given triangle.  TRIANGLE_NEIGHBOR(1,I) 
//    is the index of the triangle which touches side 1, defined by nodes 2 
//    and 3, and so on.  TRIANGLE_NEIGHBOR(1,I) is negative if there is no 
//    neighbor on that side.  In this case, that side of the triangle lies 
//    on the boundary of the triangulation.
//
{
  int *col;
  int i;
  int icol;
  int j;
  int k;
  int side1;
  int side2;
  int tri;
  int triangle_order = 3;
  int tri1;
  int tri2;
  int *triangle_neighbor;

  triangle_neighbor = new int[3*triangle_num];
  col = new int[4*(3*triangle_num)];
//
//  Step 1.
//  From the list of nodes for triangle T, of the form: (I,J,K)
//  construct the three neighbor relations:
//
//    (I,J,1,T) or (J,I,1,T),
//    (J,K,2,T) or (K,J,2,T),
//    (K,I,3,T) or (I,K,3,T)
//
//  where we choose (I,J,1,T) if I < J, or else (J,I,1,T)
//
  for ( tri = 0; tri < triangle_num; tri++ )
  {
    i = triangle_node[0+tri*triangle_order];
    j = triangle_node[1+tri*triangle_order];
    k = triangle_node[2+tri*triangle_order];

    if ( i < j )
    {
      col[0+(3*tri+0)*4] = i;
      col[1+(3*tri+0)*4] = j;
      col[2+(3*tri+0)*4] = 1;
      col[3+(3*tri+0)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+0)*4] = j;
      col[1+(3*tri+0)*4] = i;
      col[2+(3*tri+0)*4] = 1;
      col[3+(3*tri+0)*4] = tri + 1;
    }

    if ( j < k )
    {
      col[0+(3*tri+1)*4] = j;
      col[1+(3*tri+1)*4] = k;
      col[2+(3*tri+1)*4] = 2;
      col[3+(3*tri+1)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+1)*4] = k;
      col[1+(3*tri+1)*4] = j;
      col[2+(3*tri+1)*4] = 2;
      col[3+(3*tri+1)*4] = tri + 1;
    }

    if ( k < i )
    {
      col[0+(3*tri+2)*4] = k;
      col[1+(3*tri+2)*4] = i;
      col[2+(3*tri+2)*4] = 3;
      col[3+(3*tri+2)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+2)*4] = i;
      col[1+(3*tri+2)*4] = k;
      col[2+(3*tri+2)*4] = 3;
      col[3+(3*tri+2)*4] = tri + 1;
    }
  }
//
//  Step 2. Perform an ascending dictionary sort on the neighbor relations.
//  We only intend to sort on rows 1 and 2; the routine we call here
//  sorts on rows 1 through 4 but that won't hurt us.
//
//  What we need is to find cases where two triangles share an edge.
//  Say they share an edge defined by the nodes I and J.  Then there are
//  two columns of COL that start out ( I, J, ?, ? ).  By sorting COL,
//  we make sure that these two columns occur consecutively.  That will
//  make it easy to notice that the triangles are neighbors.
//
  i4col_sort_a ( 4, 3*triangle_num, col );
//
//  Step 3. Neighboring triangles show up as consecutive columns with
//  identical first two entries.  Whenever you spot this happening,
//  make the appropriate entries in TRIANGLE_NEIGHBOR.
//
  for ( j = 0; j < triangle_num; j++ )
  {
    for ( i = 0; i < 3; i++ )
    {
      triangle_neighbor[i+j*3] = -1;
    }
  }

  icol = 1;

  for ( ; ; )
  {
    if ( 3 * triangle_num <= icol )
    {
      break;
    }

    if ( col[0+(icol-1)*4] != col[0+icol*4] || 
         col[1+(icol-1)*4] != col[1+icol*4] )
    {
      icol = icol + 1;
      continue;
    }

    side1 = col[2+(icol-1)*4];
    tri1 =  col[3+(icol-1)*4];
    side2 = col[2+ icol   *4];
    tri2 =  col[3+ icol   *4];

    triangle_neighbor[side1-1+(tri1-1)*3] = tri2;
    triangle_neighbor[side2-1+(tri2-1)*3] = tri1;

    icol = icol + 2;
  }
 
  delete [] col;

  return triangle_neighbor;
}
//****************************************************************************80

int *triangulation_order6_neighbor_triangles ( int triangle_num,
  int triangle_node[] )

//****************************************************************************80
//
//  Purpose:
//
//    TRIANGULATION_ORDER6_NEIGHBOR_TRIANGLES determines triangle neighbors.
//
//  Discussion:
//
//    A triangulation of a set of nodes can be completely described by
//    the coordinates of the nodes, and the list of nodes that make up
//    each triangle.  However, in some cases, it is necessary to know
//    triangle adjacency information, that is, which triangle, if any,
//    is adjacent to a given triangle on a particular side.
//
//    This routine creates a data structure recording this information.
//
//    The primary amount of work occurs in sorting a list of 3 * TRIANGLE_NUM
//    data items.
//
//    This routine was modified to use columns instead of rows.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    01 June 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int TRIANGLE_NUM, the number of triangles.
//
//    Input, int TRIANGLE_NODE[6*TRIANGLE_NUM], the nodes that make up each
//    triangle.
//
//    Output, int TRIANGLE_ORDER6_NEIGHBOR_TRIANGLES[3*TRIANGLE_NUM], 
//    the three triangles 
//    that are direct neighbors of a given triangle.  TRIANGLE_NEIGHBOR(1,I) 
//    is the index of the triangle which touches side 1, defined by nodes 2 
//    and 3, and so on.  TRIANGLE_NEIGHBOR(1,I) is negative if there is no 
//    neighbor on that side.  In this case, that side of the triangle lies 
//    on the boundary of the triangulation.
//
{
  int *col;
  int i;
  int icol;
  int j;
  int k;
  int side1;
  int side2;
  int tri;
  int triangle_order = 6;
  int tri1;
  int tri2;
  int *triangle_neighbor;

  triangle_neighbor = new int[3*triangle_num];
  col = new int[4*(3*triangle_num)];
//
//  Step 1.
//  From the list of nodes for triangle T, of the form: (I,J,K)
//  construct the three neighbor relations:
//
//    (I,J,1,T) or (J,I,1,T),
//    (J,K,2,T) or (K,J,2,T),
//    (K,I,3,T) or (I,K,3,T)
//
//  where we choose (I,J,1,T) if I < J, or else (J,I,1,T)
//
  for ( tri = 0; tri < triangle_num; tri++ )
  {
    i = triangle_node[0+tri*triangle_order];
    j = triangle_node[1+tri*triangle_order];
    k = triangle_node[2+tri*triangle_order];

    if ( i < j )
    {
      col[0+(3*tri+0)*4] = i;
      col[1+(3*tri+0)*4] = j;
      col[2+(3*tri+0)*4] = 1;
      col[3+(3*tri+0)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+0)*4] = j;
      col[1+(3*tri+0)*4] = i;
      col[2+(3*tri+0)*4] = 1;
      col[3+(3*tri+0)*4] = tri + 1;
    }

    if ( j < k )
    {
      col[0+(3*tri+1)*4] = j;
      col[1+(3*tri+1)*4] = k;
      col[2+(3*tri+1)*4] = 2;
      col[3+(3*tri+1)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+1)*4] = k;
      col[1+(3*tri+1)*4] = j;
      col[2+(3*tri+1)*4] = 2;
      col[3+(3*tri+1)*4] = tri + 1;
    }

    if ( k < i )
    {
      col[0+(3*tri+2)*4] = k;
      col[1+(3*tri+2)*4] = i;
      col[2+(3*tri+2)*4] = 3;
      col[3+(3*tri+2)*4] = tri + 1;
    }
    else
    {
      col[0+(3*tri+2)*4] = i;
      col[1+(3*tri+2)*4] = k;
      col[2+(3*tri+2)*4] = 3;
      col[3+(3*tri+2)*4] = tri + 1;
    }
  }
//
//  Step 2. Perform an ascending dictionary sort on the neighbor relations.
//  We only intend to sort on columns 1 and 2; the routine we call here
//  sorts on columns 1 through 4 but that won't hurt us.
//
//  What we need is to find cases where two triangles share an edge.
//  Say they share an edge defined by the nodes I and J.  Then there are
//  two columns of COL that start out ( I, J, ?, ? ).  By sorting COL,
//  we make sure that these two columns occur consecutively.  That will
//  make it easy to notice that the triangles are neighbors.
//
  i4col_sort_a ( 4, 3*triangle_num, col );
//
//  Step 3. Neighboring triangles show up as consecutive columns with
//  identical first two entries.  Whenever you spot this happening,
//  make the appropriate entries in TRIANGLE_NEIGHBOR.
//
  for ( j = 0; j < triangle_num; j++ )
  {
    for ( i = 0; i < 3; i++ )
    {
      triangle_neighbor[i+j*3] = -1;
    }
  }

  icol = 1;

  for ( ; ; )
  {
    if ( 3 * triangle_num <= icol )
    {
      break;
    }

    if ( col[0+(icol-1)*4] != col[0+icol*4] || 
         col[1+(icol-1)*4] != col[1+icol*4] )
    {
      icol = icol + 1;
      continue;
    }

    side1 = col[2+(icol-1)*4];
    tri1 =  col[3+(icol-1)*4];
    side2 = col[2+ icol   *4];
    tri2 =  col[3+ icol   *4];

    triangle_neighbor[side1-1+(tri1-1)*3] = tri2;
    triangle_neighbor[side2-1+(tri2-1)*3] = tri1;

    icol = icol + 2;
  }
 
  delete [] col;

  return triangle_neighbor;
}
//****************************************************************************80

void triangulation_search_delaunay ( int node_num, double node_xy[], int triangle_order,
  int triangle_num, int triangle_node[], int triangle_neighbor[], 
  double p[2], int *triangle, int *edge )

//****************************************************************************80
//
//  Purpose:
//
//    TRIANGULATION_SEARCH_DELAUNAY searches a triangulation for a point.
//
//  Discussion:
//
//    The algorithm "walks" from one triangle to its neighboring triangle,
//    and so on, until a triangle is found containing point P, or P is found 
//    to be outside the convex hull.  
//
//    The algorithm computes the barycentric coordinates of the point with 
//    respect to the current triangle.  If all three quantities are positive,
//    the point is contained in the triangle.  If the I-th coordinate is
//    negative, then (X,Y) lies on the far side of edge I, which is opposite
//    from vertex I.  This gives a hint as to where to search next.
//
//    For a Delaunay triangulation, the search is guaranteed to terminate.
//    For other triangulations, a cycle may occur.
//
//    Note the surprising fact that, even for a Delaunay triangulation of
//    a set of nodes, the nearest point to (X,Y) need not be one of the
//    vertices of the triangle containing (X,Y).  
//
//    The code can be called for triangulations of any order, but only
//    the first three nodes in each triangle are considered.  Thus, if
//    higher order triangles are used, and the extra nodes are intended
//    to give the triangle a polygonal shape, these will have no effect,
//    and the results obtained here might be misleading.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    27 September 2006
//
//  Author:
//
//    Barry Joe,
//    Department of Computing Science,
//    University of Alberta,
//    Edmonton, Alberta, Canada  T6G 2H1
//
//  Reference:
//
//    Barry Joe,
//    GEOMPACK - a software package for the generation of meshes
//    using geometric algorithms,
//    Advances in Engineering Software,
//    Volume 13, pages 325-331, 1991.
//
//  Parameters:
//
//    Input, int NODE_NUM, the number of nodes.
//
//    Input, double NODE_XY[2*NODE_NUM], the coordinates of the nodes.
//
//    Input, int TRIANGLE_ORDER, the order of the triangles.
//
//    Input, int TRIANGLE_NUM, the number of triangles in the triangulation.
//
//    Input, int TRIANGLE_NODE[TRIANGLE_ORDER*TRIANGLE_NUM], 
//    the nodes of each triangle.
//
//    Input, int TRIANGLE_NEIGHBOR[3*TRIANGLE_NUM], the triangle neighbor list.
//
//    Input, double P[2], the coordinates of a point.
//
//    Output, int *TRIANGLE, the index of the triangle where the search ended.
//    If a cycle occurred, then TRIANGLE = -1.
//
//    Output, int *EDGE, indicates the position of the point (X,Y) in
//    triangle TRIANGLE:
//    0, the interior or boundary of the triangle;
//    -1, outside the convex hull of the triangulation, past edge 1;
//    -2, outside the convex hull of the triangulation, past edge 2;
//    -3, outside the convex hull of the triangulation, past edge 3.
//
{
  int a;
  double alpha;
  int b;
  double beta;
  int c;
  int count;
  double det;
  double dxp;
  double dxa;
  double dxb;
  double dyp;
  double dya;
  double dyb;
  double gamma;
  int seed;

  count = 0;
  edge = 0;

  seed = get_seed ( );

  *triangle = i4_uniform ( 1, triangle_num, &seed );

  for ( ; ; )
  {
    count = count + 1;

    if ( triangle_num < count )
    {
      cout << "\n";
      cout << "TRIANGULATION_SEARCH_DELAUNAY - Fatal error!\n";
      cout << "  The algorithm seems to be cycling.\n";
      cout << "  Current triangle is " << *triangle << "\n";
      *triangle = -1;
      *edge = -1;
      return;
    }
//
//  Get the vertices of triangle TRIANGLE.
//
    a = triangle_node[0+(*triangle-1)*triangle_order] - 1;
    b = triangle_node[1+(*triangle-1)*triangle_order] - 1;
    c = triangle_node[2+(*triangle-1)*triangle_order] - 1;
//
//  Using vertex C as a base, compute the distances to vertices A and B,
//  and the point (X,Y).
//
    dxa = node_xy[0+a*2] - node_xy[0+c*2];
    dya = node_xy[1+a*2] - node_xy[1+c*2];

    dxb = node_xy[0+b*2] - node_xy[0+c*2];
    dyb = node_xy[1+b*2] - node_xy[1+c*2];

    dxp = p[0]           - node_xy[0+c*2];
    dyp = p[1]           - node_xy[1+c*2];

    det = dxa * dyb - dya * dxb;
//
//  Compute the barycentric coordinates of the point (X,Y) with respect
//  to this triangle.
//
    alpha = ( dxp * dyb - dyp * dxb ) / det;
    beta =  ( dxa * dyp - dya * dxp ) / det;
    gamma = 1.0 - alpha - beta;
//
//  If the barycentric coordinates are all positive, then the point
//  is inside the triangle and we're done.
//
    if ( 0.0 <= alpha &&
         0.0 <= beta  &&
         0.0 <= gamma )
    {
      break;
    }
//
//  At least one barycentric coordinate is negative.
//
//  If there is a negative barycentric coordinate for which there exists
//  an opposing triangle neighbor closer to the point, move to that triangle.
//
//  (Two coordinates could be negative, in which case we could go for the
//  most negative one, or the most negative one normalized by the actual
//  distance it represents).
//
    if ( alpha < 0.0 && 0 <= triangle_neighbor[1+(*triangle-1)*3] )
    {
      *triangle = triangle_neighbor[1+(*triangle-1)*3];
      continue;
    }
    else if ( beta < 0.0 && 0 <= triangle_neighbor[2+(*triangle-1)*3] )
    {
      *triangle = triangle_neighbor[2+(*triangle-1)*3];
      continue;
    }
    else if ( gamma < 0.0 && 0 <= triangle_neighbor[0+(*triangle-1)*3] )
    {
      *triangle = triangle_neighbor[0+(*triangle-1)*3];
      continue;
    }
//
//  All negative barycentric coordinates correspond to vertices opposite
//  sides on the convex hull.
//
//  Note the edge and exit.
//
    if ( alpha < 0.0 )
    {
      *edge = -2;
      break;
    }
    else if ( beta < 0.0 )
    {
      *edge = -3;
      break;
    }
    else if ( gamma < 0.0 )
    {
      *edge = -1;
      break;
    }
    else
    {
      cout << "\n";
      cout << "TRIANGULATION_SEARCH - Fatal error!\n";
      cout << "  The algorithm seems to have reached a dead end\n";
      cout << "  after " << count << " steps.\n";
      *triangle = -1;
      *edge = -1;
      return;
    }
  }

  return;
}