min_element¶
Header: <Kokkos_StdAlgorithms.hpp>
Finds the smallest element in a range or in a rank-1 View using either operator< to compare two elements or a user-provided comparison operator.
Warning
This is currently inside the Kokkos::Experimental namespace.
template <class ExecutionSpace, class IteratorType>
auto min_element(const ExecutionSpace& exespace, (1)
IteratorType first, IteratorType last);
template <class ExecutionSpace, class IteratorType>
auto min_element(const std::string& label, (2)
const ExecutionSpace& exespace,
IteratorType first, IteratorType last);
template <class ExecutionSpace, class IteratorType, class ComparatorType>
auto min_element(const ExecutionSpace& exespace, (3)
IteratorType first, IteratorType last,
ComparatorType comp);
template <class ExecutionSpace, class IteratorType, class ComparatorType>
auto min_element(const std::string& label, (4)
const ExecutionSpace& exespace,
IteratorType first, IteratorType last,
ComparatorType comp);
template <class ExecutionSpace, class DataType, class... Properties>
auto min_element(const ExecutionSpace& exespace, (5)
const ::Kokkos::View<DataType, Properties...>& view);
template <class ExecutionSpace, class DataType, class... Properties>
auto min_element(const std::string& label, (6)
const ExecutionSpace& exespace,
const ::Kokkos::View<DataType, Properties...>& view);
template <class ExecutionSpace, class DataType, class ComparatorType, class... Properties>
auto min_element(const ExecutionSpace& exespace, (7)
const ::Kokkos::View<DataType, Properties...>& view,
ComparatorType comp);
template <class ExecutionSpace, class DataType, class ComparatorType, class... Properties>
auto min_element(const std::string& label, (8)
const ExecutionSpace& exespace,
const ::Kokkos::View<DataType, Properties...>& view,
ComparatorType comp);
Overload set accepting a team handle¶
Added in version 4.2.
template <class TeamHandleType, class IteratorType>
KOKKOS_FUNCTION
auto min_element(const TeamHandleType& teamHandle, (9)
IteratorType first, IteratorType last);
template <class TeamHandleType, class DataType, class... Properties>
KOKKOS_FUNCTION
auto min_element(const TeamHandleType& teamHandle, (10)
const ::Kokkos::View<DataType, Properties...>& view);
template <class TeamHandleType, class IteratorType, class ComparatorType>
KOKKOS_FUNCTION
auto min_element(const TeamHandleType& teamHandle, (11)
IteratorType first, IteratorType last,
ComparatorType comp);
template <class TeamHandleType, class DataType, class ComparatorType,
class... Properties>
KOKKOS_FUNCTION
auto min_element(const TeamHandleType& teamHandle, (12)
const ::Kokkos::View<DataType, Properties...>& view,
ComparatorType comp);
Parameters and Requirements¶
exespace: execution space instance
teamHandle: team handle instance given inside a parallel region when using a TeamPolicy
label: string forwarded to internal parallel kernels for debugging purposes
1 and 3: The default string is “Kokkos::min_element_iterator_api_default”.
5 and 7: The default string is “Kokkos::min_element_view_api_default”.
NOTE: overloads accepting a team handle do not use a label internally
first, last: range of elements to examine
must be random access iterators, e.g., returned from Kokkos::Experimental::(c)begin/(c)end
must represent a valid range, i.e., last >= first (checked in debug mode)
must be accessible from exespace or from the execution space associated with the team handle
view: Kokkos view to examine
must be rank-1, and have LayoutLeft, LayoutRight, or LayoutStride
must be accessible from exespace or from the execution space associated with the team handle
comp:
binary functor returning true if the first argument is less than the second argument; comp(a,b) must be valid to be called from the execution space passed, and convertible to bool for every pair of arguments a,b of type value_type, where value_type is the value type of IteratorType (for 1,2,3,4) or the value type of view (for 5,6,7,8) and must not modify a,b.
must conform to:
struct Comparator
{
KOKKOS_INLINE_FUNCTION
bool operator()(const value_type & a, const value_type & b) const {
return /* true if a is less than b, based on your logic of "less than" */;
}
};
Returns iterator to the smallest element.
The following special cases apply:
if several elements are equivalent to the smallest element, it returns the iterator to the first such element.
if the range [first, last) is empty it returns last.
if view is empty, it returns Kokkos::Experimental::end(view).
namespace KE = Kokkos::Experimental;
Kokkos::View<double*> a("a", 13);
// fill a somehow
auto res = KE::min_element(Kokkos::DefaultExecutionSpace(), KE::begin(a), KE::end(a));
// passing the view directly
auto res = KE::min_element(Kokkos::DefaultExecutionSpace(), a);
// using a custom comparator
template <class ValueType1, class ValueType2 = ValueType1>
struct CustomLessThanComparator {
KOKKOS_INLINE_FUNCTION
bool operator()(const ValueType1& a,
const ValueType2& b) const {
// here we use < but one can put any custom logic to return true if a is less than b
return a < b;
}
KOKKOS_INLINE_FUNCTION
CustomLessThanComparator() {}
};
// passing the view directly
auto res = KE::min_element(Kokkos::DefaultExecutionSpace(), a, CustomLessThanComparator<double>());
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