Unique

Unique#

unique#

template<class Config = default_config, class InputIterator, class OutputIterator, class UniqueCountOutputIterator, class EqualityOp = ::rocprim::equal_to<typename std::iterator_traits<InputIterator>::value_type>> inline hipError_t rocprim::unique(void *temporary_storage, size_t &storage_size, InputIterator input, OutputIterator output, UniqueCountOutputIterator unique_count_output, const size_t size, EqualityOp equality_op = EqualityOp(), const hipStream_t stream = 0, const bool debug_synchronous = false)#

Device-level parallel unique primitive.

From given input range unique primitive eliminates all but the first element from every consecutive group of equivalent elements and copies them into output.

Overview

Returns the required size of temporary_storage in storage_size if temporary_storage is a null pointer.
Range specified by input must have at least size elements.
Range specified by output must have at least so many elements, that all selected values can be copied into it.
Range specified by unique_count_output must have at least 1 element.
By default InputIterator::value_type’s equality operator is used to check if elements are equivalent.

Example

In this example a device-level unique operation is performed on an array of integer values.

#include <rocprim/rocprim.hpp>

// Prepare input and output (declare pointers, allocate device memory etc.)
size_t input_size;     // e.g., 8
int * input;           // e.g., [1, 4, 2, 4, 4, 7, 7, 7]
int * output;          // empty array of 8 elements
size_t * output_count; // empty array of 1 element

size_t temporary_storage_size_bytes;
void * temporary_storage_ptr = nullptr;
// Get required size of the temporary storage
rocprim::unique(
    temporary_storage_ptr, temporary_storage_size_bytes,
    input, output, output_count,
    input_size
);

// allocate temporary storage
hipMalloc(&temporary_storage_ptr, temporary_storage_size_bytes);

// perform unique operation
rocprim::unique(
    temporary_storage_ptr, temporary_storage_size_bytes,
    input, output, output_count,
    input_size
);
// output: [1, 4, 2, 4, 7]
// output_count: 5

Template Parameters:

InputIterator – - random-access iterator type of the input range. It can be a simple pointer type.
OutputIterator – - random-access iterator type of the output range. It can be a simple pointer type.
UniqueCountOutputIterator – - random-access iterator type of the unique_count_output value used to return number of unique values. It can be a simple pointer type.
EqualityOp – - type of an binary operator used to compare values for equality.

Parameters:

temporary_storage – [in] - pointer to a device-accessible temporary storage. When a null pointer is passed, the required allocation size (in bytes) is written to storage_size and function returns without performing the unique operation.
storage_size – [inout] - reference to a size (in bytes) of temporary_storage.
input – [in] - iterator to the first element in the range to select values from.
output – [out] - iterator to the first element in the output range.
unique_count_output – [out] - iterator to the total number of selected values (length of output).
size – [in] - number of element in the input range.
equality_op – [in] - [optional] binary function object used to compare input values for equality. The signature of the function should be equivalent to the following: bool equal_to(const T &a, const T &b);. The signature does not need to have const &, but function object must not modify the object passed to it.
stream – [in] - [optional] HIP stream object. The default is 0 (default stream).
debug_synchronous – [in] - [optional] If true, synchronization after every kernel launch is forced in order to check for errors. The default value is false.

unique_by_key#

template<typename Config = default_config, typename KeyIterator, typename ValueIterator, typename OutputKeyIterator, typename OutputValueIterator, typename UniqueCountOutputIterator, typename EqualityOp = ::rocprim::equal_to<typename std::iterator_traits<KeyIterator>::value_type>> inline hipError_t rocprim::unique_by_key(void *temporary_storage, size_t &storage_size, const KeyIterator keys_input, const ValueIterator values_input, const OutputKeyIterator keys_output, const OutputValueIterator values_output, const UniqueCountOutputIterator unique_count_output, const size_t size, const EqualityOp equality_op = EqualityOp(), const hipStream_t stream = 0, const bool debug_synchronous = false)#

Device-level parallel unique by key primitive.

From given input range unique primitive eliminates all but the first element from every consecutive group of equivalent elements and copies them and their corresponding keys into output.