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Add specialization for is_bitwise_comparable<cuco::pair>> #335

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Add specialization for is_bitwise_comparable<cuco::pair>> #335

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4376e78
Add specialization for is_bitwise_comparable<cuco::pair>>
sleeepyjack Jul 18, 2023
bf39284
Check for padding
sleeepyjack Jul 18, 2023
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9 changes: 9 additions & 0 deletions include/cuco/detail/traits.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,15 @@

namespace cuco::detail {

template <typename T, typename = void>
struct is_bitwise_comparable_impl : std::false_type {
};

template <typename T>
struct is_bitwise_comparable_impl<T, std::enable_if_t<std::has_unique_object_representations_v<T>>>
: std::true_type {
};

template <typename T, typename = void>
struct is_std_pair_like : cuda::std::false_type {
};
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10 changes: 10 additions & 0 deletions include/cuco/pair.cuh
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Expand Up @@ -18,6 +18,7 @@

#include <cuco/detail/traits.hpp>
#include <cuco/detail/utils.cuh>
#include <cuco/utility/traits.hpp>

#include <thrust/device_reference.h>
#include <thrust/tuple.h>
Expand Down Expand Up @@ -141,6 +142,15 @@ template <class T1, class T2, class U1, class U2>
__host__ __device__ constexpr bool operator==(cuco::pair<T1, T2> const& lhs,
cuco::pair<U1, U2> const& rhs) noexcept;

/**
* @brief A pair of bitwise comparable types is also bitwise comparable
*/
template <typename First, typename Second>
struct is_bitwise_comparable<pair<First, Second>>
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This is dangerous. If someone used a pair<char, int> as their key type, then it would be considered bitwise comparable, even though it would have padding bits.

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Right. would adding && sizeof(pair<First, Second>) == sizeof(First)+sizeof(Second) help?

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Remind me where we need to perform a bitwise equality on a pair?

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Here: https://github.com/NVIDIA/cuCollections/blob/a2833dbfb1b7d4915d530bd6adb45092a87a3b07/include/cuco/detail/open_addressing_ref_impl.cuh#L659C5-L659C76

For a static_map, the value_type of the underlying open_addressing_impl is cuco::pair<Key, Value>.

: std::integral_constant<bool,
is_bitwise_comparable_v<First> && is_bitwise_comparable_v<Second>> {
};

} // namespace cuco

#include <cuco/detail/pair.inl>
12 changes: 3 additions & 9 deletions include/cuco/utility/traits.hpp
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Expand Up @@ -16,8 +16,7 @@

#pragma once

#include <thrust/device_reference.h>
#include <thrust/tuple.h>
#include <cuco/detail/traits.hpp>

#include <type_traits>

Expand All @@ -36,15 +35,10 @@ namespace cuco {
* if a `NaN` bit pattern were used as the empty sentinel value, it may not compare bitwise equal to
* other `NaN` bit patterns.
*
* @note By default, only types with unique object representations are allowed
*/
template <typename T, typename = void>
struct is_bitwise_comparable : std::false_type {
};

/// By default, only types with unique object representations are allowed
template <typename T>
struct is_bitwise_comparable<T, std::enable_if_t<std::has_unique_object_representations_v<T>>>
: std::true_type {
struct is_bitwise_comparable : detail::is_bitwise_comparable_impl<T> {
};

template <typename T>
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