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project_6/cccl_upstream/cub/cub/detail/choose_offset.cuh
EngineX CI 56fd68e7dd [INFRA] Import NVIDIA/CCCL upstream as optimization reference library
CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0
2026-07-30 09:35:51 +00:00

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// SPDX-FileCopyrightText: Copyright (c) 2011-2024, NVIDIA CORPORATION. All rights reserved.
// SPDX-License-Identifier: BSD-3
#pragma once
#include <cub/config.cuh>
#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
# pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
# pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
# pragma system_header
#endif // no system header
#include <cuda/std/__iterator/iterator_traits.h>
#include <cuda/std/__type_traits/common_type.h>
#include <cuda/std/__type_traits/conditional.h>
#include <cuda/std/__type_traits/is_integral.h>
#include <cuda/std/__type_traits/is_same.h>
#include <cuda/std/__type_traits/is_unsigned.h>
#include <cuda/std/__type_traits/remove_cv.h>
#include <cuda/std/cstdint>
#include <cuda/std/limits>
CUB_NAMESPACE_BEGIN
namespace detail
{
/**
* choose_offset checks NumItemsT, the type of the num_items parameter, and
* selects the offset type based on it.
*/
template <typename NumItemsT>
struct choose_offset
{
// NumItemsT must be an integral type (but not bool).
static_assert(::cuda::std::is_integral_v<NumItemsT>
&& !::cuda::std::is_same_v<::cuda::std::remove_cv_t<NumItemsT>, bool>,
"NumItemsT must be an integral type, but not bool");
// Unsigned integer type for global offsets.
using type = ::cuda::std::_If<(sizeof(NumItemsT) <= 4), uint32_t, unsigned long long>;
};
/**
* choose_offset_t is an alias template that checks NumItemsT, the type of the num_items parameter, and
* selects the offset type based on it.
*/
template <typename NumItemsT>
using choose_offset_t = typename choose_offset<NumItemsT>::type;
/**
* promote_small_offset checks NumItemsT, the type of the num_items parameter, and
* promotes any integral type smaller than 32 bits to a signed 32-bit integer type.
*/
template <typename NumItemsT>
struct promote_small_offset
{
// NumItemsT must be an integral type (but not bool).
static_assert(::cuda::std::is_integral_v<NumItemsT>
&& !::cuda::std::is_same_v<::cuda::std::remove_cv_t<NumItemsT>, bool>,
"NumItemsT must be an integral type, but not bool");
// Unsigned integer type for global offsets.
using type = ::cuda::std::_If<(sizeof(NumItemsT) < 4), int32_t, NumItemsT>;
};
/**
* promote_small_offset_t is an alias template that checks NumItemsT, the type of the num_items parameter, and
* promotes any integral type smaller than 32 bits to a signed 32-bit integer type.
*/
template <typename NumItemsT>
using promote_small_offset_t = typename promote_small_offset<NumItemsT>::type;
/**
* choose_signed_offset checks NumItemsT, the type of the num_items parameter, and
* selects the offset type to be either int32 or int64, such that the selected offset type covers the range of NumItemsT
* unless it was uint64, in which case int64 will be used.
*/
template <typename NumItemsT>
struct choose_signed_offset
{
// NumItemsT must be an integral type (but not bool).
static_assert(::cuda::std::is_integral_v<NumItemsT>
&& !::cuda::std::is_same_v<::cuda::std::remove_cv_t<NumItemsT>, bool>,
"NumItemsT must be an integral type, but not bool");
// Signed integer type for global offsets.
// uint32 -> int64, else
// LEQ 4B -> int32, else
// int64
using type = ::cuda::std::_If<(::cuda::std::is_integral_v<NumItemsT> && ::cuda::std::is_unsigned_v<NumItemsT>),
::cuda::std::int64_t,
::cuda::std::_If<(sizeof(NumItemsT) <= 4), ::cuda::std::int32_t, ::cuda::std::int64_t>>;
/**
* Checks if the given num_items can be covered by the selected offset type. If not, returns cudaErrorInvalidValue,
* otherwise returns cudaSuccess.
*/
static _CCCL_HOST_DEVICE _CCCL_FORCEINLINE cudaError_t is_exceeding_offset_type(NumItemsT num_items)
{
_CCCL_DIAG_PUSH
_CCCL_DIAG_SUPPRESS_MSVC(4127) /* conditional expression is constant */
if (sizeof(NumItemsT) >= 8 && num_items > static_cast<NumItemsT>(::cuda::std::numeric_limits<type>::max()))
{
return cudaErrorInvalidValue;
}
_CCCL_DIAG_POP
return cudaSuccess;
}
};
/**
* choose_signed_offset_t is an alias template that checks NumItemsT, the type of the num_items parameter, and
* selects the corresponding signed offset type based on it.
*/
template <typename NumItemsT>
using choose_signed_offset_t = typename choose_signed_offset<NumItemsT>::type;
/**
* common_iterator_value sets member type to the common_type of
* value_type for all argument types. used to get OffsetT in
* DeviceSegmentedReduce.
*/
template <typename... Iter>
struct common_iterator_value
{
using type = ::cuda::std::common_type_t<::cuda::std::__iter_value_type<Iter>...>;
};
template <typename... Iter>
using common_iterator_value_t = typename common_iterator_value<Iter...>::type;
} // namespace detail
CUB_NAMESPACE_END