Intrepid2_FunctorIterator.hpp

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#ifndef Intrepid2_FunctorIterator_h
#define Intrepid2_FunctorIterator_h

namespace Intrepid2
{
  template<typename FunctorType, typename ScalarType, int rank>
  class functor_returns_ref{};

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,0>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()());
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,1>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,2>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,3>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,4>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0,0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,5>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0,0,0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,6>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0,0,0,0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<typename FunctorType, typename ScalarType>
  class functor_returns_ref<FunctorType,ScalarType,7>
  {
    using return_type        = decltype(std::declval<FunctorType>().operator()(0,0,0,0,0,0,0));
    using return_type_no_ref = typename std::remove_reference<return_type>::type;
  public:
    static constexpr bool value = !std::is_same<return_type, return_type_no_ref>::value;
  };

  template<class FunctorType, typename ScalarType, int rank>
  class FunctorIterator
  {
    const FunctorType &functor_;
    Kokkos::Array<int,7> dims_; // 7 is the maximum rank of a Kokkos view
    Kokkos::Array<int,7> index_;
  public:
    KOKKOS_INLINE_FUNCTION
    FunctorIterator(const FunctorType &functor)
    :
    functor_(functor)
    {
      for (int d=0; d<rank; d++)
      {
        dims_[d] = functor.extent_int(d);
        index_[d] = 0;
      }
      for (int d=rank; d<7; d++)
      {
        dims_[d] = 1;
        index_[d] = 0;
      }
    }
    
    using return_type = typename std::conditional< functor_returns_ref<FunctorType, ScalarType, rank>::value, const ScalarType &, const ScalarType>::type;
    
    template< bool B, class T = return_type >
    using enable_if_t = typename std::enable_if<B,T>::type;
    
    template<int M = rank>
    enable_if_t<M==0>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_();
    }
    
    template<int M = rank>
    enable_if_t<M==1>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0]);
    }
    
    template<int M = rank>
    enable_if_t<M==2>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1]);
    }
    
    template<int M = rank>
    enable_if_t<M==3>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1], index_[2]);
    }
    
    template<int M = rank>
    enable_if_t<M==4>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1], index_[2], index_[3]);
    }
    
    template<int M = rank>
    enable_if_t<M==5>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1], index_[2], index_[3], index_[4]);
    }
    
    
    template<int M = rank>
    enable_if_t<M==6>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1], index_[2], index_[3], index_[4], index_[5]);
    }
    
    template<int M = rank>
    enable_if_t<M==7>
    KOKKOS_INLINE_FUNCTION
    get() const
    {
      return functor_(index_[0], index_[1], index_[2], index_[3], index_[4], index_[5], index_[6]);
    }
    
    KOKKOS_INLINE_FUNCTION
    int nextIncrementRank()
    {
      for (int r=rank-1; r>=0; r--)
      {
        if (index_[r]+1 < dims_[r]) // can increment without going out of bounds in this dimension
        {
          return r;
        }
      }
      // next increment will take us out of bounds
      return -1;
    }
    
    KOKKOS_INLINE_FUNCTION
    int increment()
    {
      for (int r=rank-1; r>=0; r--)
      {
        if (index_[r]+1 < dims_[r]) // can increment without going out of bounds in this dimension
        {
          index_[r]++;
          // we've completed the increment
          return r;
        }
        else
        {
          // next rank should be incremented -- this one should reset to 0
          index_[r] = 0;
        }
      }
      // if we get here, we have run through all ranks, setting them to 0 -- we've cycled around
      // and in that sense have not completed the increment
      return -1;
    }
    
    KOKKOS_INLINE_FUNCTION
    bool decrement()
    {
      for (int r=rank-1; r>=0; r--)
      {
        if (index_[r]-1 >= 0) // can decrement without going out of bounds in this dimension
        {
          index_[r]--;
          return true; // we've completed the decrement
        }
        else
        {
          // next rank should be decremented -- this one should cycle round to dim_[r]-1
          index_[r] = dims_[r]-1;
        }
      }
      // if we get here, we've gone past 0 in every dimension, so we should return false
      // -- we have not completed the decrement in an in-bounds fashion, but have cycled round to the last value
      // to maintain a clean state, let's reset
      reset();
      return false;
    }
    
    KOKKOS_INLINE_FUNCTION
    int getEnumerationIndex()
    {
      int index_1D = 0;
      for (int d=0; d<7; d++)
      {
        if (d>0) index_1D *= dims_[d-1];
        index_1D += index_[d];
      }
      
      return index_1D;
    }
    
    KOKKOS_INLINE_FUNCTION
    void setEnumerationIndex(const int &enumerationIndex)
    {
      Kokkos::Array<int,7> location;
      int remainder = enumerationIndex;
      for (int d=6; d>=0; d--)
      {
        location[d] = remainder % dims_[d];
        remainder  /= dims_[d];
      }
      
      setLocation(location);
    }
    
    KOKKOS_INLINE_FUNCTION
    int getIndex(int dimension)
    {
      return index_[dimension];
    }
    
    KOKKOS_INLINE_FUNCTION
    int getExtent(int dimension)
    {
      return dims_[dimension];
    }
    
    KOKKOS_INLINE_FUNCTION
    void reset(unsigned from_rank_number=0)
    {
      for (unsigned d=from_rank_number; d<functor_.rank(); d++)
      {
        index_[d] = 0;
      }
    }
    
    KOKKOS_INLINE_FUNCTION
    void setLocation(const Kokkos::Array<int,7> &location)
    {
      index_ = location;
    }
    
    KOKKOS_INLINE_FUNCTION
    void setLocationInDim(const int &dim, const int &i)
    {
      index_[dim] = i;
    }
    
    KOKKOS_INLINE_FUNCTION
    Kokkos::Array<int,7> & getLocation()
    {
      return index_;
    }
  };
} // end namespace Intrepid2

#endif /* Intrepid2_FunctorIterator_h */