Detailed description

DeviceSegmentedRadixSort provides device-wide, parallel operations for computing a batched radix sort across multiple, non-overlapping sequences of data items residing within device-accessible memory.

.

Overview: The radix sorting method arranges items into ascending (or descending) order. The algorithm relies upon a positional representation for keys, i.e., each key is comprised of an ordered sequence of symbols (e.g., digits, characters, etc.) specified from least-significant to most-significant. For a given input sequence of keys and a set of rules specifying a total ordering of the symbolic alphabet, the radix sorting method produces a lexicographic ordering of those keys.

See Also: DeviceSegmentedRadixSort shares its implementation with DeviceRadixSort. See that algorithm's documentation for more information.

Usage Considerations

Dynamic parallelism. DeviceSegmentedRadixSort methods can be called within kernel code on devices in which CUDA dynamic parallelism is supported.

Static Public Methods
Key-value pairs
template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortPairs (void d_temp_storage, size_t &temp_storage_bytes, const KeyT d_keys_in, KeyT d_keys_out, const ValueT d_values_in, ValueT d_values_out, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of key-value pairs into ascending order. (~2N auxiliary storage required) More...

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortPairs (void d_temp_storage, size_t &temp_storage_bytes, DoubleBuffer< KeyT > &d_keys, DoubleBuffer< ValueT > &d_values, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of key-value pairs into ascending order. (~N auxiliary storage required) More...

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortPairsDescending (void d_temp_storage, size_t &temp_storage_bytes, const KeyT d_keys_in, KeyT d_keys_out, const ValueT d_values_in, ValueT d_values_out, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of key-value pairs into descending order. (~2N auxiliary storage required). More...

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortPairsDescending (void d_temp_storage, size_t &temp_storage_bytes, DoubleBuffer< KeyT > &d_keys, DoubleBuffer< ValueT > &d_values, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of key-value pairs into descending order. (~N auxiliary storage required). More...

Keys-only
template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortKeys (void d_temp_storage, size_t &temp_storage_bytes, const KeyT d_keys_in, KeyT d_keys_out, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of keys into ascending order. (~2N auxiliary storage required) More...

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortKeys (void d_temp_storage, size_t &temp_storage_bytes, DoubleBuffer< KeyT > &d_keys, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of keys into ascending order. (~N auxiliary storage required). More...

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortKeysDescending (void d_temp_storage, size_t &temp_storage_bytes, const KeyT d_keys_in, KeyT d_keys_out, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of keys into descending order. (~2N auxiliary storage required). More...

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >
static CUB_RUNTIME_FUNCTION cudaError_t	SortKeysDescending (void d_temp_storage, size_t &temp_storage_bytes, DoubleBuffer< KeyT > &d_keys, int num_items, int num_segments, BeginOffsetIteratorT d_begin_offsets, EndOffsetIteratorT d_end_offsets, int begin_bit=0, int end_bit=sizeof(KeyT)8, cudaStream_t stream=0, bool debug_synchronous=false)
	Sorts segments of keys into descending order. (~N auxiliary storage required). More...

Member Function Documentation

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortPairs	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		const KeyT *	d_keys_in,
		KeyT *	d_keys_out,
		const ValueT *	d_values_in,
		ValueT *	d_values_out,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of key-value pairs into ascending order. (~2N auxiliary storage required)

The contents of the input data are not altered by the sorting operation
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires an allocation of temporary device storage that is O(N+P), where N is the length of the input and P is the number of streaming multiprocessors on the device. For sorting using only O(P) temporary storage, see the sorting interface using DoubleBuffer wrappers below.
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys with associated vector of int values.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_keys_in; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_keys_out; // e.g., [-, -, -, -, -, -, -]

int *d_values_in; // e.g., [0, 1, 2, 3, 4, 5, 6]

int *d_values_out; // e.g., [-, -, -, -, -, -, -]

...

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortPairs(d_temp_storage, temp_storage_bytes,

d_keys_in, d_keys_out, d_values_in, d_values_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortPairs(d_temp_storage, temp_storage_bytes,

d_keys_in, d_keys_out, d_values_in, d_values_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys_out <-- [6, 7, 8, 0, 3, 5, 9]

// d_values_out <-- [1, 2, 0, 5, 4, 3, 6]

Template Parameters

KeyT	[inferred] Key type
ValueT	[inferred] Value type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in]	d_keys_in	Device-accessible pointer to the input data of key data to sort
[out]	d_keys_out	Device-accessible pointer to the sorted output sequence of key data
[in]	d_values_in	Device-accessible pointer to the corresponding input sequence of associated value items
[out]	d_values_out	Device-accessible pointer to the correspondingly-reordered output sequence of associated value items
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortPairs	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		DoubleBuffer< KeyT > &	d_keys,
		DoubleBuffer< ValueT > &	d_values,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of key-value pairs into ascending order. (~N auxiliary storage required)

The sorting operation is given a pair of key buffers and a corresponding pair of associated value buffers. Each pair is managed by a DoubleBuffer structure that indicates which of the two buffers is "current" (and thus contains the input data to be sorted).
The contents of both buffers within each pair may be altered by the sorting operation.
Upon completion, the sorting operation will update the "current" indicator within each DoubleBuffer wrapper to reference which of the two buffers now contains the sorted output sequence (a function of the number of key bits specified and the targeted device architecture).
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires a relatively small allocation of temporary device storage that is O(P), where P is the number of streaming multiprocessors on the device (and is typically a small constant relative to the input size N).
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys with associated vector of int values.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_key_buf; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_key_alt_buf; // e.g., [-, -, -, -, -, -, -]

int *d_value_buf; // e.g., [0, 1, 2, 3, 4, 5, 6]

int *d_value_alt_buf; // e.g., [-, -, -, -, -, -, -]

...

// Create a set of DoubleBuffers to wrap pairs of device pointers

cub::DoubleBuffer<int> d_keys(d_key_buf, d_key_alt_buf);

cub::DoubleBuffer<int> d_values(d_value_buf, d_value_alt_buf);

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortPairs(d_temp_storage, temp_storage_bytes, d_keys, d_values,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortPairs(d_temp_storage, temp_storage_bytes, d_keys, d_values,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys.Current() <-- [6, 7, 8, 0, 3, 5, 9]

// d_values.Current() <-- [5, 4, 3, 1, 2, 0, 6]

Template Parameters

KeyT	[inferred] Key type
ValueT	[inferred] Value type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in,out]	d_keys	Reference to the double-buffer of keys whose "current" device-accessible buffer contains the unsorted input keys and, upon return, is updated to point to the sorted output keys
[in,out]	d_values	Double-buffer of values whose "current" device-accessible buffer contains the unsorted input values and, upon return, is updated to point to the sorted output values
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortPairsDescending	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		const KeyT *	d_keys_in,
		KeyT *	d_keys_out,
		const ValueT *	d_values_in,
		ValueT *	d_values_out,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of key-value pairs into descending order. (~2N auxiliary storage required).

The contents of the input data are not altered by the sorting operation
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires an allocation of temporary device storage that is O(N+P), where N is the length of the input and P is the number of streaming multiprocessors on the device. For sorting using only O(P) temporary storage, see the sorting interface using DoubleBuffer wrappers below.
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys with associated vector of int values.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_keys_in; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_keys_out; // e.g., [-, -, -, -, -, -, -]

int *d_values_in; // e.g., [0, 1, 2, 3, 4, 5, 6]

int *d_values_out; // e.g., [-, -, -, -, -, -, -]

...

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes,

d_keys_in, d_keys_out, d_values_in, d_values_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes,

d_keys_in, d_keys_out, d_values_in, d_values_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys_out <-- [8, 7, 6, 9, 5, 3, 0]

// d_values_out <-- [0, 2, 1, 6, 3, 4, 5]

Template Parameters

KeyT	[inferred] Key type
ValueT	[inferred] Value type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in]	d_keys_in	Device-accessible pointer to the input data of key data to sort
[out]	d_keys_out	Device-accessible pointer to the sorted output sequence of key data
[in]	d_values_in	Device-accessible pointer to the corresponding input sequence of associated value items
[out]	d_values_out	Device-accessible pointer to the correspondingly-reordered output sequence of associated value items
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename ValueT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortPairsDescending	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		DoubleBuffer< KeyT > &	d_keys,
		DoubleBuffer< ValueT > &	d_values,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of key-value pairs into descending order. (~N auxiliary storage required).

The sorting operation is given a pair of key buffers and a corresponding pair of associated value buffers. Each pair is managed by a DoubleBuffer structure that indicates which of the two buffers is "current" (and thus contains the input data to be sorted).
The contents of both buffers within each pair may be altered by the sorting operation.
Upon completion, the sorting operation will update the "current" indicator within each DoubleBuffer wrapper to reference which of the two buffers now contains the sorted output sequence (a function of the number of key bits specified and the targeted device architecture).
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires a relatively small allocation of temporary device storage that is O(P), where P is the number of streaming multiprocessors on the device (and is typically a small constant relative to the input size N).
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys with associated vector of int values.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_key_buf; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_key_alt_buf; // e.g., [-, -, -, -, -, -, -]

int *d_value_buf; // e.g., [0, 1, 2, 3, 4, 5, 6]

int *d_value_alt_buf; // e.g., [-, -, -, -, -, -, -]

...

// Create a set of DoubleBuffers to wrap pairs of device pointers

cub::DoubleBuffer<int> d_keys(d_key_buf, d_key_alt_buf);

cub::DoubleBuffer<int> d_values(d_value_buf, d_value_alt_buf);

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, d_keys, d_values,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, d_keys, d_values,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys.Current() <-- [8, 7, 6, 9, 5, 3, 0]

// d_values.Current() <-- [0, 2, 1, 6, 3, 4, 5]

Template Parameters

KeyT	[inferred] Key type
ValueT	[inferred] Value type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in,out]	d_keys	Reference to the double-buffer of keys whose "current" device-accessible buffer contains the unsorted input keys and, upon return, is updated to point to the sorted output keys
[in,out]	d_values	Double-buffer of values whose "current" device-accessible buffer contains the unsorted input values and, upon return, is updated to point to the sorted output values
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortKeys	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		const KeyT *	d_keys_in,
		KeyT *	d_keys_out,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of keys into ascending order. (~2N auxiliary storage required)

The contents of the input data are not altered by the sorting operation
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
This operation requires an allocation of temporary device storage that is O(N+P), where N is the length of the input and P is the number of streaming multiprocessors on the device. For sorting using only O(P) temporary storage, see the sorting interface using DoubleBuffer wrappers below.
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_keys_in; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_keys_out; // e.g., [-, -, -, -, -, -, -]

...

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortKeys(d_temp_storage, temp_storage_bytes, d_keys_in, d_keys_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortKeys(d_temp_storage, temp_storage_bytes, d_keys_in, d_keys_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys_out <-- [6, 7, 8, 0, 3, 5, 9]

Template Parameters

KeyT	[inferred] Key type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in]	d_keys_in	Device-accessible pointer to the input data of key data to sort
[out]	d_keys_out	Device-accessible pointer to the sorted output sequence of key data
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortKeys	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		DoubleBuffer< KeyT > &	d_keys,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of keys into ascending order. (~N auxiliary storage required).

The sorting operation is given a pair of key buffers managed by a DoubleBuffer structure that indicates which of the two buffers is "current" (and thus contains the input data to be sorted).
The contents of both buffers may be altered by the sorting operation.
Upon completion, the sorting operation will update the "current" indicator within the DoubleBuffer wrapper to reference which of the two buffers now contains the sorted output sequence (a function of the number of key bits specified and the targeted device architecture).
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires a relatively small allocation of temporary device storage that is O(P), where P is the number of streaming multiprocessors on the device (and is typically a small constant relative to the input size N).
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_key_buf; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_key_alt_buf; // e.g., [-, -, -, -, -, -, -]

...

// Create a DoubleBuffer to wrap the pair of device pointers

cub::DoubleBuffer<int> d_keys(d_key_buf, d_key_alt_buf);

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortKeys(d_temp_storage, temp_storage_bytes, d_keys,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortKeys(d_temp_storage, temp_storage_bytes, d_keys,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys.Current() <-- [6, 7, 8, 0, 3, 5, 9]

Template Parameters

KeyT	[inferred] Key type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in,out]	d_keys	Reference to the double-buffer of keys whose "current" device-accessible buffer contains the unsorted input keys and, upon return, is updated to point to the sorted output keys
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortKeysDescending	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		const KeyT *	d_keys_in,
		KeyT *	d_keys_out,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of keys into descending order. (~2N auxiliary storage required).

The contents of the input data are not altered by the sorting operation
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires an allocation of temporary device storage that is O(N+P), where N is the length of the input and P is the number of streaming multiprocessors on the device. For sorting using only O(P) temporary storage, see the sorting interface using DoubleBuffer wrappers below.
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_keys_in; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_keys_out; // e.g., [-, -, -, -, -, -, -]

...

// Create a DoubleBuffer to wrap the pair of device pointers

cub::DoubleBuffer<int> d_keys(d_key_buf, d_key_alt_buf);

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortKeysDescending(d_temp_storage, temp_storage_bytes, d_keys_in, d_keys_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortKeysDescending(d_temp_storage, temp_storage_bytes, d_keys_in, d_keys_out,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys_out <-- [8, 7, 6, 9, 5, 3, 0]

Template Parameters

KeyT	[inferred] Key type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in]	d_keys_in	Device-accessible pointer to the input data of key data to sort
[out]	d_keys_out	Device-accessible pointer to the sorted output sequence of key data
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

template<typename KeyT , typename BeginOffsetIteratorT , typename EndOffsetIteratorT >

static CUB_RUNTIME_FUNCTION cudaError_t cub::DeviceSegmentedRadixSort::SortKeysDescending	(	void *	d_temp_storage,
		size_t &	temp_storage_bytes,
		DoubleBuffer< KeyT > &	d_keys,
		int	num_items,
		int	num_segments,
		BeginOffsetIteratorT	d_begin_offsets,
		EndOffsetIteratorT	d_end_offsets,
		int	begin_bit = `0`,
		int	end_bit = `sizeof(KeyT) * 8`,
		cudaStream_t	stream = `0`,
		bool	debug_synchronous = `false`
	)

inlinestatic

Sorts segments of keys into descending order. (~N auxiliary storage required).

The sorting operation is given a pair of key buffers managed by a DoubleBuffer structure that indicates which of the two buffers is "current" (and thus contains the input data to be sorted).
The contents of both buffers may be altered by the sorting operation.
Upon completion, the sorting operation will update the "current" indicator within the DoubleBuffer wrapper to reference which of the two buffers now contains the sorted output sequence (a function of the number of key bits specified and the targeted device architecture).
When input a contiguous sequence of segments, a single sequence segment_offsets (of length num_segments+1) can be aliased for both the d_begin_offsets and d_end_offsets parameters (where the latter is specified as segment_offsets+1).
An optional bit subrange [begin_bit, end_bit) of differentiating key bits can be specified. This can reduce overall sorting overhead and yield a corresponding performance improvement.
This operation requires a relatively small allocation of temporary device storage that is O(P), where P is the number of streaming multiprocessors on the device (and is typically a small constant relative to the input size N).
When d_temp_storage is NULL, no work is done and the required allocation size is returned in temp_storage_bytes.

Snippet: The code snippet below illustrates the batched sorting of three segments (with one zero-length segment) of int keys.

: #include <cub/cub.cuh> // or equivalently <cub/device/device_segmented_radix_sort.cuh>

// Declare, allocate, and initialize device-accessible pointers for sorting data

int num_items; // e.g., 7

int num_segments; // e.g., 3

int *d_offsets; // e.g., [0, 3, 3, 7]

int *d_key_buf; // e.g., [8, 6, 7, 5, 3, 0, 9]

int *d_key_alt_buf; // e.g., [-, -, -, -, -, -, -]

...

// Create a DoubleBuffer to wrap the pair of device pointers

cub::DoubleBuffer<int> d_keys(d_key_buf, d_key_alt_buf);

// Determine temporary device storage requirements

void *d_temp_storage = NULL;

size_t temp_storage_bytes = 0;

cub::DeviceSegmentedRadixSort::SortKeysDescending(d_temp_storage, temp_storage_bytes, d_keys,

num_items, num_segments, d_offsets, d_offsets + 1);

// Allocate temporary storage

cudaMalloc(&d_temp_storage, temp_storage_bytes);

// Run sorting operation

cub::DeviceSegmentedRadixSort::SortKeysDescending(d_temp_storage, temp_storage_bytes, d_keys,

num_items, num_segments, d_offsets, d_offsets + 1);

// d_keys.Current() <-- [8, 7, 6, 9, 5, 3, 0]

Template Parameters

KeyT	[inferred] Key type
BeginOffsetIteratorT	[inferred] Random-access input iterator type for reading segment beginning offsets (may be a simple pointer type)
EndOffsetIteratorT	[inferred] Random-access input iterator type for reading segment ending offsets (may be a simple pointer type)

Parameters

[in]	d_temp_storage	Device-accessible allocation of temporary storage. When NULL, the required allocation size is written to `temp_storage_bytes` and no work is done.
[in,out]	temp_storage_bytes	Reference to size in bytes of `d_temp_storage` allocation
[in,out]	d_keys	Reference to the double-buffer of keys whose "current" device-accessible buffer contains the unsorted input keys and, upon return, is updated to point to the sorted output keys
[in]	num_items	The total number of items to sort (across all segments)
[in]	num_segments	The number of segments that comprise the sorting data
[in]	d_begin_offsets	Random-access input iterator to the sequence of beginning offsets of length `num_segments`, such that `d_begin_offsets[i]` is the first element of the i^th data segment in `d_keys_` and `d_values_`
[in]	d_end_offsets	Random-access input iterator to the sequence of ending offsets of length `num_segments`, such that `d_end_offsets[i]-1` is the last element of the i^th data segment in `d_keys_` and `d_values_`. If `d_end_offsets[i]-1` <= `d_begin_offsets[i]`, the i^th is considered empty.
[in]	begin_bit	[optional] The least-significant bit index (inclusive) needed for key comparison
[in]	end_bit	[optional] The most-significant bit index (exclusive) needed for key comparison (e.g., sizeof(unsigned int) * 8)
[in]	stream	[optional] CUDA stream to launch kernels within. Default is stream₀.
[in]	debug_synchronous	[optional] 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 `false`.

The documentation for this struct was generated from the following file:

device_segmented_radix_sort.cuh

Detailed description

Static Public Methods

Member Function Documentation