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/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
* Copyright (c) 2011-2018, 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
* cub::DeviceReduce provides device-wide, parallel operations for computing a reduction across a sequence of data items residing within device-accessible memory.
*/
#pragma once
#include <stdio.h>
#include <iterator>
#include <limits>
#include "../iterator/arg_index_input_iterator.cuh"
#include "dispatch/dispatch_reduce.cuh"
#include "dispatch/dispatch_reduce_by_key.cuh"
#include "../config.cuh"
/// Optional outer namespace(s)
CUB_NS_PREFIX
/// CUB namespace
namespace cub {
/**
* \brief DeviceReduce provides device-wide, parallel operations for computing a reduction across a sequence of data items residing within device-accessible memory. 
* \ingroup SingleModule
*
* \par Overview
* A <a href="http://en.wikipedia.org/wiki/Reduce_(higher-order_function)"><em>reduction</em></a> (or <em>fold</em>)
* uses a binary combining operator to compute a single aggregate from a sequence of input elements.
*
* \par Usage Considerations
* \cdp_class{DeviceReduce}
*
* \par Performance
* \linear_performance{reduction, reduce-by-key, and run-length encode}
*
* \par
* The following chart illustrates DeviceReduce::Sum
* performance across different CUDA architectures for \p int32 keys.
*
* \image html reduce_int32.png
*
* \par
* The following chart illustrates DeviceReduce::ReduceByKey (summation)
* performance across different CUDA architectures for \p fp32
* values. Segments are identified by \p int32 keys, and have lengths uniformly sampled from [1,1000].
*
* \image html reduce_by_key_fp32_len_500.png
*
* \par
* \plots_below
*
*/
struct DeviceReduce
{
/**
* \brief Computes a device-wide reduction using the specified binary \p reduction_op functor and initial value \p init.
*
* \par
* - Does not support binary reduction operators that are non-commutative.
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Snippet
* The code snippet below illustrates a user-defined min-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_radix_sort.cuh>
*
* // CustomMin functor
* struct CustomMin
* {
* template <typename T>
* __device__ __forceinline__
* T operator()(const T &a, const T &b) const {
* return (b < a) ? b : a;
* }
* };
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* int *d_out; // e.g., [-]
* CustomMin min_op;
* int init; // e.g., INT_MAX
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::Reduce(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items, min_op, init);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run reduction
* cub::DeviceReduce::Reduce(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items, min_op, init);
*
* // d_out <-- [0]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate \iterator
* \tparam ReductionOpT <b>[inferred]</b> Binary reduction functor type having member <tt>T operator()(const T &a, const T &b)</tt>
* \tparam T <b>[inferred]</b> Data element type that is convertible to the \p value type of \p InputIteratorT
*/
template <
typename InputIteratorT,
typename OutputIteratorT,
typename ReductionOpT,
typename T>
CUB_RUNTIME_FUNCTION
static cudaError_t Reduce(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
ReductionOpT reduction_op, ///< [in] Binary reduction functor
T init, ///< [in] Initial value of the reduction
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
return DispatchReduce<InputIteratorT, OutputIteratorT, OffsetT, ReductionOpT>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_in,
d_out,
num_items,
reduction_op,
init,
stream,
debug_synchronous);
}
/**
* \brief Computes a device-wide sum using the addition (\p +) operator.
*
* \par
* - Uses \p 0 as the initial value of the reduction.
* - Does not support \p + operators that are non-commutative..
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Performance
* The following charts illustrate saturated sum-reduction performance across different
* CUDA architectures for \p int32 and \p int64 items, respectively.
*
* \image html reduce_int32.png
* \image html reduce_int64.png
*
* \par Snippet
* The code snippet below illustrates the sum-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_radix_sort.cuh>
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* int *d_out; // e.g., [-]
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::Sum(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run sum-reduction
* cub::DeviceReduce::Sum(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items);
*
* // d_out <-- [38]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate \iterator
*/
template <
typename InputIteratorT,
typename OutputIteratorT>
CUB_RUNTIME_FUNCTION
static cudaError_t Sum(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// The output value type
typedef typename If<(Equals<typename std::iterator_traits<OutputIteratorT>::value_type, void>::VALUE), // OutputT = (if output iterator's value type is void) ?
typename std::iterator_traits<InputIteratorT>::value_type, // ... then the input iterator's value type,
typename std::iterator_traits<OutputIteratorT>::value_type>::Type OutputT; // ... else the output iterator's value type
return DispatchReduce<InputIteratorT, OutputIteratorT, OffsetT, cub::Sum>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_in,
d_out,
num_items,
cub::Sum(),
OutputT(), // zero-initialize
stream,
debug_synchronous);
}
/**
* \brief Computes a device-wide minimum using the less-than ('<') operator.
*
* \par
* - Uses <tt>std::numeric_limits<T>::max()</tt> as the initial value of the reduction.
* - Does not support \p < operators that are non-commutative.
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Snippet
* The code snippet below illustrates the min-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_radix_sort.cuh>
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* int *d_out; // e.g., [-]
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::Min(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run min-reduction
* cub::DeviceReduce::Min(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items);
*
* // d_out <-- [0]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate \iterator
*/
template <
typename InputIteratorT,
typename OutputIteratorT>
CUB_RUNTIME_FUNCTION
static cudaError_t Min(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// The input value type
typedef typename std::iterator_traits<InputIteratorT>::value_type InputT;
return DispatchReduce<InputIteratorT, OutputIteratorT, OffsetT, cub::Min>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_in,
d_out,
num_items,
cub::Min(),
Traits<InputT>::Max(), // replace with std::numeric_limits<T>::max() when C++11 support is more prevalent
stream,
debug_synchronous);
}
/**
* \brief Finds the first device-wide minimum using the less-than ('<') operator, also returning the index of that item.
*
* \par
* - The output value type of \p d_out is cub::KeyValuePair <tt><int, T></tt> (assuming the value type of \p d_in is \p T)
* - The minimum is written to <tt>d_out.value</tt> and its offset in the input array is written to <tt>d_out.key</tt>.
* - The <tt>{1, std::numeric_limits<T>::max()}</tt> tuple is produced for zero-length inputs
* - Does not support \p < operators that are non-commutative.
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Snippet
* The code snippet below illustrates the argmin-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_radix_sort.cuh>
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* KeyValuePair<int, int> *d_out; // e.g., [{-,-}]
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::ArgMin(d_temp_storage, temp_storage_bytes, d_in, d_argmin, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run argmin-reduction
* cub::DeviceReduce::ArgMin(d_temp_storage, temp_storage_bytes, d_in, d_argmin, num_items);
*
* // d_out <-- [{5, 0}]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items (of some type \p T) \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate (having value type <tt>cub::KeyValuePair<int, T></tt>) \iterator
*/
template <
typename InputIteratorT,
typename OutputIteratorT>
CUB_RUNTIME_FUNCTION
static cudaError_t ArgMin(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// The input type
typedef typename std::iterator_traits<InputIteratorT>::value_type InputValueT;
// The output tuple type
typedef typename If<(Equals<typename std::iterator_traits<OutputIteratorT>::value_type, void>::VALUE), // OutputT = (if output iterator's value type is void) ?
KeyValuePair<OffsetT, InputValueT>, // ... then the key value pair OffsetT + InputValueT
typename std::iterator_traits<OutputIteratorT>::value_type>::Type OutputTupleT; // ... else the output iterator's value type
// The output value type
typedef typename OutputTupleT::Value OutputValueT;
// Wrapped input iterator to produce index-value <OffsetT, InputT> tuples
typedef ArgIndexInputIterator<InputIteratorT, OffsetT, OutputValueT> ArgIndexInputIteratorT;
ArgIndexInputIteratorT d_indexed_in(d_in);
// Initial value
OutputTupleT initial_value(1, Traits<InputValueT>::Max()); // replace with std::numeric_limits<T>::max() when C++11 support is more prevalent
return DispatchReduce<ArgIndexInputIteratorT, OutputIteratorT, OffsetT, cub::ArgMin>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_indexed_in,
d_out,
num_items,
cub::ArgMin(),
initial_value,
stream,
debug_synchronous);
}
/**
* \brief Computes a device-wide maximum using the greater-than ('>') operator.
*
* \par
* - Uses <tt>std::numeric_limits<T>::lowest()</tt> as the initial value of the reduction.
* - Does not support \p > operators that are non-commutative.
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Snippet
* The code snippet below illustrates the max-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_radix_sort.cuh>
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* int *d_out; // e.g., [-]
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::Max(d_temp_storage, temp_storage_bytes, d_in, d_max, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run max-reduction
* cub::DeviceReduce::Max(d_temp_storage, temp_storage_bytes, d_in, d_max, num_items);
*
* // d_out <-- [9]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate \iterator
*/
template <
typename InputIteratorT,
typename OutputIteratorT>
CUB_RUNTIME_FUNCTION
static cudaError_t Max(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// The input value type
typedef typename std::iterator_traits<InputIteratorT>::value_type InputT;
return DispatchReduce<InputIteratorT, OutputIteratorT, OffsetT, cub::Max>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_in,
d_out,
num_items,
cub::Max(),
Traits<InputT>::Lowest(), // replace with std::numeric_limits<T>::lowest() when C++11 support is more prevalent
stream,
debug_synchronous);
}
/**
* \brief Finds the first device-wide maximum using the greater-than ('>') operator, also returning the index of that item
*
* \par
* - The output value type of \p d_out is cub::KeyValuePair <tt><int, T></tt> (assuming the value type of \p d_in is \p T)
* - The maximum is written to <tt>d_out.value</tt> and its offset in the input array is written to <tt>d_out.key</tt>.
* - The <tt>{1, std::numeric_limits<T>::lowest()}</tt> tuple is produced for zero-length inputs
* - Does not support \p > operators that are non-commutative.
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Snippet
* The code snippet below illustrates the argmax-reduction of a device vector of \p int data elements.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_reduce.cuh>
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 7
* int *d_in; // e.g., [8, 6, 7, 5, 3, 0, 9]
* KeyValuePair<int, int> *d_out; // e.g., [{-,-}]
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::ArgMax(d_temp_storage, temp_storage_bytes, d_in, d_argmax, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run argmax-reduction
* cub::DeviceReduce::ArgMax(d_temp_storage, temp_storage_bytes, d_in, d_argmax, num_items);
*
* // d_out <-- [{6, 9}]
*
* \endcode
*
* \tparam InputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input items (of some type \p T) \iterator
* \tparam OutputIteratorT <b>[inferred]</b> Output iterator type for recording the reduced aggregate (having value type <tt>cub::KeyValuePair<int, T></tt>) \iterator
*/
template <
typename InputIteratorT,
typename OutputIteratorT>
CUB_RUNTIME_FUNCTION
static cudaError_t ArgMax(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
InputIteratorT d_in, ///< [in] Pointer to the input sequence of data items
OutputIteratorT d_out, ///< [out] Pointer to the output aggregate
int num_items, ///< [in] Total number of input items (i.e., length of \p d_in)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. Also causes launch configurations to be printed to the console. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// The input type
typedef typename std::iterator_traits<InputIteratorT>::value_type InputValueT;
// The output tuple type
typedef typename If<(Equals<typename std::iterator_traits<OutputIteratorT>::value_type, void>::VALUE), // OutputT = (if output iterator's value type is void) ?
KeyValuePair<OffsetT, InputValueT>, // ... then the key value pair OffsetT + InputValueT
typename std::iterator_traits<OutputIteratorT>::value_type>::Type OutputTupleT; // ... else the output iterator's value type
// The output value type
typedef typename OutputTupleT::Value OutputValueT;
// Wrapped input iterator to produce index-value <OffsetT, InputT> tuples
typedef ArgIndexInputIterator<InputIteratorT, OffsetT, OutputValueT> ArgIndexInputIteratorT;
ArgIndexInputIteratorT d_indexed_in(d_in);
// Initial value
OutputTupleT initial_value(1, Traits<InputValueT>::Lowest()); // replace with std::numeric_limits<T>::lowest() when C++11 support is more prevalent
return DispatchReduce<ArgIndexInputIteratorT, OutputIteratorT, OffsetT, cub::ArgMax>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_indexed_in,
d_out,
num_items,
cub::ArgMax(),
initial_value,
stream,
debug_synchronous);
}
/**
* \brief Reduces segments of values, where segments are demarcated by corresponding runs of identical keys.
*
* \par
* This operation computes segmented reductions within \p d_values_in using
* the specified binary \p reduction_op functor. The segments are identified by
* "runs" of corresponding keys in \p d_keys_in, where runs are maximal ranges of
* consecutive, identical keys. For the <em>i</em><sup>th</sup> run encountered,
* the first key of the run and the corresponding value aggregate of that run are
* written to <tt>d_unique_out[<em>i</em>]</tt> and <tt>d_aggregates_out[<em>i</em>]</tt>,
* respectively. The total number of runs encountered is written to \p d_num_runs_out.
*
* \par
* - The <tt>==</tt> equality operator is used to determine whether keys are equivalent
* - Provides "run-to-run" determinism for pseudo-associative reduction
* (e.g., addition of floating point types) on the same GPU device.
* However, results for pseudo-associative reduction may be inconsistent
* from one device to a another device of a different compute-capability
* because CUB can employ different tile-sizing for different architectures.
* - \devicestorage
*
* \par Performance
* The following chart illustrates reduction-by-key (sum) performance across
* different CUDA architectures for \p fp32 and \p fp64 values, respectively. Segments
* are identified by \p int32 keys, and have lengths uniformly sampled from [1,1000].
*
* \image html reduce_by_key_fp32_len_500.png
* \image html reduce_by_key_fp64_len_500.png
*
* \par
* The following charts are similar, but with segment lengths uniformly sampled from [1,10]:
*
* \image html reduce_by_key_fp32_len_5.png
* \image html reduce_by_key_fp64_len_5.png
*
* \par Snippet
* The code snippet below illustrates the segmented reduction of \p int values grouped
* by runs of associated \p int keys.
* \par
* \code
* #include <cub/cub.cuh> // or equivalently <cub/device/device_reduce.cuh>
*
* // CustomMin functor
* struct CustomMin
* {
* template <typename T>
* CUB_RUNTIME_FUNCTION __forceinline__
* T operator()(const T &a, const T &b) const {
* return (b < a) ? b : a;
* }
* };
*
* // Declare, allocate, and initialize device-accessible pointers for input and output
* int num_items; // e.g., 8
* int *d_keys_in; // e.g., [0, 2, 2, 9, 5, 5, 5, 8]
* int *d_values_in; // e.g., [0, 7, 1, 6, 2, 5, 3, 4]
* int *d_unique_out; // e.g., [-, -, -, -, -, -, -, -]
* int *d_aggregates_out; // e.g., [-, -, -, -, -, -, -, -]
* int *d_num_runs_out; // e.g., [-]
* CustomMin reduction_op;
* ...
*
* // Determine temporary device storage requirements
* void *d_temp_storage = NULL;
* size_t temp_storage_bytes = 0;
* cub::DeviceReduce::ReduceByKey(d_temp_storage, temp_storage_bytes, d_keys_in, d_unique_out, d_values_in, d_aggregates_out, d_num_runs_out, reduction_op, num_items);
*
* // Allocate temporary storage
* cudaMalloc(&d_temp_storage, temp_storage_bytes);
*
* // Run reduce-by-key
* cub::DeviceReduce::ReduceByKey(d_temp_storage, temp_storage_bytes, d_keys_in, d_unique_out, d_values_in, d_aggregates_out, d_num_runs_out, reduction_op, num_items);
*
* // d_unique_out <-- [0, 2, 9, 5, 8]
* // d_aggregates_out <-- [0, 1, 6, 2, 4]
* // d_num_runs_out <-- [5]
*
* \endcode
*
* \tparam KeysInputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input keys \iterator
* \tparam UniqueOutputIteratorT <b>[inferred]</b> Random-access output iterator type for writing unique output keys \iterator
* \tparam ValuesInputIteratorT <b>[inferred]</b> Random-access input iterator type for reading input values \iterator
* \tparam AggregatesOutputIterator <b>[inferred]</b> Random-access output iterator type for writing output value aggregates \iterator
* \tparam NumRunsOutputIteratorT <b>[inferred]</b> Output iterator type for recording the number of runs encountered \iterator
* \tparam ReductionOpT <b>[inferred]</b> Binary reduction functor type having member <tt>T operator()(const T &a, const T &b)</tt>
*/
template <
typename KeysInputIteratorT,
typename UniqueOutputIteratorT,
typename ValuesInputIteratorT,
typename AggregatesOutputIteratorT,
typename NumRunsOutputIteratorT,
typename ReductionOpT>
CUB_RUNTIME_FUNCTION __forceinline__
static cudaError_t ReduceByKey(
void *d_temp_storage, ///< [in] %Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
size_t &temp_storage_bytes, ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
KeysInputIteratorT d_keys_in, ///< [in] Pointer to the input sequence of keys
UniqueOutputIteratorT d_unique_out, ///< [out] Pointer to the output sequence of unique keys (one key per run)
ValuesInputIteratorT d_values_in, ///< [in] Pointer to the input sequence of corresponding values
AggregatesOutputIteratorT d_aggregates_out, ///< [out] Pointer to the output sequence of value aggregates (one aggregate per run)
NumRunsOutputIteratorT d_num_runs_out, ///< [out] Pointer to total number of runs encountered (i.e., the length of d_unique_out)
ReductionOpT reduction_op, ///< [in] Binary reduction functor
int num_items, ///< [in] Total number of associated key+value pairs (i.e., the length of \p d_in_keys and \p d_in_values)
cudaStream_t stream = 0, ///< [in] <b>[optional]</b> CUDA stream to launch kernels within. Default is stream<sub>0</sub>.
bool debug_synchronous = false) ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors. May cause significant slowdown. Default is \p false.
{
// Signed integer type for global offsets
typedef int OffsetT;
// FlagT iterator type (not used)
// Selection op (not used)
// Default == operator
typedef Equality EqualityOp;
return DispatchReduceByKey<KeysInputIteratorT, UniqueOutputIteratorT, ValuesInputIteratorT, AggregatesOutputIteratorT, NumRunsOutputIteratorT, EqualityOp, ReductionOpT, OffsetT>::Dispatch(
d_temp_storage,
temp_storage_bytes,
d_keys_in,
d_unique_out,
d_values_in,
d_aggregates_out,
d_num_runs_out,
EqualityOp(),
reduction_op,
num_items,
stream,
debug_synchronous);
}
};
/**
* \example example_device_reduce.cu
*/
} // CUB namespace
CUB_NS_POSTFIX // Optional outer namespace(s)
|