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   * Copyright (c) 2011, Duane Merrill.  All rights reserved.
   * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
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  /**
   * \file
   * Random-access iterator types
   */
  
  #pragma once
  
  #include <iterator>
  #include <iostream>
  
  #include "../thread/thread_load.cuh"
  #include "../thread/thread_store.cuh"
  #include "../util_device.cuh"
  #include "../util_namespace.cuh"
  
  #if (THRUST_VERSION >= 100700)
      // This iterator is compatible with Thrust API 1.7 and newer
      #include <thrust/iterator/iterator_facade.h>
      #include <thrust/iterator/iterator_traits.h>
  #endif // THRUST_VERSION
  
  
  /// Optional outer namespace(s)
  CUB_NS_PREFIX
  
  /// CUB namespace
  namespace cub {
  
  
  
  /**
   * \addtogroup UtilIterator
   * @{
   */
  
  
  /**
   * \brief A random-access input wrapper for dereferencing array values using a PTX cache load modifier.
   *
   * \par Overview
   * - CacheModifiedInputIteratorTis a random-access input iterator that wraps a native
   *   device pointer of type <tt>ValueType*</tt>. \p ValueType references are
   *   made by reading \p ValueType values through loads modified by \p MODIFIER.
   * - Can be used to load any data type from memory using PTX cache load modifiers (e.g., "LOAD_LDG",
   *   "LOAD_CG", "LOAD_CA", "LOAD_CS", "LOAD_CV", etc.).
   * - Can be constructed, manipulated, and exchanged within and between host and device
   *   functions, but can only be dereferenced within device functions.
   * - Compatible with Thrust API v1.7 or newer.
   *
   * \par Snippet
   * The code snippet below illustrates the use of \p CacheModifiedInputIteratorTto
   * dereference a device array of double using the "ldg" PTX load modifier
   * (i.e., load values through texture cache).
   * \par
   * \code
   * #include <cub/cub.cuh>   // or equivalently <cub/iterator/cache_modified_input_iterator.cuh>
   *
   * // Declare, allocate, and initialize a device array
   * double *d_in;            // e.g., [8.0, 6.0, 7.0, 5.0, 3.0, 0.0, 9.0]
   *
   * // Create an iterator wrapper
   * cub::CacheModifiedInputIterator<cub::LOAD_LDG, double> itr(d_in);
   *
   * // Within device code:
   * printf("%f
  ", itr[0]);  // 8.0
   * printf("%f
  ", itr[1]);  // 6.0
   * printf("%f
  ", itr[6]);  // 9.0
   *
   * \endcode
   *
   * \tparam CacheLoadModifier    The cub::CacheLoadModifier to use when accessing data
   * \tparam ValueType            The value type of this iterator
   * \tparam OffsetT              The difference type of this iterator (Default: \p ptrdiff_t)
   */
  template <
      CacheLoadModifier   MODIFIER,
      typename            ValueType,
      typename            OffsetT = ptrdiff_t>
  class CacheModifiedInputIterator
  {
  public:
  
      // Required iterator traits
      typedef CacheModifiedInputIterator          self_type;              ///< My own type
      typedef OffsetT                             difference_type;        ///< Type to express the result of subtracting one iterator from another
      typedef ValueType                           value_type;             ///< The type of the element the iterator can point to
      typedef ValueType*                          pointer;                ///< The type of a pointer to an element the iterator can point to
      typedef ValueType                           reference;              ///< The type of a reference to an element the iterator can point to
  
  #if (THRUST_VERSION >= 100700)
      // Use Thrust's iterator categories so we can use these iterators in Thrust 1.7 (or newer) methods
      typedef typename thrust::detail::iterator_facade_category<
          thrust::device_system_tag,
          thrust::random_access_traversal_tag,
          value_type,
          reference
        >::type iterator_category;                                        ///< The iterator category
  #else
      typedef std::random_access_iterator_tag     iterator_category;      ///< The iterator category
  #endif  // THRUST_VERSION
  
  
  public:
  
      /// Wrapped native pointer
      ValueType* ptr;
  
      /// Constructor
      template <typename QualifiedValueType>
      __host__ __device__ __forceinline__ CacheModifiedInputIterator(
          QualifiedValueType* ptr)     ///< Native pointer to wrap
      :
          ptr(const_cast<typename RemoveQualifiers<QualifiedValueType>::Type *>(ptr))
      {}
  
      /// Postfix increment
      __host__ __device__ __forceinline__ self_type operator++(int)
      {
          self_type retval = *this;
          ptr++;
          return retval;
      }
  
      /// Prefix increment
      __host__ __device__ __forceinline__ self_type operator++()
      {
          ptr++;
          return *this;
      }
  
      /// Indirection
      __device__ __forceinline__ reference operator*() const
      {
          return ThreadLoad<MODIFIER>(ptr);
      }
  
      /// Addition
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type operator+(Distance n) const
      {
          self_type retval(ptr + n);
          return retval;
      }
  
      /// Addition assignment
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type& operator+=(Distance n)
      {
          ptr += n;
          return *this;
      }
  
      /// Subtraction
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type operator-(Distance n) const
      {
          self_type retval(ptr - n);
          return retval;
      }
  
      /// Subtraction assignment
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type& operator-=(Distance n)
      {
          ptr -= n;
          return *this;
      }
  
      /// Distance
      __host__ __device__ __forceinline__ difference_type operator-(self_type other) const
      {
          return ptr - other.ptr;
      }
  
      /// Array subscript
      template <typename Distance>
      __device__ __forceinline__ reference operator[](Distance n) const
      {
          return ThreadLoad<MODIFIER>(ptr + n);
      }
  
      /// Structure dereference
      __device__ __forceinline__ pointer operator->()
      {
          return &ThreadLoad<MODIFIER>(ptr);
      }
  
      /// Equal to
      __host__ __device__ __forceinline__ bool operator==(const self_type& rhs)
      {
          return (ptr == rhs.ptr);
      }
  
      /// Not equal to
      __host__ __device__ __forceinline__ bool operator!=(const self_type& rhs)
      {
          return (ptr != rhs.ptr);
      }
  
      /// ostream operator
      friend std::ostream& operator<<(std::ostream& os, const self_type& /*itr*/)
      {
          return os;
      }
  };
  
  
  
  /** @} */       // end group UtilIterator
  
  }               // CUB namespace
  CUB_NS_POSTFIX  // Optional outer namespace(s)