Search

Configuring the kernel

template<unsigned int BlockSize, unsigned int ItemsPerThread, unsigned int MaxSharedKeyBytes>
struct search_config : public rocprim::detail::search_config_params

Configuration of device-level find_end.

Template Parameters:

• BlockSize – number of threads in a block.

• ItemsPerThread – number of items processed by each thread.

• MaxSharedKeyBytes – maximum number of bytes for which a shared key is used.

search

template<class Config = default_config, class InputIterator1, class InputIterator2, class OutputIterator, class BinaryFunction = rocprim::equal_to<typename std::iterator_traits<InputIterator1>::value_type>>
inline hipError_t rocprim::search(void *temporary_storage, size_t &storage_size, InputIterator1 input, InputIterator2 keys, OutputIterator output, size_t size, size_t keys_size, BinaryFunction compare_function = BinaryFunction(), hipStream_t stream = 0, bool debug_synchronous = false)

Searches for the first occurrence of the sequence.

Searches the input for the first occurence of a sequence, according to a particular comparison function. If found, the index of the first item of the found sequence in the input is returned. Otherwise, returns the size of the input.

Overview

• The contents of the inputs are not altered by the function.

• Returns the required size of temporary_storage in storage_size if temporary_storage is a null pointer.

• Accepts custom compare_functions for search across the device.

• Streams in graph capture mode are supported

Example

In this example a device-level search is performed where input values are represented by an array of unsigned integers and the key is also an array of unsigned integers.

#include <rocprim/rocprim.hpp>

// Prepare input and output (declare pointers, allocate device memory etc.)
size_t size;           // e.g., 10
size_t key_size;       // e.g., 3
unsigned int * input;  // e.g., [ 6, 3, 5, 4, 1, 8, 2, 5, 4, 1 ]
unsigned int * key;    // e.g., [ 5, 4, 1 ]
unsigned int * output; // e.g., empty array of size 1

size_t temporary_storage_size_bytes;
void * temporary_storage_ptr = nullptr;
// Get required size of the temporary storage
rocprim::search(
    temporary_storage_ptr, temporary_storage_size_bytes,
    input, key, output, size, key_size
);

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

// perform search
rocprim::search(
    temporary_storage_ptr, temporary_storage_size_bytes,
    input, key, output, size, key_size
);
// output:   [ 2 ]

Template Parameters:

• Config – [optional] configuration of the primitive, must be default_config or search_config.

• InputIterator1 – [inferred] random-access iterator type of the input range. Must meet the requirements of a C++ InputIterator concept. It can be a simple pointer type.

• InputIterator2 – [inferred] random-access iterator type of the input range. Must meet the requirements of a C++ InputIterator concept. It can be a simple pointer type.

• OutputIterator – [inferred] random-access iterator type of the input range. Must meet the requirements of a C++ OutputIterator concept. It can be a simple pointer type.

• BinaryFunction – [inferred] Type of binary function that accepts two arguments of the type InputIterator1 and returns a value convertible to bool. Default type is rocprim::less<>.

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 search.

• storage_size – [inout] reference to a size (in bytes) of temporary_storage.

• input – [in] iterator to the input range.

• keys – [in] iterator to the key range.

• output – [out] iterator to the output range. The output is one element.

• size – [in] number of elements in the input range.

• keys_size – [in] number of elements in the key range.

• compare_function – [in] binary operation function object that will be used for comparison. The signature of the function should be equivalent to the following: bool f(const T &a, const T &b);. The signature does not need to have const &, but function object must not modify the objects passed to it. The comparator must meet the C++ named requirement BinaryPredicate. The default value is BinaryFunction().

• stream – [in] [optional] HIP stream object. Default is 0 (default stream).

• debug_synchronous – [in] [optional] If true, synchronization after every kernel launch is forced in order to check for errors. Default value is false.

Returns:

hipSuccess (0) after successful search; otherwise a HIP runtime error of type hipError_t.