xfunction¶
Defined in xtensor/xfunction.hpp
-
template<class
F
, class ...CT
>
classxt
::
xfunction
: private xt::xconst_iterable<xfunction<F, CT...>>, public xt::xsharable_expression<xfunction<F, CT...>>, private xt::xconst_accessible<xfunction<F, CT...>>, public extension::xfunction_base_t<F, CT...>¶ Multidimensional function operating on xtensor expressions.
The xfunction class implements a multidimensional function operating on xtensor expressions.
- Template Parameters
F
: the function typeCT
: the closure types for arguments of the function
Constructor
-
template<class
Func
, class ...CTA
, classU
= std::enable_if_t<!std::is_base_of<std::decay_t<Func>, self_type>::value>>xfunction
(Func &&f, CTA&&... e) noexcept¶ Constructs an xfunction applying the specified function to the given arguments.
- Parameters
f
: the function to applye
: the xexpression arguments
Size and shape
-
size_type
dimension
() const noexcept¶ Returns the number of dimensions of the function.
-
const inner_shape_type &
shape
() const¶ Returns the shape of the xfunction.
-
layout_type
layout
() const noexcept¶ Returns the layout_type of the xfunction.
Broadcasting
-
template<class
S
>
boolbroadcast_shape
(S &shape, bool reuse_cache = false) const¶ Broadcast the shape of the function to the specified parameter.
- Return
a boolean indicating whether the broadcasting is trivial
- Parameters
shape
: the result shapereuse_cache
: boolean for reusing a previously computed shape
Data
-
const_reference
flat
(size_type i) const¶ Returns a constant reference to the element at the specified position of the underlying contiguous storage of the function.
- Parameters
index
: index to underlying flat storage.
-
template<class ...
Args
>
autooperator()
(Args... args) const -> const_reference¶ Returns a constant reference to the element at the specified position in the function.
- Parameters
args
: a list of indices specifying the position in the function. Indices must be unsigned integers, the number of indices should be equal or greater than the number of dimensions of the function.
-
template<class ...
Args
>
autounchecked
(Args... args) const -> const_reference¶ Returns a constant reference to the element at the specified position in the expression.
- Warning
This method is meant for performance, for expressions with a dynamic number of dimensions (i.e. not known at compile time). Since it may have undefined behavior (see parameters), operator() should be preferred whenever it is possible.
- Warning
This method is NOT compatible with broadcasting, meaning the following code has undefined behavior:
xt::xarray<double> a = {{0, 1}, {2, 3}}; xt::xarray<double> b = {0, 1}; auto fd = a + b; double res = fd.unchecked(0, 1);
- Parameters
args
: a list of indices specifying the position in the expression. Indices must be unsigned integers, the number of indices must be equal to the number of dimensions of the expression, else the behavior is undefined.
-
template<class
It
>
autoelement
(It first, It last) const -> const_reference¶ Returns a constant reference to the element at the specified position in the function.
- Parameters
first
: iterator starting the sequence of indiceslast
: iterator ending the sequence of indices The number of indices in the sequence should be equal to or greater than the number of dimensions of the container.
Public Functions
-
size_type
size
() const noexcept¶ Returns the size of the expression.
-
size_type
shape
(size_type index) const¶ Returns the i-th dimension of the expression.
-
template<class ...
Args
>
autoat
(Args... args) const -> const_reference¶ Returns a constant reference to the element at the specified position in the expression, after dimension and bounds checking.
- Parameters
args
: a list of indices specifying the position in the expression. Indices must be unsigned integers, the number of indices should be equal to the number of dimensions of the expression.
- Exceptions
std::out_of_range
: if the number of argument is greater than the number of dimensions or if indices are out of bounds.
-
template<class ...
Args
>
autoperiodic
(Args... args) const -> const_reference¶ Returns a constant reference to the element at the specified position in the expression, after applying periodicity to the indices (negative and ‘overflowing’ indices are changed).
- Parameters
args
: a list of indices specifying the position in the expression. Indices must be integers, the number of indices should be equal to the number of dimensions of the expression.
-
template<class ...
Args
>
boolin_bounds
(Args... args) const¶ Returns
true
only if the the specified position is a valid entry in the expression.- Return
bool
- Parameters
args
: a list of indices specifying the position in the expression.
-
const_reference
front
() const¶ Returns a constant reference to first the element of the expression.
-
const_reference
back
() const¶ Returns a constant reference to last the element of the expression.
Defined in xtensor/xmath.hpp
-
template<class
F
, class ...E
>
autoxt
::
make_lambda_xfunction
(F &&lambda, E&&... args)¶ Create a xfunction from a lambda.
This function can be used to easily create performant xfunctions from lambdas:
template <class E1> inline auto square(E1&& e1) noexcept { auto fnct = [](auto x) -> decltype(x * x) { return x * x; }; return make_lambda_xfunction(std::move(fnct), std::forward<E1>(e1)); }
Lambda function allow the reusal of a single arguments in multiple places (otherwise only correctly possible when using xshared_expressions).
auto
lambda functions are automatically vectorized withxsimd
if possible (note that the trailing-> decltype(...)
is mandatory for the feature detection to work).- Return
lazy xfunction
- Parameters
lambda
: the lambda to be vectorizedargs
: forwarded arguments