TensorFunctionParser< rank, dim, Number > Class Template Reference

#include <deal.II/base/tensor_function_parser.h>

Inheritance diagram for TensorFunctionParser< rank, dim, Number >:

Public Types
using	ConstMap = std::map< std::string, double >
Public Types inherited from TensorFunction< rank, dim, double >
using	value_type = Tensor< rank, dim, double >
using	gradient_type = Tensor< rank+1, dim, double >
using	time_type = typename FunctionTime< typename numbers::NumberTraits< double >::real_type >::time_type
Public Types inherited from FunctionTime< numbers::NumberTraits< double >::real_type >
using	time_type = numbers::NumberTraits< double >::real_type

Public Member Functions
	TensorFunctionParser (const double initial_time=0.0)
	TensorFunctionParser (const std::string &expression, const std::string &constants="", const std::string &variable_names=default_variable_names()+",t")
	TensorFunctionParser (const TensorFunctionParser &)=delete
	TensorFunctionParser (TensorFunctionParser &&)=delete
virtual	~TensorFunctionParser () override
TensorFunctionParser &	operator= (const TensorFunctionParser &)=delete
TensorFunctionParser &	operator= (TensorFunctionParser &&)=delete
void	initialize (const std::string &vars, const std::vector< std::string > &expressions, const ConstMap &constants, const bool time_dependent=false)
void	initialize (const std::string &vars, const std::string &expression, const ConstMap &constants, const bool time_dependent=false)
virtual Tensor< rank, dim, Number >	value (const Point< dim > &p) const override
virtual void	value_list (const std::vector< Point< dim >> &p, std::vector< Tensor< rank, dim, Number >> &values) const override
const std::vector< std::string > &	get_expressions () const
Public Member Functions inherited from TensorFunction< rank, dim, double >
	TensorFunction (const time_type initial_time=time_type(0.0))
virtual	~TensorFunction () override=default
virtual void	value_list (const std::vector< Point< dim >> &points, std::vector< value_type > &values) const
virtual gradient_type	gradient (const Point< dim > &p) const
virtual void	gradient_list (const std::vector< Point< dim >> &points, std::vector< gradient_type > &gradients) const
Public Member Functions inherited from FunctionTime< numbers::NumberTraits< double >::real_type >
	FunctionTime (const numbers::NumberTraits< double >::real_type initial_time=numbers::NumberTraits< double >::real_type(0.0))
virtual	~FunctionTime ()=default
numbers::NumberTraits< double >::real_type	get_time () const
virtual void	set_time (const numbers::NumberTraits< double >::real_type new_time)
virtual void	advance_time (const numbers::NumberTraits< double >::real_type delta_t)
Public Member Functions inherited from Subscriptor
	Subscriptor ()
	Subscriptor (const Subscriptor &)
	Subscriptor (Subscriptor &&) noexcept
virtual	~Subscriptor ()
Subscriptor &	operator= (const Subscriptor &)
Subscriptor &	operator= (Subscriptor &&) noexcept
void	subscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
void	unsubscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
unsigned int	n_subscriptions () const
template<typename StreamType >
void	list_subscribers (StreamType &stream) const
void	list_subscribers () const
template<class Archive >
void	serialize (Archive &ar, const unsigned int version)

Static Public Member Functions
static std::string	default_variable_names ()
static ::ExceptionBase &	ExcParseError (int arg1, std::string arg2)
static ::ExceptionBase &	ExcInvalidExpressionSize (int arg1, int arg2)
Static Public Member Functions inherited from Subscriptor
static ::ExceptionBase &	ExcInUse (int arg1, std::string arg2, std::string arg3)
static ::ExceptionBase &	ExcNoSubscriber (std::string arg1, std::string arg2)

Private Member Functions
void	init_muparser () const

Private Attributes
Threads::ThreadLocalStorage< std::vector< double > >	vars
Threads::ThreadLocalStorage< std::vector< std::unique_ptr< mu::Parser > > >	tfp
std::map< std::string, double >	constants
std::vector< std::string >	var_names
std::vector< std::string >	expressions
bool	initialized
unsigned int	n_vars
unsigned int	n_components

Detailed Description

template<int rank, int dim, typename Number = double>
class TensorFunctionParser< rank, dim, Number >

This class implements a tensor function object that gets its value by parsing a string describing this function. It is a wrapper class for the muparser library (see http://muparser.beltoforion.de/). This class is essentially an extension of the FunctionParser class to read in a TensorFunction. The class reads in an expression of length dim^rank (separated by a semicolon) where the components of the tensor function are filled according to the C++ convention (fastest index is the most right one).

Note

In contrast to the FunctionParser class the TensorFunctionParser class does not support automatic differentiation.

A minimal example for the usage of the class would be:

// set up time dependent tensor function:
const std::string variables = "x,y,t";
const std::string expression =
      "exp(-t)*cos(x+y);-sin(pi*x*y-t);sin(pi*x*y-t);exp(t)*cos(x+y)";
std::map<std::string,double> constants;
constants["pi"] = numbers::PI;
 
// TensorFunctionParser with 2+1 variables (space + time) in 2D of rank 2.
// It is necessary to tell the parser that there is an additional variable
// to be taken into account (t).
TensorFunctionParser<2,2> tfp;
tfp.initialize(variables,
              expression,
              constants,
              true); // flag for time dependence
 
// Point at which we want to evaluate the function
Point<2> point(0.0, 1.0);
 
// evaluate the expression at 'point':
double result = tfp.value(point);
 
deallog << "Function '" << expression << "'"
        << " @ " << point
        << " is: "
        << std::endl
        << result[0][0] << " " << result[0][1] << std::endl
        << result[1][0] << " " << result[1][1]
        << std::endl;

See also the documentation of the FunctionParser class.

This class overloads the virtual method value() and value_list() of the TensorFunction base class with the byte compiled versions of the expressions given to the initialize() methods. Note that the class will not work unless you first call the initialize() method that accepts the text description of the function as an argument (among other things).

The syntax to describe a function follows usual programming practice, and is explained in detail at the homepage of the underlying muparser library at http://muparser.beltoforion.de/ .

Vector-valued functions can either be declared using strings where the function components are separated by semicolons, or using a vector of strings each defining one vector component.

Author

Konrad Simon, 2019

Definition at line 112 of file tensor_function_parser.h.

Member Typedef Documentation

ConstMap

template<int rank, int dim, typename Number = double>

using TensorFunctionParser< rank, dim, Number >::ConstMap = std::map<std::string, double>

Type for the constant map. Used by the initialize() method.

Definition at line 170 of file tensor_function_parser.h.

Constructor & Destructor Documentation

TensorFunctionParser() [1/4]

template<int rank, int dim, typename Number >

TensorFunctionParser< rank, dim, Number >::TensorFunctionParser

(

const double

initial_time = 0.0

)

Standard constructor. Only set initial time. This object needs to be initialized with the initialize() method before you can use it. If an attempt to use this function is made before the initialize() method has been called, then an exception is thrown.

Definition at line 45 of file tensor_function_parser.cc.

TensorFunctionParser() [2/4]

template<int rank, int dim, typename Number >

TensorFunctionParser< rank, dim, Number >::TensorFunctionParser	(	const std::string &	expression,
		const std::string &	constants = "",
		const std::string &	variable_names = default_variable_names() + ",t"
	)

Constructor for parsed functions. This object needs to be initialized with the initialize() method before you can use it. If an attempt to use this function is made before the initialize() method has been called, then an exception is thrown. Takes a semicolon separated list of expressions (one for each component of the tensor function), an optional comma-separated list of constants.

Definition at line 55 of file tensor_function_parser.cc.

TensorFunctionParser() [3/4]

template<int rank, int dim, typename Number = double>

TensorFunctionParser< rank, dim, Number >::TensorFunctionParser ( const TensorFunctionParser< rank, dim, Number > &  )

delete

Copy constructor. Objects of this type can not be copied, and consequently this constructor is deleted.

TensorFunctionParser() [4/4]

template<int rank, int dim, typename Number = double>

TensorFunctionParser< rank, dim, Number >::TensorFunctionParser ( TensorFunctionParser< rank, dim, Number > &&  )

delete

Move constructor. Objects of this type can not be moved, and consequently this constructor is deleted.

~TensorFunctionParser()

template<int rank, int dim, typename Number >

TensorFunctionParser< rank, dim, Number >::~TensorFunctionParser ( )

overridevirtualdefault

Destructor.

Member Function Documentation

operator=() [1/2]

template<int rank, int dim, typename Number = double>

TensorFunctionParser& TensorFunctionParser< rank, dim, Number >::operator= ( const TensorFunctionParser< rank, dim, Number > &  )

delete

Copy operator. Objects of this type can not be copied, and consequently this operator is deleted.

operator=() [2/2]

template<int rank, int dim, typename Number = double>

TensorFunctionParser& TensorFunctionParser< rank, dim, Number >::operator= ( TensorFunctionParser< rank, dim, Number > &&  )

delete

Move operator. Objects of this type can not be moved, and consequently this operator is deleted.

initialize() [1/2]

template<int rank, int dim, typename Number >

void TensorFunctionParser< rank, dim, Number >::initialize	(	const std::string &	vars,
		const std::vector< std::string > &	expressions,
		const ConstMap &	constants,
		const bool	time_dependent = false
	)

Initialize the tensor function. This method accepts the following parameters:

Parameters

[in]	vars	A string with the variables that will be used by the expressions to be evaluated. Note that the variables can have any name (of course different from the function names defined above!), but the order IS important. The first variable will correspond to the first component of the point in which the function is evaluated, the second variable to the second component and so forth. If this function is also time dependent, then it is necessary to specify it by setting the time_dependent parameter to true. An exception is thrown if the number of variables specified here is different from dim (if this function is not time-dependent) or from dim+1 (if it is time-dependent).
[in]	expressions	A vector of strings containing the expressions that will be byte compiled by the internal parser (TensorFunctionParser). Note that the size of this vector must match exactly the number of components of the TensorFunctionParser, as declared in the constructor. If this is not the case, an exception is thrown.
[in]	constants	A map of constants used to pass any necessary constant that we want to specify in our expressions (in the example above the number pi). An expression is valid if and only if it contains only defined variables and defined constants (other than the functions specified above). If a constant is given whose name is not valid (eg: constants["sin"] = 1.5;) an exception is thrown.
[in]	time_dependent	If this is a time dependent function, then the last variable declared in vars is assumed to be the time variable, and this->get_time() is used to initialize it when evaluating the function. Naturally the number of variables parsed by the initialize() method in this case is dim+1. The value of this parameter defaults to false, i.e. do not consider time.

Definition at line 91 of file tensor_function_parser.cc.

initialize() [2/2]

template<int rank, int dim, typename Number >

void TensorFunctionParser< rank, dim, Number >::initialize	(	const std::string &	vars,
		const std::string &	expression,
		const ConstMap &	constants,
		const bool	time_dependent = false
	)

Initialize the function. Same as above, but accepts a string rather than a vector of strings. If this is a vector valued function, its components are expected to be separated by a semicolon. An exception is thrown if this method is called and the number of components successfully parsed does not match the number of components of the base function.

Definition at line 272 of file tensor_function_parser.cc.

default_variable_names()

template<int rank, int dim, typename Number >

std::string TensorFunctionParser< rank, dim, Number >::default_variable_names

static

A function that returns default names for variables, to be used in the first argument of the initialize() functions: it returns "x" in 1d, "x,y" in 2d, and "x,y,z" in 3d.

Definition at line 341 of file tensor_function_parser.h.

value()

template<int rank, int dim, typename Number >

Tensor< rank, dim, Number > TensorFunctionParser< rank, dim, Number >::value ( const Point< dim > &  p ) const

overridevirtual

Return the value of the tensor function at the given point.

Reimplemented from TensorFunction< rank, dim, double >.

Definition at line 288 of file tensor_function_parser.cc.

value_list()

template<int rank, int dim, typename Number >

void TensorFunctionParser< rank, dim, Number >::value_list ( const std::vector< Point< dim >> &  p, std::vector< Tensor< rank, dim, Number >> &  values  ) const

overridevirtual

Return the value of the tensor function at the given point.

Definition at line 333 of file tensor_function_parser.cc.

get_expressions()

template<int rank, int dim, typename Number >

const std::vector< std::string > & TensorFunctionParser< rank, dim, Number >::get_expressions

Return an array of function expressions (one per component), used to initialize this function.

Definition at line 37 of file tensor_function_parser.cc.

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

• include/deal.II/base/tensor_function_parser.h
• source/base/tensor_function_parser.cc