`transform_reduce`#

Header File: Kokkos_StdAlgorithms.hpp

namespace Kokkos{
namespace Experimental{

//
// overload set A
//
template <
  class ExecutionSpace, class IteratorType1,
  class IteratorType2, class ValueType>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (1)
                           IteratorType1 first1, IteratorType1 last1,
                           IteratorType2 first2,
                           ValueType init_reduction_value);

template <
  class ExecutionSpace, class IteratorType1,
  class IteratorType2, class ValueType>
ValueType transform_reduce(const std::string& label,                            (2)
                           const ExecutionSpace& exespace,
                           IteratorType1 first1, IteratorType1 last1,
                           IteratorType2 first2,
                           ValueType init_reduction_value);

template <
  class ExecutionSpace,
  class DataType1, class... Properties1,
  class DataType2, class... Properties2,
  class ValueType>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (3)
                           const ::Kokkos::View<DataType1, Properties1...>& first_view,
                           const ::Kokkos::View<DataType2, Properties2...>& second_view,
                           ValueType init_reduction_value);

template <
  class ExecutionSpace,
  class DataType1, class... Properties1,
  class DataType2, class... Properties2,
  class ValueType>
ValueType transform_reduce(const std::string& label,                            (4)
                           const ExecutionSpace& exespace,
                           const ::Kokkos::View<DataType1, Properties1...>& first_view,
                           const ::Kokkos::View<DataType2, Properties2...>& second_view,
                           ValueType init_reduction_value);

//
// overload set B
//
template <
  class ExecutionSpace,
  class IteratorType1, class IteratorType2,
  class ValueType,
  class BinaryJoinerType, class BinaryTransform>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (5)
                           IteratorType1 first1,
                           IteratorType1 last1, IteratorType2 first2,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           BinaryTransform binary_transformer);

template <
  class ExecutionSpace,
  class IteratorType1, class IteratorType2,
  class ValueType,
  class BinaryJoinerType, class BinaryTransform>
ValueType transform_reduce(const std::string& label,                            (6)
                           const ExecutionSpace& exespace,
                           IteratorType1 first1, IteratorType1 last1,
                           IteratorType2 first2,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           BinaryTransform binary_transformer);

template <
  class ExecutionSpace,
  class DataType1, class... Properties1,
  class DataType2, class... Properties2,
  class ValueType,
  class BinaryJoinerType, class BinaryTransform>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (7)
                           const ::Kokkos::View<DataType1, Properties1...>& first_view,
                           const ::Kokkos::View<DataType2, Properties2...>& second_view,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           BinaryTransform binary_transformer);

template <
   class ExecutionSpace,
   class DataType1, class... Properties1,
   class DataType2, class... Properties2,
   class ValueType,
   class BinaryJoinerType, class BinaryTransform>
ValueType transform_reduce(const std::string& label,                            (8)
                           const ExecutionSpace& exespace,
                           const ::Kokkos::View<DataType1, Properties1...>& first_view,
                           const ::Kokkos::View<DataType2, Properties2...>& second_view,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           BinaryTransform binary_transformer);

//
// overload set C
//
template <
  class ExecutionSpace,
  class IteratorType, class ValueType,
  class BinaryJoinerType, class UnaryTransform>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (9)
                           IteratorType first1, IteratorType last1,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           UnaryTransform unary_transformer);

template <
  class ExecutionSpace,
  class IteratorType, class ValueType,
  class BinaryJoinerType, class UnaryTransform>
ValueType transform_reduce(const std::string& label,
                           const ExecutionSpace& exespace,                      (10)
                           IteratorType first1, IteratorType last1,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           UnaryTransform unary_transformer);

template <
  class ExecutionSpace,
  class DataType, class... Properties, class ValueType,
  class BinaryJoinerType, class UnaryTransform>
ValueType transform_reduce(const ExecutionSpace& exespace,                      (11)
                           const ::Kokkos::View<DataType, Properties...>& first_view,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           UnaryTransform unary_transformer);

template <
  class ExecutionSpace,
  class DataType, class... Properties, class ValueType,
  class BinaryJoinerType, class UnaryTransform>
ValueType transform_reduce(const std::string& label,                            (12)
                           const ExecutionSpace& exespace,
                           const ::Kokkos::View<DataType, Properties...>& first_view,
                           ValueType init_reduction_value,
                           BinaryJoinerType joiner,
                           UnaryTransform unary_transformer);

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

Description#

(1,2): performs the product (via operator*) between each pair of elements in the range [first1, last1) and the range starting at first2, and reduces the results along with the initial value init_reduction_value
(3,4): performs the product (via operator*) between each pair of elements in first_view and second_view, and reduces the results along with the initial value init_reduction_value
(5,6): applies the functor binary_transformer to each pair of elements in the range [first1, last1) and the range starting at first2, and reduces the results along with the initial value init_reduction_value with the join operation done via the binary functor joiner
(7,8): applies the functor binary_transformer to each pair of elements in first_view and second_view, and reduces the result along with the initial value init_reduction_value with the join operation done via the binary functor joiner
(9,10): applies the functor unary_transformer to each element in the range [first, last), and reduces the results along with the initial value init_reduction_value with the join operation done via the binary functor joiner
(11,12): applies the functor unary_transformer to each element in view, and reduces the results along with the initial value init_reduction_value with the join operation done via the binary functor joiner

Parameters and Requirements#

exespace:
- execution space instance
label:
- used to name the implementation kernels for debugging purposes
- for 1,5,9 the default string is: “Kokkos::transform_reduce_iterator_api_default”
- for 3,7,11 the default string is: “Kokkos::transform_reduce_view_api_default”
first1, last1, first2:
- ranges of elements to transform and reduce
- must be random access iterators
- must represent a valid range, i.e., last1 >= first1 (checked in debug mode)
- must be accessible from exespace
first_view, second_view:
- views to transform and reduce
- must be rank-1, and have LayoutLeft, LayoutRight, or LayoutStride
- must be accessible from exespace
init_reduction_value:
- initial reduction value to use
joiner:
- binary functor performing the desired operation to join two elements. Must be valid to be called from the execution space passed, and callable with two arguments a,b of type (possible const) ValueType, and must not modify a,b.
- Must conform to:
```
struct JoinFunctor {
  KOKKOS_FUNCTION
  constexpr ValueType operator()(const ValueType& a,
                               const ValueType& b) const {
    return /* ... */
  }
};
```
- The behavior is non-deterministic if the joiner operation is not associative or not commutative.
binary_transformer:
- binary functor applied to each pair of elements before doing the reduction. Must be valid to be called from the execution space passed, and callable with two arguments a,b of type (possible const) value_type_a and value_type_b, where value_type_{a,b} are the value types of first1 and first2 (for 1,2,5,6) or the value types of first_view and second_view (for 3,4,7,8), and must not modify a,b.
- Must conform to:
```
struct BinaryTransformer {
  KOKKOS_FUNCTION
  constexpr return_type operator()(const value_type_a & a, const value_type_b & b) const {
    return /* ... */
  }
};
```
- the return_type is such that it can be accepted by the joiner
unary_transformer:
- unary functor performing the desired operation to an element. Must be valid to be called from the execution space passed, and callable with an arguments v of type (possible const) value_type, where value_type is the value type of first1 (for 9,10) or the value type of first_view (for 11,12), and must not modify v.
- Must conform to:
```
struct UnaryTransformer {
  KOKKOS_FUNCTION
  constexpr value_type operator()(const value_type & v) const {
    return /* ... */
  }
};
```

Return#

The reduction result.

transform_reduce#

Description#

Parameters and Requirements#

Return#

`transform_reduce`#