xbroadcast

Defined in xtensor/xbroadcast.hpp

template <class CT, class X>
class xt::xbroadcast

Broadcasted xexpression to a specified shape.

The xbroadcast class implements the broadcasting of an xexpression to a specified shape. xbroadcast is not meant to be used directly, but only with the broadcast helper functions.

See
broadcast
Template Parameters
  • CT: the closure type of the xexpression to broadcast
  • X: the type of the specified shape.

Inherits from xt::xsharable_expression< xbroadcast< CT, X > >, xt::xconst_iterable< xbroadcast< CT, X > >, xt::xconst_accessible< xbroadcast< CT, X > >, extension::xbroadcast_base_t< CT, X >

Constructor

template <class CTA, class S>
xbroadcast(CTA &&e, const S &s)

Constructs an xbroadcast expression broadcasting the specified xexpression to the given shape.

Parameters
  • e: the expression to broadcast
  • s: the shape to apply

template <class CTA>
xbroadcast(CTA &&e, shape_type &&s)

Constructs an xbroadcast expression broadcasting the specified xexpression to the given shape.

Parameters
  • e: the expression to broadcast
  • s: the shape to apply

Size and shape

auto shape() const

Returns the shape of the expression.

layout_type layout() const

Returns the layout_type of the expression.

Data

auto expression() const

Returns a constant reference to the underlying expression of the broadcast expression.

template <class… Args>
auto operator()(Args... args) const

Returns a constant reference to the element at the specified position in the expression.

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 expression.

template <class… Args>
auto unchecked(Args... args) const

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 prefered 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.uncheked(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>
auto element(It, It last) const

Returns a constant reference to the element at the specified position in the expression.

Parameters
  • first: iterator starting the sequence of indices
  • last: 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 function.

Broadcasting

template <class S>
bool broadcast_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 shape
  • reuse_cache: parameter for internal optimization

template <class S>
bool has_linear_assign(const S &strides) const

Checks whether the xbroadcast can be linearly assigned to an expression with the specified strides.

Return
a boolean indicating whether a linear assign is possible

Public Functions

auto size() const

Returns the size of the expression.

auto shape(size_type index) const

Returns the i-th dimension of the expression.

template <class E, class S>
auto xt::broadcast(E &&e, const S &s)

Returns an xexpression broadcasting the given expression to a specified shape.

The returned expression either hold a const reference to e or a copy depending on whether e is an lvalue or an rvalue.

Template Parameters
  • e: the xexpression to broadcast
  • s: the specified shape to broadcast.