MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType > Class Template Reference

#include <deal.II/matrix_free/operators.h>

Public Member Functions
	CellwiseInverseMassMatrix (const FEEvaluationBase< dim, n_components, Number, false, VectorizedArrayType > &fe_eval)
void	apply (const AlignedVector< VectorizedArrayType > &inverse_coefficient, const unsigned int n_actual_components, const VectorizedArrayType *in_array, VectorizedArrayType *out_array) const
void	apply (const VectorizedArrayType *in_array, VectorizedArrayType *out_array) const
void	transform_from_q_points_to_basis (const unsigned int n_actual_components, const VectorizedArrayType *in_array, VectorizedArrayType *out_array) const
void	fill_inverse_JxW_values (AlignedVector< VectorizedArrayType > &inverse_jxw) const

Private Attributes
const FEEvaluationBase< dim, n_components, Number, false, VectorizedArrayType > &	fe_eval

Detailed Description

template<int dim, int fe_degree, int n_components = 1, typename Number = double, typename VectorizedArrayType = VectorizedArray<Number>>
class MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >

This class implements the operation of the action of the inverse of a mass matrix on an element for the special case of an evaluation object with as many quadrature points as there are cell degrees of freedom. It uses algorithms from FEEvaluation and produces the exact mass matrix for DGQ elements. This algorithm uses tensor products of inverse 1D shape matrices over quadrature points, so the inverse operation is exactly as expensive as applying the forward operator on each cell. Of course, for continuous finite elements this operation does not produce the inverse of a mass operation as the coupling between the elements cannot be considered by this operation.

The equation may contain variable coefficients, so the user is required to provide an array for the inverse of the local coefficient (this class provide a helper method 'fill_inverse_JxW_values' to get the inverse of a constant-coefficient operator).

Author

Martin Kronbichler, 2014

Definition at line 624 of file operators.h.

Constructor & Destructor Documentation

CellwiseInverseMassMatrix()

template<int dim, int fe_degree, int n_components, typename Number , typename VectorizedArrayType >

MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::CellwiseInverseMassMatrix ( const FEEvaluationBase< dim, n_components, Number, false, VectorizedArrayType > &  fe_eval )

inline

Constructor. Initializes the shape information from the ShapeInfo field in the class FEEval.

Definition at line 972 of file operators.h.

Member Function Documentation

apply() [1/2]

template<int dim, int fe_degree, int n_components, typename Number , typename VectorizedArrayType >

void MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::apply ( const AlignedVector< VectorizedArrayType > &  inverse_coefficient, const unsigned int  n_actual_components, const VectorizedArrayType *  in_array, VectorizedArrayType *  out_array  ) const

inline

Applies the inverse mass matrix operation on an input array. It is assumed that the passed input and output arrays are of correct size, namely FEEvaluation::dofs_per_cell long. The inverse of the local coefficient (also containing the inverse JxW values) must be passed as first argument. Passing more than one component in the coefficient is allowed.

Definition at line 1050 of file operators.h.

apply() [2/2]

template<int dim, int fe_degree, int n_components, typename Number , typename VectorizedArrayType >

void MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::apply ( const VectorizedArrayType *  in_array, VectorizedArrayType *  out_array  ) const

inline

Applies the inverse mass matrix operation on an input array, using the inverse of the JxW values provided by the fe_eval argument passed to the constructor of this class. Note that the user code must call FEEvaluation::reinit() on the underlying evaluator to make the FEEvaluationBase::JxW() method return the information of the correct cell. It is assumed that the pointers of the input and output arrays are valid over the length FEEvaluation::dofs_per_cell, which is the number of entries processed by this function. The in_array and out_array arguments may point to the same memory position.

Definition at line 1027 of file operators.h.

transform_from_q_points_to_basis()

template<int dim, int fe_degree, int n_components, typename Number , typename VectorizedArrayType >

void MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::transform_from_q_points_to_basis ( const unsigned int  n_actual_components, const VectorizedArrayType *  in_array, VectorizedArrayType *  out_array  ) const

inline

This operation performs a projection from the data given in quadrature points to the actual basis underlying this object. This projection can also be interpreted as a change of the basis from the Lagrange interpolation polynomials in the quadrature points to the basis underlying the current fe_eval object.

Calling this function on an array as

inverse_mass.transform_from_q_points_to_basis(1, array,
                                              phi.begin_dof_values());

is equivalent to

for (unsigned int q=0; q<phi.n_q_points; ++q)
  phi.submit_value(array[q], q);
phi.integrate(true, false);
inverse_mass.apply(coefficients, 1, phi.begin_dof_values(),
                   phi.begin_dof_values());

provided that coefficients holds the inverse of the quadrature weights and no additional coefficients. This setup highlights the underlying projection, testing a right hand side and applying an inverse mass matrix. This function works both for the scalar case as described in the example or for multiple components that are laid out component by component.

Compared to the more verbose alternative, the given procedure is considerably faster because it can bypass the integrate() step and the first half of the transformation to the quadrature points, reducing the number of tensor product calls from 3*dim*n_components to dim*n_components.

Definition at line 1079 of file operators.h.

fill_inverse_JxW_values()

template<int dim, int fe_degree, int n_components, typename Number , typename VectorizedArrayType >

void MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::fill_inverse_JxW_values ( AlignedVector< VectorizedArrayType > &  inverse_jxw ) const

inline

Fills the given array with the inverse of the JxW values, i.e., a mass matrix with coefficient 1. Non-unit coefficients must be multiplied (in inverse form) to this array.

Definition at line 994 of file operators.h.

Member Data Documentation

fe_eval

template<int dim, int fe_degree, int n_components = 1, typename Number = double, typename VectorizedArrayType = VectorizedArray<Number>>

const FEEvaluationBase<dim, n_components, Number, false, VectorizedArrayType>& MatrixFreeOperators::CellwiseInverseMassMatrix< dim, fe_degree, n_components, Number, VectorizedArrayType >::fe_eval

private

A reference to the FEEvaluation object for getting the JxW_values.

Definition at line 726 of file operators.h.

---

The documentation for this class was generated from the following file:

• include/deal.II/matrix_free/operators.h