cadabra::NEvaluator Class Reference

Description

Functionality to numerically evaluate a scalar expression, give the values of its building blocks.

The input is a map which relates subtrees in the expression to numerical values. The evaluate function will then do a post-order iteration over the tree, collecting and combining the values thus obtained.

Currently needs the leaf nodes to have an entry in the subtree_values map; may be extended later to cover values of non-elementary subtrees.

If there are 'n' variables, then at any stage the tree will be an n-tensor, with the dimension of each index set by the length of the value array for the corresponding variable.

#include <NEvaluator.hh>

Classes
class	VariableValues
	The expression will get evaluated for a range of values for each unknown sub-expression (variable). More...

Public Types
typedef std::function< std::complex< double >(const Ex &)>	lookup_function_t
	Set an external function which will be used by evaluate to lookup values of objects as a last resort, if they do not resolve using the variable_values list above.

Public Member Functions
	NEvaluator ()
	NEvaluator (Ex::iterator)
void	set_function (Ex::iterator)
	Set function to evaluate. Can also be passed in the constructor.
void	set_variable (const Ex &, const NTensor &val)
	Set the range of values which we want to insert into the indicated variable.
void	set_lookup_function (lookup_function_t)
NTensor	evaluate ()
	Evaluate the expression, using the variable values set in set_variable.
void	find_variable_locations ()
	PRIVATE:

Public Attributes
std::map< Ex::iterator, NTensor, Ex::iterator_base_less >	subtree_values
	If we know the value of a subtree explicitly as a number, it is stored in this map.
std::map< Ex::iterator, Ex::iterator, Ex::iterator_base_less >	subtree_equalities
	If we know the value of a subtree is equal to another subtree (either in the same expression or another one), it is stored in the map below.
std::vector< VariableValues >	variable_values
std::map< Ex, size_t, tree_exact_less_no_wildcards_obj >	variable_values_locs

Private Attributes
Ex	ex
lookup_function_t	lookup_function
std::vector< size_t >	fullshape

Member Typedef Documentation

lookup_function_t

typedef std::function<std::complex<double>(const Ex&)> cadabra::NEvaluator::lookup_function_t

Set an external function which will be used by evaluate to lookup values of objects as a last resort, if they do not resolve using the variable_values list above.

Constructor & Destructor Documentation

NEvaluator() [1/2]

NEvaluator::NEvaluator

(

)

NEvaluator() [2/2]

NEvaluator::NEvaluator

(

Ex::iterator

ex_it

)

Member Function Documentation

evaluate()

NTensor NEvaluator::evaluate

(

)

Evaluate the expression, using the variable values set in set_variable.

This will only work if the expression evaluates to a complex double.

find_variable_locations()

void NEvaluator::find_variable_locations

(

)

PRIVATE:

set_function()

void NEvaluator::set_function

(

Ex::iterator

ex_it

)

Set function to evaluate. Can also be passed in the constructor.

set_lookup_function()

void NEvaluator::set_lookup_function

(

lookup_function_t

f

)

set_variable()

void NEvaluator::set_variable	(	const Ex &	var,
		const NTensor &	val
	)

Set the range of values which we want to insert into the indicated variable.

Fills the map above.

Member Data Documentation

ex

Ex cadabra::NEvaluator::ex

private

fullshape

std::vector<size_t> cadabra::NEvaluator::fullshape

private

lookup_function

lookup_function_t cadabra::NEvaluator::lookup_function

private

subtree_equalities

std::map<Ex::iterator, Ex::iterator, Ex::iterator_base_less> cadabra::NEvaluator::subtree_equalities

If we know the value of a subtree is equal to another subtree (either in the same expression or another one), it is stored in the map below.

This then still needs a lookup in the subtree_values map. FIXME: not used right now. The idea was that if we find two subtrees which are equal symbolically, we only have to evaluate one, and can then read off the value of the other one by referring to the first.

subtree_values

std::map<Ex::iterator, NTensor, Ex::iterator_base_less> cadabra::NEvaluator::subtree_values

If we know the value of a subtree explicitly as a number, it is stored in this map.

These are computed nodes. Note that keys are compared as pointers, so two identical expressions at two different locations in the tree will have two entries in this map.

variable_values

std::vector<VariableValues> cadabra::NEvaluator::variable_values

variable_values_locs

std::map<Ex, size_t, tree_exact_less_no_wildcards_obj> cadabra::NEvaluator::variable_values_locs

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

• core/NEvaluator.hh
• core/NEvaluator.cc