Expression< T, U > Class Template Reference

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 > cells, std::span< scalar_type > values, std::array< std::size_t, 2 > vshape) const
	Evaluate Expression on cells.
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 = dolfinx::scalar_value_type_t<T>>
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 = dolfinx::scalar_value_type_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_type_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 *)>  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 reference cell, shape=(number of points, tdim) and storage is row-major.
[in]	Xshape	Shape of X.
[in]	fn	function for tabulating 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 = dolfinx::scalar_value_type_t<T>>

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 = dolfinx::scalar_value_type_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 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 = dolfinx::scalar_value_type_t<T>>

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 = dolfinx::scalar_value_type_t<T>>

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 = dolfinx::scalar_value_type_t<T>>

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

inline

Evaluate Expression on cells.

Parameters

[in]	mesh	Cells on which to evaluate the Expression.
[in]	cells	Cells on which to evaluate the Expression.
[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).
[in]	vshape	The shape of values (row-major storage).

get_tabulate_expression()

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

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 = dolfinx::scalar_value_type_t<T>>

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 = dolfinx::scalar_value_type_t<T>>

int value_size ( ) const

inline

Get value size.

Returns

The value size.

X()

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

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

inline

Evaluation points on the reference cell.

Returns

Evaluation points.

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

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