is_partitioned

Header File: Kokkos_StdAlgorithms.hpp

namespace Kokkos{
namespace Experimental{

template <class ExecutionSpace, class InputIterator, class PredicateType>
bool is_partitioned(const ExecutionSpace& exespace,                              (1)
                    InputIterator first, InputIterator last,
                    PredicateType pred);

template <class ExecutionSpace, class InputIterator, class PredicateType>
bool is_partitioned(const std::string& label, const ExecutionSpace& exespace,    (2)
                    InputIterator first, InputIterator last,
                    PredicateType pred);

template <class ExecutionSpace, class DataType, class... Properties, class PredicateType>
auto is_partitioned(const ExecutionSpace& exespace,
                    const ::Kokkos::View<DataType, Properties...>& view,         (3)
                    PredicateType pred);

template <class ExecutionSpace, class DataType, class... Properties, class PredicateType>
auto is_partitioned(const std::string& label, const ExecutionSpace& exespace,
                    const ::Kokkos::View<DataType, Properties...>& view,         (4)
                    PredicateType pred);

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

Description

Returns true if all elements in the range [first, last) (1,2) or in view (3,4) satisfying the predicate pred appear before all elements that don’t. If [first, last) or view is empty, returns true.

Parameters and Requirements

• exespace:

  • execution space instance

• label:

  • used to name the implementation kernels for debugging purposes

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

  • for 3, the default string is: “Kokkos::is_partitioned_view_api_default”

• first, last:

  • range of elements to search in

  • must be random access iterators, e.g., Kokkos::Experimental::begin/end

  • must represent a valid range, i.e., last >= first (this condition is checked in debug mode)

  • must be accessible from exespace

• view:

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

  • must be accessible from exespace

• pred:

  • unary predicate returning true for the required element to replace; pred(v) must be valid to be called from the execution space passed, and convertible to bool for every argument v of type (possible const) value_type, where value_type is the value type of IteratorType (for 1,2) or the value type of view (for 3,4), and must not modify v.

  • must conform to:

  struct Predicate
  {
     KOKKOS_INLINE_FUNCTION
     bool operator()(const value_type & v) const { return /* ... */; }
  
     // or, also valid
  
     KOKKOS_INLINE_FUNCTION
     bool operator()(value_type v) const { return /* ... */; }
  };
  

Return

• true: if range is partitioned according to pred or if range is empty

• false: otherwise

Example

namespace KE = Kokkos::Experimental;

template<class ValueType>
struct IsNegative
{
  KOKKOS_INLINE_FUNCTION
  bool operator()(const ValueType & operand) const {
    constexpr auto zero = static_cast<ValueType>(0);
    return (operand < zero);
  }
};

using view_type = Kokkos::View<int*>;
view_type a("a", 15);
// fill a somehow

auto exespace  = Kokkos::DefaultExecutionSpace;
const auto res = KE::is_partitioned(exespace, KE::cbegin(a), KE::cend(a), IsNegative<int>());