function triangulation_rcm ( input_node_filename, input_triangulation_filename )

%% MAIN is the main program for TRIANGULATION_RCM.
%
%  Discussion:
%
%    TRIANGULATION_RCM applies the RCM reordering to a triangulation.
%
%    The user supplies a node file and a triangle file, containing
%    the coordinates of the nodes, and the indices of the nodes that
%    make up each triangle.  Either 3-node or 6-node triangles may
%    be used.
%
%    The program reads the data, computes the adjacency information,
%    carries out the RCM algorithm to get the permutation, applies
%    the permutation to the nodes and triangles, and writes out
%    new node and triangle files that correspond to the RCM permutation.
%
%    Note that node data is normally two dimensional, that is,
%    each node has an X and Y coordinate.  In some applications, it
%    may be desirable to specify more information.  This program
%    will accept node data that includes DIM_NUM entries on each line,
%    as long as DIM_NUM is the same for each entry.  
%
%  Modified:
%
%    08 January 2007
%
%  Author:
%
%    John Burkardt
%
%  Usage:
%
%    triangulation_rcm ( 'node_file', 'triangulation_file' )
%
  timestamp;

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_RCM\n' );
  fprintf ( 1, '  MATLAB version\n' );
  fprintf ( 1, '  Read a node dataset of NODE_NUM points in 2 dimensions.\n' );
  fprintf ( 1, '  Read an associated triangulation dataset of TRIANGLE_NUM\n' );
  fprintf ( 1, '  triangles using 3 or 6 nodes.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Apply the RCM reordering (Reverse Cuthill-McKee).\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Reorder the data and write it out to files.\n' );
%
%  Get the number of command line arguments.
%
  if ( nargin < 1 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_RCM:\n' );
    input_node_filename = input ( ...
      '  Please enter the name of the node file.' );

  end

  if ( nargin < 2 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_RCM:\n' );
    input_triangulation_filename = input ( ...
      '  Please enter the name of the triangulation file.' );

  end
%
%  Read the node data.
%
  [ dim_num, node_num ] = dtable_header_read ( ...
    input_node_filename );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of ""%s".\n', input_node_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Spatial dimension DIM_NUM = %d\n', dim_num );
  fprintf ( 1, '  Number of nodes NODE_NUM  = %d\n', node_num );

  node_xy(1:dim_num,1:node_num) = dtable_data_read ( ...
    input_node_filename, dim_num, node_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in ""%s".\n', input_node_filename );

  r8mat_transpose_print_some ( dim_num, node_num, node_xy, ...
    1, 1, dim_num, 5, '  Coordinates of first 5 nodes:' );
%
%  Read the triangulation data.
%
  [ triangle_order, triangle_num ] = itable_header_read ( ...
    input_triangulation_filename );

  if ( triangle_order ~= 3 & triangle_order ~= 6 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_RCM - Fatal error!\n' );
    fprintf ( 1, '  Data is not for a 3-node or 6-node triangulation.\n' );
    error ( 'TRIANGULATION_RCM - Fatal error!' );
  end

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of ""%s".\n', input_triangulation_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Triangle order = %d\n', triangle_order );
  fprintf ( 1, '  Number of triangles TRIANGLE_NUM  = %d\n', triangle_num );

  triangle_node(1:triangle_order,1:triangle_num) = itable_data_read ( ...
    input_triangulation_filename, triangle_order, triangle_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in ""%s".\n', input_triangulation_filename );

  i4mat_transpose_print_some ( triangle_order, triangle_num, triangle_node, ...
    1, 1, triangle_order, 5, '  First five triangles:' );

  if ( triangle_order == 3 )
%
%  Create the triangle neighbor array.
%
    triangle_neighbor = triangulation_order3_neighbor_triangles ( triangle_num, ...
      triangle_node );
%
%  Count the number of adjacencies, and set up the ADJ_ROW 
%  adjacency pointer array.
%
    [ adj_num, adj_row ] = triangulation_order3_adj_count ( node_num, ...
      triangle_num, triangle_node, triangle_neighbor );
%
%  Set up the ADJ adjacency array.
%
    adj = triangulation_order3_adj_set ( node_num, triangle_num, triangle_node, ...
      triangle_neighbor, adj_num, adj_row );

  elseif ( triangle_order == 6 )
%
%  Create the triangle neighbor array.
%
    triangle_neighbor = triangulation_order6_neighbor_triangles ( triangle_num, ...
      triangle_node );
%
%  Count the number of adjacencies, and set up the ADJ_ROW 
%  adjacency pointer array.
%
    [ adj_num, adj_row ] = triangulation_order6_adj_count ( node_num, ...
      triangle_num, triangle_node, triangle_neighbor );
%
%  Set up the ADJ adjacency array.
%
    adj = triangulation_order6_adj_set ( node_num, triangle_num, triangle_node, ...
      triangle_neighbor, adj_num, adj_row );

  end

  bandwidth = adj_bandwidth ( node_num, adj_num, adj_row, adj );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  ADJ bandwidth = %d\n', bandwidth );
%
%  Compute the RCM permutation.
%
  perm = genrcm ( node_num, adj_num, adj_row, adj );

  perm_inv = perm_inverse3 ( node_num, perm );

  bandwidth = adj_perm_bandwidth ( node_num, adj_num, adj_row, adj, ...
    perm, perm_inv );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Permuted ADJ bandwidth = %d\n', bandwidth );
%
%  Permute the nodes according to the permutation vector.
%
  node_xy = r8col_permute ( dim_num, node_num, node_xy, perm );
%
%  Permute the node indices in the triangle array.
%
  for i = 1 : triangle_order
    for j = 1 : triangle_num
      node = triangle_node(i,j);
      triangle_node(i,j) = perm_inv ( node );
    end
  end
%
%  Create the output file names from the input file names.
%
  output_node_filename = file_name_ext_swap ( ...
    input_node_filename, 'rcm.txt' );

  output_triangulation_filename = file_name_ext_swap ( ...
    input_triangulation_filename, 'rcm.txt' );
%
%  Write out the node and triangle data for the quadratic mesh
%
  header = 1;

  dtable_write ( output_node_filename, dim_num, ...
    node_num, node_xy, header );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Created the node file "%s".\n', output_node_filename );

  itable_write ( output_triangulation_filename, triangle_order, ...
    triangle_num, triangle_node, header );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Created the triangulation file "%s".\n', ...
    output_triangulation_filename );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_RCM\n' );
  fprintf ( 1, '  Normal end of execution.\n' );

  fprintf ( 1, '\n' );
  timestamp;