QuadLagrangeShape.cpp

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/* *****************************************************************
    MESQUITE -- The Mesh Quality Improvement Toolkit

    Copyright 2006 Lawrence Livermore National Laboratory.  Under
    the terms of Contract B545069 with the University of Wisconsin --
    Madison, Lawrence Livermore National Laboratory retains certain
    rights in this software.

    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
    (lgpl.txt) along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    [email protected]

  ***************************************************************** */
/** \file QuadLagrangeShape.cpp
 *  \author Jason Kraftcheck
 */

#include "QuadLagrangeShape.hpp"
#include "LinearQuadrilateral.hpp"
#include "MsqError.hpp"

namespace MBMesquite
{

EntityTopology QuadLagrangeShape::element_topology() const
{
    return QUADRILATERAL;
}

int QuadLagrangeShape::num_nodes() const
{
    return 9;
}

void QuadLagrangeShape::coefficients( Sample loc,
                                      NodeSet nodeset,
                                      double* coeff_out,
                                      size_t* indices_out,
                                      size_t& num_coeff,
                                      MsqError& err ) const
{
    if( !nodeset.have_any_mid_node() )
    {
        LinearQuadrilateral::coefficients( loc, nodeset, coeff_out, indices_out, num_coeff );
        return;
    }

    switch( loc.dimension )
    {
        case 0:
            num_coeff      = 1;
            indices_out[0] = loc.number;
            coeff_out[0]   = 1.0;
            break;
        case 1:
            coeff_out[0] = coeff_out[1] = coeff_out[2] = coeff_out[3] = coeff_out[4] = coeff_out[5] = coeff_out[6] =
                coeff_out[7] = coeff_out[8] = 0.0;
            if( nodeset.mid_edge_node( loc.number ) )
            {
                // if mid-edge node is present
                num_coeff      = 1;
                indices_out[0] = loc.number + 4;
                coeff_out[0]   = 1.0;
            }
            else
            {
                // If mid-edge node is not present, mapping function value
                // for linear edge is even weight of adjacent vertices.
                num_coeff      = 2;
                indices_out[0] = loc.number;
                indices_out[1] = ( loc.number + 1 ) % 4;
                coeff_out[0]   = 0.5;
                coeff_out[1]   = 0.5;
            }
            break;
        case 2:
            if( nodeset.mid_face_node( 0 ) )
            {  // if quad center node is present
                num_coeff      = 1;
                indices_out[0] = 8;
                coeff_out[0]   = 1.0;
            }
            else
            {
                // for linear element, (no mid-edge nodes), all corners contribute 1/4.
                num_coeff      = 4;
                indices_out[0] = 0;
                indices_out[1] = 1;
                indices_out[2] = 2;
                indices_out[3] = 3;
                coeff_out[0]   = 0.25;
                coeff_out[1]   = 0.25;
                coeff_out[2]   = 0.25;
                coeff_out[3]   = 0.25;
                // add in contribution for any mid-edge nodes present
                for( int i = 0; i < 4; ++i )
                {  // for each edge
                    if( nodeset.mid_edge_node( i ) )
                    {
                        indices_out[num_coeff] = i + 4;
                        coeff_out[num_coeff]   = 0.5;
                        coeff_out[i] -= 0.25;
                        coeff_out[( i + 1 ) % 4] -= 0.25;
                        ++num_coeff;
                    }
                }
            }
            break;
        default:
            MSQ_SETERR( err )
            ( MsqError::UNSUPPORTED_ELEMENT,
              "Request for dimension %d mapping function value"
              "for a quadrilateral element",
              loc.dimension );
    }
}

static void derivatives_at_corner( unsigned corner,
                                   NodeSet nodeset,
                                   size_t* vertices,
                                   MsqVector< 2 >* derivs,
                                   size_t& num_vtx )
{
    static const unsigned xi_adj_corners[]  = { 1, 0, 3, 2 };
    static const unsigned xi_adj_edges[]    = { 0, 0, 2, 2 };
    static const unsigned eta_adj_corners[] = { 3, 2, 1, 0 };
    static const unsigned eta_adj_edges[]   = { 3, 1, 1, 3 };

    static const double corner_xi[]  = { -1, 1, 1, -1 };  // xi values by corner
    static const double corner_eta[] = { -1, -1, 1, 1 };  // eta values by corner
    static const double other_xi[]   = { 1, -1, -1, 1 };  // xi values for adjacent corner in xi direction
    static const double other_eta[]  = { 1, 1, -1, -1 };  // eta values for adjcent corner in eta direction
    static const double mid_xi[]     = { 2, -2, -2, 2 };  // xi values for mid-node in xi direction
    static const double mid_eta[]    = { 2, 2, -2, -2 };  // eta values for mid-node in eta direction

    num_vtx     = 3;
    vertices[0] = corner;
    vertices[1] = xi_adj_corners[corner];
    vertices[2] = eta_adj_corners[corner];

    derivs[0][0] = corner_xi[corner];
    derivs[0][1] = corner_eta[corner];
    derivs[1][0] = other_xi[corner];
    derivs[1][1] = 0.0;
    derivs[2][0] = 0.0;
    derivs[2][1] = other_eta[corner];

    if( nodeset.mid_edge_node( xi_adj_edges[corner] ) )
    {
        vertices[num_vtx]  = 4 + xi_adj_edges[corner];
        derivs[num_vtx][0] = 2.0 * mid_xi[corner];
        derivs[num_vtx][1] = 0.0;
        derivs[0][0] -= mid_xi[corner];
        derivs[1][0] -= mid_xi[corner];
        ++num_vtx;
    }

    if( nodeset.mid_edge_node( eta_adj_edges[corner] ) )
    {
        vertices[num_vtx]  = 4 + eta_adj_edges[corner];
        derivs[num_vtx][0] = 0.0;
        derivs[num_vtx][1] = 2.0 * mid_eta[corner];
        derivs[0][1] -= mid_eta[corner];
        derivs[2][1] -= mid_eta[corner];
        ++num_vtx;
    }
}

static void derivatives_at_mid_edge( unsigned edge,
                                     NodeSet nodeset,
                                     size_t* vertices,
                                     MsqVector< 2 >* derivs,
                                     size_t& num_vtx )
{
    static const double values[][9]      = { { -0.5, -0.5, 0.5, 0.5, -1.0, 2.0, 1.0, 2.0, 4.0 },
                                        { -0.5, 0.5, 0.5, -0.5, -2.0, 1.0, -2.0, -1.0, -4.0 },
                                        { -0.5, -0.5, 0.5, 0.5, -1.0, -2.0, 1.0, -2.0, -4.0 },
                                        { -0.5, 0.5, 0.5, -0.5, 2.0, 1.0, 2.0, -1.0, 4.0 } };
    static const double edge_values[][2] = { { -1, 1 }, { -1, 1 }, { 1, -1 }, { 1, -1 } };
    const unsigned prev_corner           = edge;              // index of start vertex of edge
    const unsigned next_corner           = ( edge + 1 ) % 4;  // index of end vertex of edge
    const unsigned is_eta_edge           = edge % 2;          // edge is xi = +/- 0
    const unsigned is_xi_edge            = 1 - is_eta_edge;   // edge is eta = +/- 0
    // const unsigned mid_edge_node = edge + 4;     // mid-edge node index
    const unsigned prev_opposite = ( prev_corner + 3 ) % 4;  // index of corner adjacent to prev_corner
    const unsigned next_opposite = ( next_corner + 1 ) % 4;  // index of corner adjacent to next_corner;

    // First do derivatives along edge (e.g. wrt xi if edge is eta = +/-1)
    num_vtx                = 2;
    vertices[0]            = prev_corner;
    vertices[1]            = next_corner;
    derivs[0][is_eta_edge] = edge_values[edge][0];
    derivs[0][is_xi_edge]  = 0.0;
    derivs[1][is_eta_edge] = edge_values[edge][1];
    derivs[1][is_xi_edge]  = 0.0;
    // That's it for the edge-direction derivatives.  No other vertices contribute.

    // Next handle the linear element case.  Handle this as a special case first,
    // so the generalized solution doesn't impact performance for linear elements
    // too much.
    if( !nodeset.have_any_mid_node() )
    {
        num_vtx                = 4;
        vertices[2]            = prev_opposite;
        vertices[3]            = next_opposite;
        derivs[0][is_xi_edge]  = values[edge][prev_corner];
        derivs[1][is_xi_edge]  = values[edge][next_corner];
        derivs[2][is_xi_edge]  = values[edge][prev_opposite];
        derivs[2][is_eta_edge] = 0.0;
        derivs[3][is_xi_edge]  = values[edge][next_opposite];
        derivs[3][is_eta_edge] = 0.0;
        return;
    }

    // Initial (linear) contribution for each corner
    double v[4] = { values[edge][0], values[edge][1], values[edge][2], values[edge][3] };

    // If mid-face node is present
    double v8 = 0.0;
    if( nodeset.mid_face_node( 0 ) )
    {
        v8                           = values[edge][8];
        vertices[num_vtx]            = 8;
        derivs[num_vtx][is_eta_edge] = 0.0;
        derivs[num_vtx][is_xi_edge]  = v8;
        v[0] -= 0.25 * v8;
        v[1] -= 0.25 * v8;
        v[2] -= 0.25 * v8;
        v[3] -= 0.25 * v8;
        ++num_vtx;
    }

    // If mid-edge nodes are present
    for( unsigned i = 0; i < 4; ++i )
    {
        if( nodeset.mid_edge_node( i ) )
        {
            const double value = values[edge][i + 4] - 0.5 * v8;
            if( fabs( value ) > 0.125 )
            {
                v[i] -= 0.5 * value;
                v[( i + 1 ) % 4] -= 0.5 * value;
                vertices[num_vtx]            = i + 4;
                derivs[num_vtx][is_eta_edge] = 0.0;
                derivs[num_vtx][is_xi_edge]  = value;
                ++num_vtx;
            }
        }
    }

    // update values for adjacent corners
    derivs[0][is_xi_edge] = v[prev_corner];
    derivs[1][is_xi_edge] = v[next_corner];
    // do other two corners
    if( fabs( v[prev_opposite] ) > 0.125 )
    {
        vertices[num_vtx]            = prev_opposite;
        derivs[num_vtx][is_eta_edge] = 0.0;
        derivs[num_vtx][is_xi_edge]  = v[prev_opposite];
        ++num_vtx;
    }
    if( fabs( v[next_opposite] ) > 0.125 )
    {
        vertices[num_vtx]            = next_opposite;
        derivs[num_vtx][is_eta_edge] = 0.0;
        derivs[num_vtx][is_xi_edge]  = v[next_opposite];
        ++num_vtx;
    }
}

static void derivatives_at_mid_elem( NodeSet nodeset, size_t* vertices, MsqVector< 2 >* derivs, size_t& num_vtx )
{
    // fast linear case
    // This is provided as an optimization for linear elements.
    // If this block of code were removed, the general-case code
    // below should produce the same result.
    if( !nodeset.have_any_mid_node() )
    {
        num_vtx      = 4;
        vertices[0]  = 0;
        derivs[0][0] = -0.5;
        derivs[0][1] = -0.5;
        vertices[1]  = 1;
        derivs[1][0] = 0.5;
        derivs[1][1] = -0.5;
        vertices[2]  = 2;
        derivs[2][0] = 0.5;
        derivs[2][1] = 0.5;
        vertices[3]  = 3;
        derivs[3][0] = -0.5;
        derivs[3][1] = 0.5;
        return;
    }

    num_vtx = 0;

    // N_0
    if( !nodeset.both_edge_nodes( 0, 3 ) )
    {  // if eiter adjacent mid-edge node is missing
        vertices[num_vtx]  = 0;
        derivs[num_vtx][0] = nodeset.mid_edge_node( 3 ) ? 0.0 : -0.5;
        derivs[num_vtx][1] = nodeset.mid_edge_node( 0 ) ? 0.0 : -0.5;
        ++num_vtx;
    }

    // N_1
    if( !nodeset.both_edge_nodes( 0, 1 ) )
    {  // if eiter adjacent mid-edge node is missing
        vertices[num_vtx]  = 1;
        derivs[num_vtx][0] = nodeset.mid_edge_node( 1 ) ? 0.0 : 0.5;
        derivs[num_vtx][1] = nodeset.mid_edge_node( 0 ) ? 0.0 : -0.5;
        ++num_vtx;
    }

    // N_2
    if( !nodeset.both_edge_nodes( 1, 2 ) )
    {  // if eiter adjacent mid-edge node is missing
        vertices[num_vtx]  = 2;
        derivs[num_vtx][0] = nodeset.mid_edge_node( 1 ) ? 0.0 : 0.5;
        derivs[num_vtx][1] = nodeset.mid_edge_node( 2 ) ? 0.0 : 0.5;
        ++num_vtx;
    }

    // N_3
    if( !nodeset.both_edge_nodes( 2, 3 ) )
    {  // if eiter adjacent mid-edge node is missing
        vertices[num_vtx]  = 3;
        derivs[num_vtx][0] = nodeset.mid_edge_node( 3 ) ? 0.0 : -0.5;
        derivs[num_vtx][1] = nodeset.mid_edge_node( 2 ) ? 0.0 : 0.5;
        ++num_vtx;
    }

    // N_4
    if( nodeset.mid_edge_node( 0 ) )
    {
        vertices[num_vtx]  = 4;
        derivs[num_vtx][0] = 0.0;
        derivs[num_vtx][1] = -1.0;
        ++num_vtx;
    }

    // N_5
    if( nodeset.mid_edge_node( 1 ) )
    {
        vertices[num_vtx]  = 5;
        derivs[num_vtx][0] = 1.0;
        derivs[num_vtx][1] = 0.0;
        ++num_vtx;
    }

    // N_6
    if( nodeset.mid_edge_node( 2 ) )
    {
        vertices[num_vtx]  = 6;
        derivs[num_vtx][0] = 0.0;
        derivs[num_vtx][1] = 1.0;
        ++num_vtx;
    }

    // N_7
    if( nodeset.mid_edge_node( 3 ) )
    {
        vertices[num_vtx]  = 7;
        derivs[num_vtx][0] = -1.0;
        derivs[num_vtx][1] = 0.0;
        ++num_vtx;
    }

    // N_8 (mid-quad node) never contributes to Jacobian at element center!!!
}

void QuadLagrangeShape::derivatives( Sample loc,
                                     NodeSet nodeset,
                                     size_t* vertex_indices_out,
                                     MsqVector< 2 >* d_coeff_d_xi_out,
                                     size_t& num_vtx,
                                     MsqError& err ) const
{
    if( !nodeset.have_any_mid_node() )
    {
        LinearQuadrilateral::derivatives( loc, nodeset, vertex_indices_out, d_coeff_d_xi_out, num_vtx );
        return;
    }

    switch( loc.dimension )
    {
        case 0:
            derivatives_at_corner( loc.number, nodeset, vertex_indices_out, d_coeff_d_xi_out, num_vtx );
            break;
        case 1:
            derivatives_at_mid_edge( loc.number, nodeset, vertex_indices_out, d_coeff_d_xi_out, num_vtx );
            break;
        case 2:
            derivatives_at_mid_elem( nodeset, vertex_indices_out, d_coeff_d_xi_out, num_vtx );
            break;
        default:
            MSQ_SETERR( err )( "Invalid/unsupported logical dimension", MsqError::INVALID_ARG );
    }
}

void QuadLagrangeShape::ideal( Sample, MsqMatrix< 3, 2 >& J, MsqError& ) const
{
    J( 0, 0 ) = J( 1, 1 ) = 1.0;
    J( 0, 1 ) = J( 1, 0 ) = 0.0;
    J( 2, 0 ) = J( 2, 1 ) = 0.0;
}

}  // namespace MBMesquite