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/*
* Copyright 2008-2013 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file thrust/iterator/discard_iterator.h
* \brief An iterator which "discards" (ignores) values assigned to it upon dereference
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/iterator/detail/discard_iterator_base.h>
#include <thrust/iterator/iterator_facade.h>
THRUST_DISABLE_MSVC_POSSIBLE_LOSS_OF_DATA_WARNING_BEGIN
THRUST_NAMESPACE_BEGIN
/*! \addtogroup iterators
* \{
*/
/*! \addtogroup fancyiterator Fancy Iterators
* \ingroup iterators
* \{
*/
/*! \p discard_iterator is an iterator which represents a special kind of pointer that
* ignores values written to it upon dereference. This iterator is useful for ignoring
* the output of certain algorithms without wasting memory capacity or bandwidth.
* \p discard_iterator may also be used to count the size of an algorithm's output which
* may not be known a priori.
*
* The following code snippet demonstrates how to use \p discard_iterator to ignore
* ignore one of the output ranges of reduce_by_key
*
* \code
* #include <thrust/iterator/discard_iterator.h>
* #include <thrust/reduce.h>
* #include <thrust/device_vector.h>
*
* int main()
* {
* thrust::device_vector<int> keys(7), values(7);
*
* keys[0] = 1;
* keys[1] = 3;
* keys[2] = 3;
* keys[3] = 3;
* keys[4] = 2;
* keys[5] = 2;
* keys[6] = 1;
*
* values[0] = 9;
* values[1] = 8;
* values[2] = 7;
* values[3] = 6;
* values[4] = 5;
* values[5] = 4;
* values[6] = 3;
*
* thrust::device_vector<int> result(4);
*
* // we are only interested in the reduced values
* // use discard_iterator to ignore the output keys
* thrust::reduce_by_key(keys.begin(), keys.end(),
* values.begin(),
* thrust::make_discard_iterator(),
* result.begin());
*
* // result is now [9, 21, 9, 3]
*
* return 0;
* }
* \endcode
*
* \see make_discard_iterator
*/
template<typename System = use_default>
class discard_iterator
: public detail::discard_iterator_base<System>::type
{
/*! \cond
*/
friend class thrust::iterator_core_access;
typedef typename detail::discard_iterator_base<System>::type super_t;
typedef typename detail::discard_iterator_base<System>::incrementable incrementable;
typedef typename detail::discard_iterator_base<System>::base_iterator base_iterator;
public:
typedef typename super_t::reference reference;
typedef typename super_t::value_type value_type;
/*! \endcond
*/
/*! Copy constructor copies from a source discard_iterator.
*
* \p rhs The discard_iterator to copy.
*/
__host__ __device__
discard_iterator(discard_iterator const &rhs)
: super_t(rhs.base()) {}
#if THRUST_CPP_DIALECT >= 2011
discard_iterator & operator=(const discard_iterator &) = default;
#endif
/*! This constructor receives an optional index specifying the position of this
* \p discard_iterator in a range.
*
* \p i The index of this \p discard_iterator in a range. Defaults to the
* value returned by \c Incrementable's null constructor. For example,
* when <tt>Incrementable == int</tt>, \c 0.
*/
__host__ __device__
discard_iterator(incrementable const &i = incrementable())
: super_t(base_iterator(i)) {}
/*! \cond
*/
private: // Core iterator interface
__host__ __device__
reference dereference() const
{
return m_element;
}
mutable value_type m_element;
/*! \endcond
*/
}; // end constant_iterator
/*! \p make_discard_iterator creates a \p discard_iterator from an optional index parameter.
*
* \param i The index of the returned \p discard_iterator within a range.
* In the default case, the value of this parameter is \c 0.
*
* \return A new \p discard_iterator with index as given by \p i.
*
* \see constant_iterator
*/
inline __host__ __device__
discard_iterator<> make_discard_iterator(discard_iterator<>::difference_type i = discard_iterator<>::difference_type(0))
{
return discard_iterator<>(i);
} // end make_discard_iterator()
/*! \} // end fancyiterators
*/
/*! \} // end iterators
*/
THRUST_NAMESPACE_END
THRUST_DISABLE_MSVC_POSSIBLE_LOSS_OF_DATA_WARNING_END
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