shuffle_iterator#

template<class _IndexType = ::cuda::std::size_t, class _Bijection = random_bijection<_IndexType>>
class shuffle_iterator#

shuffle_iterator is an iterator which generates a sequence of integral values representing a random permutation.

shuffle_iterator is an iterator which generates a sequence of values representing a random permutation. This iterator is useful for working with random permutations of a range without explicitly storing them in memory. The shuffle iterator is also useful for sampling from a range by selecting only a subset of the elements in the permutation.

The following code snippet demonstrates how to create a shuffle_iterator which generates a random permutation of the range[0, 4)

#include <cuda/iterator>
...
// create a shuffle_iterator
cuda::shuffle_iterator iterator{cuda::random_bijection{4, cuda::std::minstd_rand(0xDEADBEEF)}};
// iterator[0] returns 1
// iterator[1] returns 3
// iterator[2] returns 2
// iterator[3] returns 0
Template Parameters:

  • _IndexType – The type of the index to shuffle. Defaults to uint64_t

  • _BijectionFunc – The bijection to use. This should be a bijective function that maps [0..n) -> [0..n). It must be deterministic and stateless. Defaults to cuda::random_biijection<_IndexType>

Public Types

using iterator_category = ::cuda::std::random_access_iterator_tag#
using iterator_concept = ::cuda::std::random_access_iterator_tag#
using value_type = _IndexType#
using difference_type = ::cuda::std::make_signed_t<value_type>#

Public Functions

constexpr shuffle_iterator() noexcept = default#
inline constexpr shuffle_iterator(
_Bijection __bijection,
value_type __start = 0,
) noexcept(::cuda::std::is_nothrow_move_constructible_v<_Bijection>)#

Constructs a shuffle_iterator from a given bijection and an optional start position.

Parameters:

  • __bijection – The bijection representing the shuffled integer sequence

  • __start – The position of the iterator in the shuffled integer sequence

template<class _RNG>
inline explicit constexpr shuffle_iterator(
value_type __num_elements,
_RNG &&__gen,
value_type __start = 0,
) noexcept(::cuda::std::is_nothrow_constructible_v<_Bijection, value_type, _RNG>)#

Constructs a shuffle_iterator by constructing the bijection function in place and an optional start position.

Parameters:

  • __num_elements – The size of the bijection sequence

  • __gen – The random number generator to initialize the bijection

  • __start – The optional stating index of the shuffle_iterator in the bijection sequence

inline constexpr value_type operator*(
) const noexcept(noexcept(__bijection_(0)))#

Dereferences the shuffle_iterator by invoking the bijection with the stored index.

inline constexpr value_type operator[](
difference_type __n,
) const noexcept(noexcept(__bijection_(0)))#

Subscripts the shuffle_iterator by invoking the bijection with the stored index advanced by a given number of elements.

Parameters:

__n – The additional number of elements

inline constexpr shuffle_iterator &operator++() noexcept#

Increments the permutation_iterator.

inline constexpr shuffle_iterator operator++(
int,
) noexcept(::cuda::std::is_nothrow_copy_constructible_v<_Bijection>)#

Increments the permutation_iterator.

inline constexpr shuffle_iterator &operator--() noexcept#

Decrements the permutation_iterator.

inline constexpr shuffle_iterator operator--(
int,
) noexcept(::cuda::std::is_nothrow_copy_constructible_v<_Bijection>)#

Decrements the permutation_iterator.

inline constexpr shuffle_iterator &operator+=(
difference_type __n,
) noexcept#

Advances the permutation_iterator by a given number of elements.

Parameters:

__n – The number of elements to advance

inline constexpr shuffle_iterator &operator-=(
difference_type __n,
) noexcept#

Decrements the permutation_iterator by a given number of elements.

Parameters:

__n – The number of elements to decrement

Friends

inline friend constexpr shuffle_iterator operator+(
shuffle_iterator __iter,
difference_type __n,
) noexcept#

Returns a copy of a shuffle_iterator incremented by a given number of elements.

Parameters:

  • __iter – The shuffle_iterator to copy

  • __n – The number of elements to increment

inline friend constexpr shuffle_iterator operator+(
difference_type __n,
shuffle_iterator __iter,
) noexcept#

Returns a copy of a shuffle_iterator incremented by a given number of elements.

Parameters:

  • __n – The number of elements to increment

  • __iter – The shuffle_iterator to copy

inline friend constexpr shuffle_iterator operator-(
shuffle_iterator __iter,
difference_type __n,
) noexcept#

Returns a copy of a shuffle_iterator decremented by a given number of elements.

Parameters:

  • __iter – The shuffle_iterator to copy

  • __n – The number of elements to decrement

inline friend constexpr difference_type operator-(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Calculates the distance between two shuffle_iterator.

inline friend constexpr bool operator==(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Compares two shuffle_iterator for equality by comparing their index.

inline friend constexpr bool operator<(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Compares two shuffle_iterator for less than by comparing their index.

inline friend constexpr bool operator>(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Compares two shuffle_iterator for greater than by comparing their index.

inline friend constexpr bool operator<=(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Compares two shuffle_iterator for less equal by comparing their index.

inline friend constexpr bool operator>=(
const shuffle_iterator &__x,
const shuffle_iterator &__y,
) noexcept#

Compares two shuffle_iterator for greater equal by comparing their index.

template<class _Bijection, class _IndexType>
inline constexpr auto make_shuffle_iterator(
_Bijection __fun,
_IndexType __start = 0,
)#

make_shuffle_iterator creates a shuffle_iterator from an integer and a bijection function

Parameters:

  • __fun – The bijection function used for shuffling

  • __start – The starting position of the shuffle_iterator