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#ifndef ROCPRIM_DEVICE_DEVICE_SELECT_HPP_
#define ROCPRIM_DEVICE_DEVICE_SELECT_HPP_

#include <type_traits>
#include <iterator>

#include "../config.hpp"
#include "../detail/various.hpp"
#include "../detail/binary_op_wrappers.hpp"

#include "../iterator/transform_iterator.hpp"

#include "device_partition.hpp"

BEGIN_ROCPRIM_NAMESPACE

/// \addtogroup devicemodule
/// @{

namespace detail
{

} // end detail namespace

/// \brief Parallel select primitive for device level using range of flags.
///
/// Performs a device-wide selection based on input \p flags. If a value from \p input
/// should be selected and copied into \p output range the corresponding item from
/// \p flags range should be set to such value that can be implicitly converted to
/// \p true (\p bool type).
///
/// \par Overview
/// * Returns the required size of \p temporary_storage in \p storage_size
/// if \p temporary_storage in a null pointer.
/// * Ranges specified by \p input and \p flags must have at least \p size elements.
/// * Range specified by \p output must have at least so many elements, that all positively
/// flagged values can be copied into it.
/// * Range specified by \p selected_count_output must have at least 1 element.
/// * Values of \p flag range should be implicitly convertible to `bool` type.
///
/// \tparam Config - [optional] configuration of the primitive. It can be \p select_config or
/// a custom class with the same members.
/// \tparam InputIterator - random-access iterator type of the input range. It can be
/// a simple pointer type.
/// \tparam FlagIterator - random-access iterator type of the flag range. It can be
/// a simple pointer type.
/// \tparam OutputIterator - random-access iterator type of the output range. It can be
/// a simple pointer type.
/// \tparam SelectedCountOutputIterator - random-access iterator type of the selected_count_output
/// value. It can be a simple pointer type.
///
/// \param [in] temporary_storage - pointer to a device-accessible temporary storage. When
/// a null pointer is passed, the required allocation size (in bytes) is written to
/// \p storage_size and function returns without performing the select operation.
/// \param [in,out] storage_size - reference to a size (in bytes) of \p temporary_storage.
/// \param [in] input - iterator to the first element in the range to select values from.
/// \param [in] flags - iterator to the selection flag corresponding to the first element from \p input range.
/// \param [out] output - iterator to the first element in the output range.
/// \param [out] selected_count_output - iterator to the total number of selected values (length of \p output).
/// \param [in] size - number of element in the input range.
/// \param [in] stream - [optional] HIP stream object. The default is \p 0 (default stream).
/// \param [in] debug_synchronous - [optional] If true, synchronization after every kernel
/// launch is forced in order to check for errors. The default value is \p false.
///
/// \par Example
/// \parblock
/// In this example a device-level select operation is performed on an array of
/// integer values with array of <tt>char</tt>s used as flags.
///
/// \code{.cpp}
/// #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, 2, 3, 4, 5, 6, 7, 8]
/// char * flags;          // e.g., [0, 1, 1, 0, 0, 1, 0, 1]
/// 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::select(
///     temporary_storage_ptr, temporary_storage_size_bytes,
///     input, flags,
///     output, output_count,
///     input_size
/// );
///
/// // allocate temporary storage
/// hipMalloc(&temporary_storage_ptr, temporary_storage_size_bytes);
///
/// // perform selection
/// rocprim::select(
///     temporary_storage_ptr, temporary_storage_size_bytes,
///     input, flags,
///     output, output_count,
///     input_size
/// );
/// // output: [2, 3, 6, 8]
/// // output_count: 4
/// \endcode
/// \endparblock
template<
    class Config = default_config,
    class InputIterator,
    class FlagIterator,
    class OutputIterator,
    class SelectedCountOutputIterator
>
inline
hipError_t select(void * temporary_storage,
                  size_t& storage_size,
                  InputIterator input,
                  FlagIterator flags,
                  OutputIterator output,
                  SelectedCountOutputIterator selected_count_output,
                  const size_t size,
                  const hipStream_t stream = 0,
                  const bool debug_synchronous = false)
{
    // Dummy unary predicate
    using unary_predicate_type = ::rocprim::empty_type;
    // Dummy inequality operation
    using inequality_op_type = ::rocprim::empty_type;
    using offset_type = unsigned int;
    rocprim::empty_type* const no_values = nullptr; // key only

    return detail::partition_impl<detail::select_method::flag, true, Config, offset_type>(
        temporary_storage, storage_size, input, no_values, flags, output, no_values, selected_count_output,
        size, inequality_op_type(), stream, debug_synchronous, unary_predicate_type()
    );
}

/// \brief Parallel select primitive for device level using selection operator.
///
/// Performs a device-wide selection using selection operator. If a value \p x from \p input
/// should be selected and copied into \p output range, then <tt>predicate(x)</tt> has to
/// return \p true.
///
/// \par Overview
/// * Returns the required size of \p temporary_storage in \p storage_size
/// if \p temporary_storage in a null pointer.
/// * Range specified by \p input must have at least \p size elements.
/// * Range specified by \p output must have at least so many elements, that all selected
/// values can be copied into it.
/// * Range specified by \p selected_count_output must have at least 1 element.
///
/// \tparam Config - [optional] configuration of the primitive. It can be \p select_config or
/// a custom class with the same members.
/// \tparam InputIterator - random-access iterator type of the input range. It can be
/// a simple pointer type.
/// \tparam OutputIterator - random-access iterator type of the output range. It can be
/// a simple pointer type.
/// \tparam SelectedCountOutputIterator - random-access iterator type of the selected_count_output
/// value. It can be a simple pointer type.
/// \tparam UnaryPredicate - type of a unary selection predicate.
///
/// \param [in] temporary_storage - pointer to a device-accessible temporary storage. When
/// a null pointer is passed, the required allocation size (in bytes) is written to
/// \p storage_size and function returns without performing the select operation.
/// \param [in,out] storage_size - reference to a size (in bytes) of \p temporary_storage.
/// \param [in] input - iterator to the first element in the range to select values from.
/// \param [out] output - iterator to the first element in the output range.
/// \param [out] selected_count_output - iterator to the total number of selected values (length of \p output).
/// \param [in] size - number of element in the input range.
/// \param [in] predicate - unary function object that will be used for selecting values.
/// The signature of the function should be equivalent to the following:
/// <tt>bool f(const T &a);</tt>. The signature does not need to have
/// <tt>const &</tt>, but function object must not modify the object passed to it.
/// \param [in] stream - [optional] HIP stream object. The default is \p 0 (default stream).
/// \param [in] debug_synchronous - [optional] If true, synchronization after every kernel
/// launch is forced in order to check for errors. The default value is \p false.
///
/// \par Example
/// \parblock
/// In this example a device-level select operation is performed on an array of
/// integer values, only even values are selected.
///
/// \code{.cpp}
/// #include <rocprim/rocprim.hpp>
///
/// auto predicate =
///     [] __device__ (int a) -> bool
///     {
///         return (a%2) == 0;
///     };
///
/// // Prepare input and output (declare pointers, allocate device memory etc.)
/// size_t input_size;     // e.g., 8
/// int * input;           // e.g., [1, 2, 3, 4, 5, 6, 7, 8]
/// 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::select(
///     temporary_storage_ptr, temporary_storage_size_bytes,
///     input, output, output_count,
///     predicate, input_size
/// );
///
/// // allocate temporary storage
/// hipMalloc(&temporary_storage_ptr, temporary_storage_size_bytes);
///
/// // perform selection
/// rocprim::select(
///     temporary_storage_ptr, temporary_storage_size_bytes,
///     input, output, output_count,
///     predicate, input_size
/// );
/// // output: [2, 4, 6, 8]
/// // output_count: 4
/// \endcode
/// \endparblock
template<
    class Config = default_config,
    class InputIterator,
    class OutputIterator,
    class SelectedCountOutputIterator,
    class UnaryPredicate
>
inline
hipError_t select(void * temporary_storage,
                  size_t& storage_size,
                  InputIterator input,
                  OutputIterator output,
                  SelectedCountOutputIterator selected_count_output,
                  const size_t size,
                  UnaryPredicate predicate,
                  const hipStream_t stream = 0,
                  const bool debug_synchronous = false)
{
    // Dummy flag type
    using flag_type = ::rocprim::empty_type;
    using offset_type = unsigned int;
    flag_type * flags = nullptr;
    // Dummy inequality operation
    using inequality_op_type = ::rocprim::empty_type;
    rocprim::empty_type* const no_values = nullptr; // key only

    return detail::partition_impl<detail::select_method::predicate, true, Config, offset_type>(
        temporary_storage, storage_size, input, no_values, flags, output, no_values, selected_count_output,
        size, inequality_op_type(), stream, debug_synchronous, predicate
    );
}

/// \brief Device-level parallel unique primitive.
///
/// From given \p input range unique primitive eliminates all but the first element from every
/// consecutive group of equivalent elements and copies them into \p output.
///
/// \par Overview
/// * Returns the required size of \p temporary_storage in \p storage_size
/// if \p temporary_storage is a null pointer.
/// * Range specified by \p input must have at least \p size elements.
/// * Range specified by \p output must have at least so many elements, that all selected
/// values can be copied into it.
/// * Range specified by \p unique_count_output must have at least 1 element.
/// * By default <tt>InputIterator::value_type</tt>'s equality operator is used to check
/// if elements are equivalent.
///
/// \tparam InputIterator - random-access iterator type of the input range. It can be
/// a simple pointer type.
/// \tparam OutputIterator - random-access iterator type of the output range. It can be
/// a simple pointer type.
/// \tparam 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.
/// \tparam EqualityOp - type of an binary operator used to compare values for equality.
///
/// \param [in] temporary_storage - pointer to a device-accessible temporary storage. When
/// a null pointer is passed, the required allocation size (in bytes) is written to
/// \p storage_size and function returns without performing the unique operation.
/// \param [in,out] storage_size - reference to a size (in bytes) of \p temporary_storage.
/// \param [in] input - iterator to the first element in the range to select values from.
/// \param [out] output - iterator to the first element in the output range.
/// \param [out] unique_count_output - iterator to the total number of selected values (length of \p output).
/// \param [in] size - number of element in the input range.
/// \param [in] equality_op - [optional] binary function object used to compare input values for equality.
/// The signature of the function should be equivalent to the following:
/// <tt>bool equal_to(const T &a, const T &b);</tt>. The signature does not need to have
/// <tt>const &</tt>, but function object must not modify the object passed to it.
/// \param [in] stream - [optional] HIP stream object. The default is \p 0 (default stream).
/// \param [in] debug_synchronous - [optional] If true, synchronization after every kernel
/// launch is forced in order to check for errors. The default value is \p false.
///
/// \par Example
/// \parblock
/// In this example a device-level unique operation is performed on an array of integer values.
///
/// \code{.cpp}
/// #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
/// \endcode
/// \endparblock
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 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)
{
    // Dummy unary predicate
    using unary_predicate_type = ::rocprim::empty_type;
    using offset_type = unsigned int;
    // Dummy flag type
    using flag_type = ::rocprim::empty_type;
    const flag_type * flags = nullptr;
    rocprim::empty_type* const no_values = nullptr; // key only

    // Convert equality operator to inequality operator
    auto inequality_op = detail::inequality_wrapper<EqualityOp>(equality_op);

    return detail::partition_impl<detail::select_method::unique, true, Config, offset_type>(
        temporary_storage, storage_size, input, no_values, flags, output, no_values, unique_count_output,
        size, inequality_op, stream, debug_synchronous, unary_predicate_type()
    );
}

/// \brief Device-level parallel unique by key primitive.
///
/// From given \p 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
/// \p output.
///
/// \par Overview
/// * Returns the required size of \p temporary_storage in \p storage_size
/// if \p temporary_storage is a null pointer.
/// * Ranges specified by \p keys_input and value_input must have at least \p size elements each.
/// * Ranges specified by \p keys_output and values_output each must have at least so many elements,
/// that all selected values can be copied into them.
/// * Range specified by \p unique_count_output must have at least 1 element.
/// * By default <tt>InputIterator::value_type</tt>'s equality operator is used to check
/// if elements are equivalent.
///
/// \tparam KeyIterator - random-access iterator type of the input key range. It can be
/// a simple pointer type.
/// \tparam ValueIterator - random-access iterator type of the input value range. It can be
/// a simple pointer type.
/// \tparam OutputKeyIterator - random-access iterator type of the output key range. It can be
/// a simple pointer type.
/// \tparam OutputValueIterator - random-access iterator type of the output value range. It can be
/// a simple pointer type.
/// \tparam UniqueCountOutputIterator - random-access iterator type of the unique_count_output
/// value used to return number of unique keys and values. It can be a simple pointer type.
/// \tparam EqualityOp - type of an binary operator used to compare keys for equality.
///
/// \param [in] temporary_storage - pointer to a device-accessible temporary storage. When
/// a null pointer is passed, the required allocation size (in bytes) is written to
/// \p storage_size and function returns without performing the unique operation.
/// \param [in,out] storage_size - reference to a size (in bytes) of \p temporary_storage.
/// \param [in] keys_input - iterator to the first element in the range to select keys from.
/// \param [in] values_input - iterator to the first element in the range of values corresponding to keys
/// \param [out] keys_output - iterator to the first element in the output key range.
/// \param [out] values_output - iterator to the first element in the output value range.
/// \param [out] unique_count_output - iterator to the total number of selected values (length of \p output).
/// \param [in] size - number of element in the input range.
/// \param [in] equality_op - [optional] binary function object used to compare input values for equality.
/// The signature of the function should be equivalent to the following:
/// <tt>bool equal_to(const T &a, const T &b);</tt>. The signature does not need to have
/// <tt>const &</tt>, but function object must not modify the object passed to it.
/// \param [in] stream - [optional] HIP stream object. The default is \p 0 (default stream).
/// \param [in] debug_synchronous - [optional] If true, synchronization after every kernel
/// launch is forced in order to check for errors. The default value is \p false.
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 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)
{
    using offset_type = unsigned int;
    // Dummy flag
    ::rocprim::empty_type* const no_flags = nullptr;
    // Dummy predicate
    const auto no_predicate = ::rocprim::empty_type{};

    // Convert equality operator to inequality operator
    const auto inequality_op = detail::inequality_wrapper<EqualityOp>(equality_op);

    return detail::partition_impl<detail::select_method::unique, true, Config, offset_type>(
        temporary_storage,
        storage_size,
        keys_input,
        values_input,
        no_flags,
        keys_output,
        values_output,
        unique_count_output,
        size,
        inequality_op,
        stream,
        debug_synchronous,
        no_predicate);
}

/// @}
// end of group devicemodule

END_ROCPRIM_NAMESPACE

#endif // ROCPRIM_DEVICE_DEVICE_SELECT_HPP_
