exclusive_scan

Header File: Kokkos_StdAlgorithms.hpp

namespace Kokkos{
namespace Experimental{

//
// overload set A
//
template <
  class ExecutionSpace, class InputIteratorType,
  class OutputIteratorType, class ValueType>
OutputIteratorType exclusive_scan(const ExecutionSpace& exespace,                (1)
                                  InputIteratorType first,
                                  InputIteratorType last,
                                  OutputIteratorType first_dest,
                                  ValueType init_value);

template <
  class ExecutionSpace, class InputIteratorType,
  class OutputIteratorType, class ValueType>
OutputIteratorType exclusive_scan(const std::string& label,                      (2)
                                  const ExecutionSpace& exespace,
                                  InputIteratorType first,
                                  InputIteratorType last,
                                  OutputIteratorType first_dest,
                                  ValueType init_value);

template <
  class ExecutionSpace,
  class DataType1, class... Properties1,
  class DataType2, class... Properties2,
  class ValueType>
auto exclusive_scan(const ExecutionSpace& exespace,                              (3)
                    const ::Kokkos::View<DataType1, Properties1...>& view_from,
                    const ::Kokkos::View<DataType2, Properties2...>& view_dest,
                    ValueType init_value);

template <
  class ExecutionSpace,
  class DataType1, class... Properties1,
  class DataType2, class... Properties2,
  class ValueType>
auto exclusive_scan(const std::string& label, const ExecutionSpace& exespace,    (4)
                    const ::Kokkos::View<DataType1, Properties1...>& view_from,
                    const ::Kokkos::View<DataType2, Properties2...>& view_dest,
                    ValueType init_value);

//
// overload set B
//
template <
 class ExecutionSpace, class InputIteratorType,
 class OutputIteratorType, class ValueType, class BinaryOpType
 >
OutputIteratorType exclusive_scan(const ExecutionSpace& exespace,                (5)
                                  InputIteratorType first_from,
                                  InputIteratorType last_from,
                                  OutputIteratorType first_dest,
                                  ValueType init_value, BinaryOpType bin_op);


template <
  class ExecutionSpace, class InputIteratorType,
  class OutputIteratorType, class ValueType, class BinaryOpType
  >
OutputIteratorType exclusive_scan(const std::string& label,                      (6)
                                  const ExecutionSpace& exespace,
                                  InputIteratorType first_from,
                                  InputIteratorType last_from,
                                  OutputIteratorType first_dest,
                                  ValueType init_value, BinaryOpType bin_op);

template <
  class ExecutionSpace, class DataType1, class... Properties1,
  class DataType2, class... Properties2, class ValueType,
  class BinaryOpType>
auto exclusive_scan(const ExecutionSpace& exespace,                              (7)
                    const ::Kokkos::View<DataType1, Properties1...>& view_from,
                    const ::Kokkos::View<DataType2, Properties2...>& view_dest,
                    ValueType init_value, BinaryOpType bin_op);

template <
  class ExecutionSpace, class DataType1, class... Properties1,
  class DataType2, class... Properties2, class ValueType,
  class BinaryOpType>
auto exclusive_scan(const std::string& label, const ExecutionSpace& exespace,    (8)
                    const ::Kokkos::View<DataType1, Properties1...>& view_from,
                    const ::Kokkos::View<DataType2, Properties2...>& view_dest,
                    ValueType init_value, BinaryOpType bin_op);

} //end namespace Experimental
} //end namespace Kokkos

Description

• 1,2,3,4: computes an exclusive prefix sum for the range [first_from, last_from) (1,2) or view_from (3,4), using init as the initial value, and writes the results to the range beginning at first_dest (1,2) or to view_dest (3,4).

• 5,6,7,8: computes an exclusive prefix scan using the binary functor bin_op to combine two elements for the range [first_from, last_from) (5,6) or view_from (7,8), using init as the initial value, and writes the results to the range beginning at first_dest (5,6) or to view_dest (7,8).

Exclusive means that the i-th input element is not included in the i-th sum.

Parameters and Requirements

• exespace:

  • execution space instance

• label:

  • used to name the implementation kernels for debugging purposes

  • for 1,2 the default string is: “Kokkos::exclusive_scan_iterator_api_default”

  • for 5,6 the default string is: “Kokkos::exclusive_scan_view_api_default”

• first_from, last_from, first_dest:

  • range of elements to read from (*_from) and write to (first_dest)

  • must be random access iterators

  • must represent a valid range, i.e., last_from >= first_from (checked in debug mode)

  • must be accessible from exespace

• view_from, view_dest:

  • views to read elements from view_from and write to view_dest

  • must be rank-1, and have LayoutLeft, LayoutRight, or LayoutStride

  • must be accessible from exespace

• bin_op:

  • binary functor representing the operation to combine pair of elements. Must be valid to be called from the execution space passed, and callable with two arguments a,b of type (possible const) value_type, where value_type is the value type of InputIteratorType (for 1,2,5,6) or the value type of view_from (for 3,4,7,8), and must not modify a,b.

  • must conform to:

  struct BinaryOp
  {
     KOKKOS_INLINE_FUNCTION
     return_type operator()(const value_type & a,
                            const value_type & b) const {
       return /* ... */;
     }
  };
  

  The return type return_type must be such that an object of type OutputIteratorType for (1,2,5,6) or an object of type value_type where value_type is the value type of view_dest for (3,4,7,8) can be dereferenced and assigned a value of type return_type.

Return

Iterator to the element after the last element written.