element_qoi_derivative.C

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
 
// 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
 
 
 
// General libMesh includes
#include "libmesh/libmesh_common.h"
#include "libmesh/elem.h"
#include "libmesh/fe_base.h"
#include "libmesh/fem_context.h"
#include "libmesh/point.h"
#include "libmesh/quadrature.h"
 
// Local includes
#include "heatsystem.h"
 
// Bring in everything from the libMesh namespace
using namespace libMesh;
 
// We only have one QoI, so we don't bother checking the qois argument
// to see if it was requested from us
void HeatSystem::element_qoi_derivative (DiffContext & context,
                                         const QoISet & /* qois */)
{
  FEMContext & c = cast_ref<FEMContext &>(context);
 
  // First we get some references to cell-specific data that
  // will be used to assemble the linear system.
  FEBase * elem_fe = nullptr;
  c.get_element_fe(0, elem_fe);
 
  // Element Jacobian * quadrature weights for interior integration
  const std::vector<Real> & JxW = elem_fe->get_JxW();
 
  // The basis functions for the element
  const std::vector<std::vector<Real>> & phi = elem_fe->get_phi();
 
  // The number of local degrees of freedom in each variable
  const unsigned int n_T_dofs = c.n_dof_indices(0);
  unsigned int n_qpoints = c.get_element_qrule().n_points();
 
  // Fill the QoI RHS corresponding to this QoI. Since this is the 0th QoI
  // we fill in the [0][i] subderivatives, i corresponding to the variable index.
  // Our system has only one variable, so we only have to fill the [0][0] subderivative
  DenseSubVector<Number> & Q = c.get_qoi_derivatives(0, 0);
 
  // A reference to the system context is built with
  const System & sys = c.get_system();
 
  // Get a pointer to the adjoint solution vector
  NumericVector<Number> & adjoint_solution = const_cast<System &>(sys).get_adjoint_solution(0);
 
  // Get the previous adjoint solution values at all the qps
 
  std::vector<Number> old_adjoint (n_qpoints, 0);
 
  c.interior_values<Number>(0, adjoint_solution, old_adjoint);
 
  // Our QoI depends solely on the final time, so there are no QoI contributions.
  // However, there is a contribution from the adjoint solution timestep, for the
  // time part of the residual of the adjoint problem
  // Loop over the qps
  for (unsigned int qp=0; qp != n_qpoints; qp++)
    for (unsigned int i=0; i != n_T_dofs; i++)
      Q(i) += -JxW[qp] * old_adjoint[qp] * phi[i][qp] * (1./(dynamic_cast<const HeatSystem &>(sys).deltat));
}