Expression< T, U > Class Template Reference

An Expression represents a mathematical expression evaluated at a pre-defined points on a 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 *, void *)> fn, const std::vector< std::size_t > &value_shape, std::shared_ptr< const FunctionSpace< geometry_type > > argument_space=nullptr)
	Create an Expression.
	Expression (Expression &&e)=default
	Move constructor.
virtual	~Expression ()=default
	Destructor.
std::shared_ptr< const FunctionSpace< geometry_type > >	argument_space () const
	Argument function space.
const std::vector< std::shared_ptr< const Function< scalar_type, geometry_type > > > &	coefficients () const
	Expression coefficients.
const std::vector< std::shared_ptr< const Constant< scalar_type > > > &	constants () const
	Expression constants.
std::vector< int >	coefficient_offsets () const
	Offset for each coefficient expansion array on a cell.
const std::function< void(scalar_type *, const scalar_type *, const scalar_type *, const geometry_type *, const int *, const uint8_t *, void *)> &	kernel () const
	Function for tabulating the Expression.
int	value_size () const
	Value size of the Expression result.
const std::vector< std::size_t > &	value_shape () const
	Value shape of of Expression result (at a point),.
std::pair< std::vector< geometry_type >, std::array< std::size_t, 2 > >	X () const
	Evaluation point coordinates on the reference cell.

Detailed Description

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

An Expression represents a mathematical expression evaluated at a pre-defined points on a reference cell.

An Expression can be evaluated using tabulate_expression.

An example of Expression use is to evaluate the gradient of a Function at quadrature points in cells. The evaluated gradient can then be used as input in to a non-FEniCS function that evaluates 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 = dolfinx::scalar_value_t<T>>

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 = dolfinx::scalar_value_t<T>>

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 *, void *)> fn, const std::vector< std::size_t > & value_shape, std::shared_ptr< const FunctionSpace< geometry_type > > argument_space = nullptr )

inline

Create an Expression.

Note

Users should prefer the fem::create_expression factory functions for creating an Expression.

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_space	Function space for Argument. Used to computed a 1-form expression, e.g. can be used to create a matrix that when applied to a degree-of-freedom vector gives the expression values at the evaluation points.

Member Function Documentation

argument_space()

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

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

inline

Argument function space.

Returns

Argument function space, nullptr if there is no argument.

coefficient_offsets()

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

std::vector< int > coefficient_offsets ( ) const

inline

Offset for each coefficient expansion array on a cell.

Used to pack data for multiple coefficients into 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 = dolfinx::scalar_value_t<T>>

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

inline

Expression coefficients.

Returns

List of attached coefficients.

constants()

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

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

inline

Expression constants.

Returns

List of attached constants.

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

• /__w/dolfinx/dolfinx/cpp/dolfinx/fem/assembler.h
• /__w/dolfinx/dolfinx/cpp/dolfinx/fem/Expression.h