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thread_scan.cuh
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/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
* Copyright (c) 2011-2013, NVIDIA CORPORATION. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the NVIDIA CORPORATION nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************/
/**
* \file
* Thread utilities for sequential prefix scan over statically-sized array types
*/
#pragma once
#include "../thread/thread_operators.cuh"
#include "../util_namespace.cuh"
/// Optional outer namespace(s)
CUB_NS_PREFIX
/// CUB namespace
namespace cub {
/**
* \addtogroup ThreadModule
* @{
*/
/**
* \name Sequential prefix scan over statically-sized array types
* @{
*/
/**
* \brief Perform a sequential exclusive prefix scan over \p LENGTH elements of the \p input array, seeded with the specified \p prefix. The aggregate is returned.
*
* \tparam LENGTH Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanExclusive(
T *input, ///< [in] Input array
T *output, ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op, ///< [in] Binary scan operator
T prefix, ///< [in] Prefix to seed scan with
bool apply_prefix = true) ///< [in] Whether or not the calling thread should apply its prefix. If not, the first output element is undefined. (Handy for preventing thread-0 from applying a prefix.)
{
T inclusive = input[0];
if (apply_prefix)
{
inclusive = scan_op(prefix, inclusive);
}
output[0] = prefix;
T exclusive = inclusive;
#pragma unroll
for (int i = 1; i < LENGTH; ++i)
{
inclusive = scan_op(exclusive, input[i]);
output[i] = exclusive;
exclusive = inclusive;
}
return inclusive;
}
/**
* \brief Perform a sequential exclusive prefix scan over the statically-sized \p input array, seeded with the specified \p prefix. The aggregate is returned.
*
* \tparam LENGTH <b>[inferred]</b> Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanExclusive(
T (&input)[LENGTH], ///< [in] Input array
T (&output)[LENGTH], ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op, ///< [in] Binary scan operator
T prefix, ///< [in] Prefix to seed scan with
bool apply_prefix = true) ///< [in] Whether or not the calling thread should apply its prefix. (Handy for preventing thread-0 from applying a prefix.)
{
return ThreadScanExclusive<LENGTH>((T*) input, (T*) output, scan_op, prefix);
}
/**
* \brief Perform a sequential inclusive prefix scan over \p LENGTH elements of the \p input array. The aggregate is returned.
*
* \tparam LENGTH Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanInclusive(
T *input, ///< [in] Input array
T *output, ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op) ///< [in] Binary scan operator
{
T inclusive = input[0];
output[0] = inclusive;
// Continue scan
#pragma unroll
for (int i = 0; i < LENGTH; ++i)
{
inclusive = scan_op(inclusive, input[i]);
output[i] = inclusive;
}
return inclusive;
}
/**
* \brief Perform a sequential inclusive prefix scan over the statically-sized \p input array. The aggregate is returned.
*
* \tparam LENGTH <b>[inferred]</b> Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanInclusive(
T (&input)[LENGTH], ///< [in] Input array
T (&output)[LENGTH], ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op) ///< [in] Binary scan operator
{
return ThreadScanInclusive<LENGTH>((T*) input, (T*) output, scan_op);
}
/**
* \brief Perform a sequential inclusive prefix scan over \p LENGTH elements of the \p input array, seeded with the specified \p prefix. The aggregate is returned.
*
* \tparam LENGTH Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanInclusive(
T *input, ///< [in] Input array
T *output, ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op, ///< [in] Binary scan operator
T prefix, ///< [in] Prefix to seed scan with
bool apply_prefix = true) ///< [in] Whether or not the calling thread should apply its prefix. (Handy for preventing thread-0 from applying a prefix.)
{
T inclusive = input[0];
if (apply_prefix)
{
inclusive = scan_op(prefix, inclusive);
}
output[0] = inclusive;
// Continue scan
#pragma unroll
for (int i = 1; i < LENGTH; ++i)
{
inclusive = scan_op(inclusive, input[i]);
output[i] = inclusive;
}
return inclusive;
}
/**
* \brief Perform a sequential inclusive prefix scan over the statically-sized \p input array, seeded with the specified \p prefix. The aggregate is returned.
*
* \tparam LENGTH <b>[inferred]</b> Length of \p input and \p output arrays
* \tparam T <b>[inferred]</b> The data type to be scanned.
* \tparam ScanOp <b>[inferred]</b> Binary scan operator type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
int LENGTH,
typename T,
typename ScanOp>
__device__ __forceinline__ T ThreadScanInclusive(
T (&input)[LENGTH], ///< [in] Input array
T (&output)[LENGTH], ///< [out] Output array (may be aliased to \p input)
ScanOp scan_op, ///< [in] Binary scan operator
T prefix, ///< [in] Prefix to seed scan with
bool apply_prefix = true) ///< [in] Whether or not the calling thread should apply its prefix. (Handy for preventing thread-0 from applying a prefix.)
{
return ThreadScanInclusive<LENGTH>((T*) input, (T*) output, scan_op, prefix, apply_prefix);
}
//@} end member group
/** @} */ // end group ThreadModule
} // CUB namespace
CUB_NS_POSTFIX // Optional outer namespace(s)

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