Expression< T > Class Template Reference

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. More...

#include <Expression.h>

Public Types
using	scalar_type = T
	Scalar type (T)

Public Member Functions
	Expression (const std::vector< std::shared_ptr< const Function< T >>> &coefficients, const std::vector< std::shared_ptr< const Constant< T >>> &constants, const xt::xtensor< double, 2 > &X, const std::function< void(T *, const T *, const T *, const double *, const int *, const uint8_t *)> fn, const std::vector< int > &value_shape, const std::shared_ptr< const mesh::Mesh > &mesh=nullptr, const std::shared_ptr< const FunctionSpace > argument_function_space=nullptr)
	Create an Expression. More...
	Expression (Expression &&form)=default
	Move constructor.
virtual	~Expression ()=default
	Destructor.
std::shared_ptr< const fem::FunctionSpace >	argument_function_space () const
	Get argument function space. More...
const std::vector< std::shared_ptr< const fem::Function< T > > > &	coefficients () const
	Get coefficients. More...
const std::vector< std::shared_ptr< const fem::Constant< T > > > &	constants () const
	Get constants. More...
std::vector< int >	coefficient_offsets () const
	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.
template<typename U >
void	eval (const xtl::span< const std::int32_t > &cells, U &values) const
	Evaluate the expression on cells. More...
const std::function< void(T *, const T *, const T *, const double *, const int *, const uint8_t *)> &	get_tabulate_expression () const
	Get function for tabulate_expression. More...
std::shared_ptr< const mesh::Mesh >	mesh () const
	Get mesh. More...
int	value_size () const
	Get value size. More...
const std::vector< int > &	value_shape () const
	Get value shape. More...
const xt::xtensor< double, 2 > &	X () const
	Get evaluation points on reference cell. More...

Detailed Description

template<typename T>
class dolfinx::fem::Expression< T >

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.

This 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.

Constructor & Destructor Documentation

Expression()

Expression ( const std::vector< std::shared_ptr< const Function< T >>> &  coefficients, const std::vector< std::shared_ptr< const Constant< T >>> &  constants, const xt::xtensor< double, 2 > &  X, const std::function< void(T *, const T *, const T *, const double *, const int *, const uint8_t *)>  fn, const std::vector< int > &  value_shape, const std::shared_ptr< const mesh::Mesh > &  mesh = nullptr, const std::shared_ptr< const FunctionSpace >  argument_function_space = nullptr  )

inline

Create an Expression.

Users should prefer the create_expression factory functions

Parameters

[in]	coefficients	Coefficients in the Expression
[in]	constants	Constants in the Expression
[in]	mesh
[in]	X	points on reference cell, number of points rows and tdim cols
[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()

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

inline

Get argument function space.

Returns

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

coefficients()

const std::vector<std::shared_ptr<const fem::Function<T> > >& coefficients ( ) const

inline

Get coefficients.

Returns

Vector of attached coefficients

constants()

const std::vector<std::shared_ptr<const fem::Constant<T> > >& 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()

void eval ( const xtl::span< const std::int32_t > &  cells, U &  values  ) const

inline

Evaluate the expression on cells.

Parameters

[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).

get_tabulate_expression()

const std::function<void(T*, const T*, const T*, const double*, const int*, const uint8_t*)>& get_tabulate_expression ( ) const

inline

Get function for tabulate_expression.

Returns

fn Function to tabulate expression.

mesh()

std::shared_ptr<const mesh::Mesh> mesh ( ) const

inline

Get mesh.

Returns

The mesh

value_shape()

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

inline

Get value shape.

Returns

value shape

value_size()

int value_size ( ) const

inline

Get value size.

Returns

value_size

X()

const xt::xtensor<double, 2>& X ( ) const

inline

Get evaluation points on 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