Represents a mathematical expression evaluated at a pre-defined set of points on the reference cell. More...

#include <Expression.h>

Public Types
using	scalar_type = T
	Scalar type.

using	geometry_type = U
	Geometry type of the points.

Public Member Functions
	Expression (const std::vector< std::shared_ptr< const Function< scalar_type, geometry_type > > > &coefficients, const std::vector< std::shared_ptr< const Constant< scalar_type > > > &constants, std::span< const geometry_type > X, std::array< std::size_t, 2 > Xshape, std::function< void(scalar_type , const scalar_type , const scalar_type , const geometry_type , const int , const uint8_t )> fn, const std::vector< int > &value_shape, std::shared_ptr< const FunctionSpace< geometry_type > > argument_function_space=nullptr)
	Create an Expression.

	Expression (Expression &&e)=default
	Move constructor.

virtual	~Expression ()=default
	Destructor.

std::shared_ptr< const FunctionSpace< geometry_type > >	argument_function_space () const
	Get argument function space.

const std::vector< std::shared_ptr< const Function< scalar_type, geometry_type > > > &	coefficients () const
	Get coefficients.

const std::vector< std::shared_ptr< const Constant< scalar_type > > > &	constants () const
	Get constants.

std::vector< int >	coefficient_offsets () const
	Offset for each coefficient expansion array on a cell.

void	eval (const mesh::Mesh< geometry_type > &mesh, std::span< const std::int32_t > entities, std::span< scalar_type > values, std::array< std::size_t, 2 > vshape) const
	Evaluate Expression on cells or facets.

const std::function< void(scalar_type , const scalar_type , const scalar_type , const geometry_type , const int , const uint8_t )> &	get_tabulate_expression () const
	Get function for tabulate_expression.

int	value_size () const
	Get value size.

const std::vector< int > &	value_shape () const
	Get value shape.

std::pair< std::vector< geometry_type >, std::array< std::size_t, 2 > >	X () const
	Evaluation points on the reference cell.

Detailed Description

template<dolfinx::scalar T, std::floating_point U>
class dolfinx::fem::Expression< T, U >

Represents a mathematical expression evaluated at a pre-defined set of points on the reference cell.

This class closely follows the concept of a UFC Expression.

The functionality can be used to evaluate a gradient of a Function at quadrature points in all cells. This evaluated gradient can then be used as input in to a non-FEniCS function that calculates a material constitutive model.

Template Parameters

T	The scalar type
U	The mesh geometry scalar type

Member Typedef Documentation

◆ scalar_type

template<dolfinx::scalar T, std::floating_point U>

using scalar_type = T

Scalar type.

Field type for the Expression, e.g. double, std::complex<float>, etc.

Constructor & Destructor Documentation

◆ Expression()

template<dolfinx::scalar T, std::floating_point U>

Expression	(	const std::vector< std::shared_ptr< const Function< scalar_type, geometry_type > > > &	coefficients,
		const std::vector< std::shared_ptr< const Constant< scalar_type > > > &	constants,
		std::span< const geometry_type >	X,
		std::array< std::size_t, 2 >	Xshape,
		std::function< void(scalar_type , const scalar_type , const scalar_type , const geometry_type , const int , const uint8_t )>	fn,
		const std::vector< int > &	value_shape,
		std::shared_ptr< const FunctionSpace< geometry_type > >	argument_function_space = nullptr )

inline

Create an Expression.

Note: Users should prefer the create_expression factory functions.

Parameters

[in]	coefficients	Coefficients in the Expression.
[in]	constants	Constants in the Expression
[in]	X	Points on the reference cell, `shape=(number of / points, tdim)` and storage is row-major.
[in]	Xshape	Shape of `X`.
[in]	fn	Function for tabulating the Expression.
[in]	value_shape	Shape of Expression evaluated at single point.
[in]	argument_function_space	Function space for Argument.

Member Function Documentation

◆ argument_function_space()

template<dolfinx::scalar T, std::floating_point U>

std::shared_ptr< const FunctionSpace< geometry_type > > argument_function_space ( ) const

inline

Get argument function space.

Returns: The argument function space, nullptr if there is no argument.

◆ coefficient_offsets()

template<dolfinx::scalar T, std::floating_point U>

std::vector< int > coefficient_offsets ( ) const

inline

Offset for each coefficient expansion array on a cell.

Used to pack data for multiple coefficients in a flat array. The last entry is the size required to store all coefficients.

Returns: The offsets.

◆ coefficients()

template<dolfinx::scalar T, std::floating_point U>

const std::vector< std::shared_ptr< const Function< scalar_type, geometry_type > > > & coefficients ( ) const

inline

Get coefficients.

Returns: Vector of attached coefficients.

◆ constants()

template<dolfinx::scalar T, std::floating_point U>

const std::vector< std::shared_ptr< const Constant< scalar_type > > > & constants ( ) const

inline

Get constants.

Returns: Vector of attached constants with their names. Names are used to set constants in user's c++ code. Index in the vector is the position of the constant in the original (nonsimplified) form.

◆ eval()

template<dolfinx::scalar T, std::floating_point U>

void eval	(	const mesh::Mesh< geometry_type > &	mesh,
		std::span< const std::int32_t >	entities,
		std::span< scalar_type >	values,
		std::array< std::size_t, 2 >	vshape ) const

inline

Evaluate Expression on cells or facets.

Parameters

[in]	mesh	Cells on which to evaluate the Expression.
[in]	entities	List of entities to evaluate the expression on. This could be either a list of cells or a list of (cell, local
[out]	values	A 2D array to store the result. Caller is responsible for correct sizing which should be `(num_cells, / num_points * value_size * num_all_argument_dofs columns)`. facet index) tuples. Array is flattened per entity.
[in]	vshape	The shape of `values` (row-major storage).

◆ get_tabulate_expression()

template<dolfinx::scalar T, std::floating_point U>

const std::function< void(scalar_type *, const scalar_type *, const scalar_type *, const geometry_type *, const int *, const uint8_t *)> & get_tabulate_expression ( ) const

inline

Get function for tabulate_expression.

Returns: fn Function to tabulate expression.

◆ value_shape()

template<dolfinx::scalar T, std::floating_point U>

const std::vector< int > & value_shape ( ) const

inline

Get value shape.

Returns: The value shape.

◆ value_size()

template<dolfinx::scalar T, std::floating_point U>

int value_size ( ) const

inline

Get value size.

Returns: The value size.

◆ X()

template<dolfinx::scalar T, std::floating_point U>

std::pair< std::vector< geometry_type >, std::array< std::size_t, 2 > > X ( ) const

inline

Evaluation points on the reference cell.

Returns: Evaluation points.

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

/__w/dolfinx/dolfinx/cpp/dolfinx/fem/Expression.h
/__w/dolfinx/dolfinx/cpp/dolfinx/fem/Function.h

Public Types

Public Member Functions

Detailed Description

Member Typedef Documentation

◆ scalar_type

Constructor & Destructor Documentation

◆ Expression()

Member Function Documentation

◆ argument_function_space()

◆ coefficient_offsets()

◆ coefficients()

◆ constants()

◆ eval()

◆ get_tabulate_expression()

◆ value_shape()

◆ value_size()

◆ X()