Utility Span

group Exception

Typedefs

template<typename T, std::size_t Extent = cuda::std::dynamic_extent>
using device_span = cuda::std::span<T, Extent>

Device span is an alias of cuda::std::span.

Variables

constexpr std::size_t dynamic_extent = cuda::std::dynamic_extent

A constant used to differentiate std::span of static and dynamic extent.

template<typename T>
struct is_host_span_supported_container : public std::false_type

template<typename T, typename Alloc>
struct is_host_span_supported_container<std::vector<T, Alloc>> : public std::true_type

template<typename T, typename Alloc>
struct is_host_span_supported_container<thrust::host_vector<T, Alloc>> : public std::true_type

template<typename T, typename Alloc>
struct is_host_span_supported_container<std::basic_string<T, std::char_traits<T>, Alloc>> : public std::true_type

template<typename T, std::size_t Extent = cudf::dynamic_extent>
struct host_span

#include <cudf/utilities/span.hpp>

Host span, a non-owning view over a contiguous sequence of host-accessible elements.

Backed by cuda::std::span, with additional support for constructing from cudf-supported host containers and for tracking whether the underlying memory is device accessible (e.g. pinned memory), which enables copy engine optimizations.

Public Types

using element_type = typename span_type::element_type

Element type.

using value_type = typename span_type::value_type

Stored value type.

using size_type = typename span_type::size_type

Size type.

using difference_type = typename span_type::difference_type

std::ptrdiff_t

using pointer = typename span_type::pointer

Pointer returned by data()

using const_pointer = typename span_type::const_pointer

Pointer returned by data() const.

using reference = typename span_type::reference

Reference returned by operator[].

using const_reference = typename span_type::const_reference

Const reference to an element.

using iterator = pointer

The type of the iterator returned by begin()

Public Functions

inline constexpr host_span(T *data, std::size_t size)

Constructs a span from a pointer and a size.

Note

This needs to be host-device, as it’s used by a host-device function in base_2dspan

Parameters:

• data – Pointer to the first element in the span

• size – The number of elements in the span

inline constexpr host_span(

T *data,

std::size_t size,

bool is_device_accessible

)

Constructor from pointer, size and device-accessibility flag.

Note

This needs to be host-device, as it’s used by a host-device function in base_2dspan

Parameters:

• data – Pointer to the first element in the span

• size – The number of elements in the span

• is_device_accessible – Whether the data is device accessible (e.g. pinned memory)

template<typename C>
inline constexpr host_span(C &in)

Constructor from container

Parameters:

in – The container to construct the span from

template<typename C>
inline constexpr host_span(C const &in)

Constructor from const container

Parameters:

in – The container to construct the span from

template<typename OtherT, std::size_t OtherExtent>
inline constexpr host_span(

host_span<OtherT, OtherExtent> const &other

) noexcept

Parameters:

other – The span to copy

inline constexpr reference operator[](size_type idx) const

Returns a reference to the idx-th element of the sequence.

The behavior is undefined if idx is out of range (i.e., if it is greater than or equal to size()).

Parameters:

idx – the index of the element to access

Returns:

A reference to the idx-th element of the sequence, i.e., data()[idx]

inline constexpr reference front() const

Returns a reference to the first element in the span.

Calling front on an empty span results in undefined behavior.

Returns:

Reference to the first element in the span

inline constexpr reference back() const

Returns a reference to the last element in the span.

Calling back on an empty span results in undefined behavior.

Returns:

Reference to the last element in the span

inline constexpr iterator begin() const noexcept

Returns an iterator to the first element of the span.

If the span is empty, the returned iterator will be equal to end().

Returns:

An iterator to the first element of the span

inline constexpr iterator end() const noexcept

Returns an iterator to the element following the last element of the span.

This element acts as a placeholder; attempting to access it results in undefined behavior.

Returns:

An iterator to the element following the last element of the span

inline constexpr pointer data() const noexcept

Returns a pointer to the beginning of the sequence.

Returns:

A pointer to the first element of the span

inline constexpr size_type size() const noexcept

Returns the number of elements in the span.

Returns:

The number of elements in the span

inline constexpr size_type size_bytes() const noexcept

Returns the size of the sequence in bytes.

Returns:

The size of the sequence in bytes

inline constexpr bool empty() const noexcept

Checks if the span is empty.

Returns:

True if the span is empty, false otherwise

inline constexpr host_span first(size_type count) const noexcept

Obtains a subspan consisting of the first count elements of the sequence.

Parameters:

count – Number of elements from the beginning of this span to put in the subspan.

Returns:

A subspan of the first count elements of the sequence

inline constexpr host_span last(size_type count) const noexcept

Obtains a subspan consisting of the last count elements of the sequence.

Parameters:

count – Number of elements from the end of this span to put in the subspan

Returns:

A subspan of the last count elements of the sequence

inline bool is_device_accessible() const

Returns whether the data is device accessible (e.g. pinned memory)

Returns:

true if the data is device accessible

inline constexpr host_span subspan(

size_type offset,

size_type count

) const noexcept

Obtains a span that is a view over the count elements of this span starting at offset.

Parameters:

• offset – The offset of the first element in the subspan

• count – The number of elements in the subspan

Returns:

A subspan of the sequence, of requested count and offset

inline constexpr operator std::span<T>() const noexcept

Returns a standard span instance.

Returns:

Standard span instance

Public Static Attributes

static constexpr std::size_t extent = span_type::extent

The extent of the span.