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Merged
bernhardmgruber merged 3 commits into from
Sep 22, 2025
+60 −46
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Improve thrust::cuda_cub::replace functor handling #5949

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5aaae14
Cleanup and improve thrust::cuda_cub::replace
bernhardmgruber Sep 19, 2025
bf50f3c
attro
bernhardmgruber Sep 19, 2025
4420081
Use `_CCCL_DEVICE_API` instead of `THRUST_DEVICE_FUNCTION`
miscco Sep 22, 2025
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13 changes: 11 additions & 2 deletions cub/cub/device/device_transform.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -17,24 +17,33 @@
#include <cub/device/dispatch/dispatch_transform.cuh>
#include <cub/util_namespace.cuh>

#include <cuda/__functional/address_stability.h>
#include <cuda/std/tuple>

CUB_NAMESPACE_BEGIN

namespace detail
{
template <typename T>
struct __return_constant
{
T value;

THRUST_DEVICE_FUNCTION auto operator()() const -> T
template <typename... Args>
_CCCL_HOST_DEVICE auto operator()(Args&&...) const -> T
{
return value;
}
};
} // namespace detail
CUB_NAMESPACE_END

_CCCL_BEGIN_NAMESPACE_CUDA
template <typename T>
struct proclaims_copyable_arguments<CUB_NS_QUALIFIER::detail::__return_constant<T>> : ::cuda::std::true_type

@fbusato fbusato Sep 19, 2025

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can we use cub::detail:: instead?

@bernhardmgruber bernhardmgruber Sep 19, 2025

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I don't think so. If the user uses a wrapped namespace for cub, then __return_constant would live in user_defined_ns::cub::detail. Since we are completely outside this namespace, lookup would not find it.

{};
_CCCL_END_NAMESPACE_CUDA

CUB_NAMESPACE_BEGIN
//! DeviceTransform provides device-wide, parallel operations for transforming elements tuple-wise from multiple input
//! sequences into an output sequence.
struct DeviceTransform
Expand Down
39 changes: 37 additions & 2 deletions thrust/thrust/detail/internal_functional.h
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@
#include <thrust/iterator/iterator_traits.h>
#include <thrust/tuple.h>

#include <cuda/__functional/address_stability.h>
#include <cuda/__iterator/discard_iterator.h>
#include <cuda/__iterator/tabulate_output_iterator.h>
#include <cuda/__iterator/transform_input_output_iterator.h>
Expand Down Expand Up @@ -92,6 +93,25 @@ struct tuple_binary_predicate
mutable Predicate pred;
};

template <class Predicate, class NewType, class OutputType>
struct new_value_if_f
{
Predicate pred;
NewType new_value;

template <class T>
_CCCL_DEVICE_API OutputType operator()(T const& x)
{
return pred(x) ? new_value : x;
}

template <class T, class P>
_CCCL_DEVICE_API OutputType operator()(T const& x, P const& y)
{
return pred(y) ? new_value : x;
}
};

// We need to mark proxy iterators as such
template <>
inline constexpr bool is_proxy_reference_v<::cuda::discard_iterator::__discard_proxy> = true;
Expand Down Expand Up @@ -287,7 +307,22 @@ struct compare_first
return comp(thrust::raw_reference_cast(::cuda::std::get<0>(x)), thrust::raw_reference_cast(::cuda::std::get<0>(y)));
}
}; // end compare_first

} // end namespace detail

THRUST_NAMESPACE_END

_CCCL_BEGIN_NAMESPACE_CUDA
template <typename Predicate, typename IntegralType>
struct proclaims_copyable_arguments<THRUST_NS_QUALIFIER::detail::predicate_to_integral<Predicate, IntegralType>>
: proclaims_copyable_arguments<Predicate>
{};

template <typename Predicate>
struct proclaims_copyable_arguments<THRUST_NS_QUALIFIER::detail::tuple_binary_predicate<Predicate>>
: proclaims_copyable_arguments<Predicate>
{};

template <class Predicate, class NewType, class OutputType>
struct proclaims_copyable_arguments<THRUST_NS_QUALIFIER::detail::new_value_if_f<Predicate, NewType, OutputType>>
: proclaims_copyable_arguments<Predicate>
{};
_CCCL_END_NAMESPACE_CUDA
54 changes: 12 additions & 42 deletions thrust/thrust/system/cuda/detail/replace.h
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Original file line number Diff line number Diff line change
Expand Up @@ -43,55 +43,24 @@
THRUST_NAMESPACE_BEGIN
namespace cuda_cub
{

namespace __replace
{
template <class T>
struct constant_f
{
T value;

template <class U>
THRUST_DEVICE_FUNCTION T operator()(U const&) const
{
return value;
}
};

template <class Predicate, class NewType, class OutputType>
struct new_value_if_f
{
Predicate pred;
NewType new_value;

template <class T>
OutputType THRUST_DEVICE_FUNCTION operator()(T const& x)
{
return pred(x) ? new_value : x;
}

template <class T, class P>
OutputType THRUST_DEVICE_FUNCTION operator()(T const& x, P const& y)
{
return pred(y) ? new_value : x;
}
};

} // namespace __replace

template <class Derived, class Iterator, class T>
void _CCCL_HOST_DEVICE
replace(execution_policy<Derived>& policy, Iterator first, Iterator last, T const& old_value, T const& new_value)
{
using thrust::placeholders::_1;
cuda_cub::transform_if(policy, first, last, first, __replace::constant_f<T>{new_value}, _1 == old_value);
cuda_cub::transform_if(
policy,
first,
last,
first,
CUB_NS_QUALIFIER::detail::__return_constant<T>{new_value},
thrust::detail::equal_to_value<T>{old_value});
}

template <class Derived, class Iterator, class Predicate, class T>
void _CCCL_HOST_DEVICE
replace_if(execution_policy<Derived>& policy, Iterator first, Iterator last, Predicate pred, T const& new_value)
{
cuda_cub::transform_if(policy, first, last, first, __replace::constant_f<T>{new_value}, pred);
cuda_cub::transform_if(policy, first, last, first, CUB_NS_QUALIFIER::detail::__return_constant<T>{new_value}, pred);
}

template <class Derived, class Iterator, class StencilIt, class Predicate, class T>
Expand All @@ -103,7 +72,8 @@ void _CCCL_HOST_DEVICE replace_if(
Predicate pred,
T const& new_value)
{
cuda_cub::transform_if(policy, first, last, stencil, first, __replace::constant_f<T>{new_value}, pred);
cuda_cub::transform_if(
policy, first, last, stencil, first, CUB_NS_QUALIFIER::detail::__return_constant<T>{new_value}, pred);
}

template <class Derived, class InputIt, class OutputIt, class Predicate, class T>
Expand All @@ -116,7 +86,7 @@ OutputIt _CCCL_HOST_DEVICE replace_copy_if(
T const& new_value)
{
using output_type = thrust::detail::it_value_t<OutputIt>;
using new_value_if_t = __replace::new_value_if_f<Predicate, T, output_type>;
using new_value_if_t = thrust::detail::new_value_if_f<Predicate, T, output_type>;
return cuda_cub::transform(policy, first, last, result, new_value_if_t{predicate, new_value});
}

Expand All @@ -131,7 +101,7 @@ OutputIt _CCCL_HOST_DEVICE replace_copy_if(
T const& new_value)
{
using output_type = thrust::detail::it_value_t<OutputIt>;
using new_value_if_t = __replace::new_value_if_f<Predicate, T, output_type>;
using new_value_if_t = thrust::detail::new_value_if_f<Predicate, T, output_type>;
return cuda_cub::transform(policy, first, last, stencil, result, new_value_if_t{predicate, new_value});
}

Expand Down