quadrature_grid_2d.c

一个用来实现偏微分方程中网格的计算库

// $Id: quadrature_grid_2D.C 2788 2008-04-13 02:05:22Z roystgnr $

// The libMesh Finite Element Library.
// Copyright (C) 2002-2007  Benjamin S. Kirk, John W. Peterson
  
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
  
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
  
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



// Local includes
#include "quadrature_grid.h"


void QGrid::init_2D(const ElemType _type,
                    unsigned int)
{
#if DIM > 1
  
  //-----------------------------------------------------------------------
  // 2D quadrature rules

  // We ignore p - the grid rule is just for experimentation

  switch (_type)
    {


      //---------------------------------------------
      // Quadrilateral quadrature rules
    case QUAD4:
    case QUAD8:
    case QUAD9:
      {
	// We compute the 2D quadrature rule as a tensor
	// product of the 1D quadrature rule.
	QGrid q1D(1,_order);
	q1D.init(EDGE2);
	tensor_product_quad( q1D );
	return;
      }

	    
      //---------------------------------------------
      // Triangle quadrature rules
    case TRI3:
    case TRI6:
      {
        _points.resize((_order + 1)*(_order + 2)/2);
        _weights.resize((_order + 1)*(_order + 2)/2);

        unsigned int pt = 0;
        for (int i = 0; i != _order + 1; ++i)
          {
            for (int j = 0; j != _order + 1 - i; ++j)
              {
                _points[pt](0) = (double)i / (double)_order;
                _points[pt](1) = (double)j / (double)_order;
                _weights[pt] = 1.0 / (double)(_order+1) / 
                  (double)(_order+2);
                pt++;
              }
          }
	return;
      }
	    
      //---------------------------------------------
      // Unsupported type
    default:
      {
	std::cerr << "Element type not supported!:" << _type << std::endl;
	libmesh_error();
      }
    }

  libmesh_error();

  return;

#endif
}