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 intooutput
.- Overview
Returns the required size of
temporary_storage
instorage_size
iftemporary_storage
in a null pointer.Range specified by
input
must have at leastsize
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 haveconst &
, 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#
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