parallel_for_each Body semantics and requirements#
Description#
This page clarifies ParallelForEachBody
named requirements for tbb::parallel_for_each algorithm specification.
namespace oneapi {
namespace tbb {
template <typaname InputIterator, typename Body>
void parallel_for_each( InputIterator first, InputIterator last, Body body ); // overload (1)
template <typename InputIterator, typename Body>
void parallel_for_each( InputIterator first, InputIterator last, Body body, task_group_context& group ); // overload (2)
template <typename Container, typename Body>
void parallel_for_each( Container& c, Body body ); // overload (3)
template <typename Container, typename Body>
void parallel_for_each( Container& c, Body body, task_group_context& group ); // overload (4)
template <typename Container, typename Body>
void parallel_for_each( const Container& c, Body body ); // overload (5)
template <typename Container, typename Body>
void parallel_for_each( const Container& c, Body body, task_group_context& group ); // overload (6)
} // namespace tbb
} // namespace oneapi
Terms#
iteratordetermines the type of the iterator passed intoparallel_for_eachalgorithm (which isInputIteratorfor overloads (1) and (2) anddecltype(std::begin(c))for overloads (3) - (6))value_type- the typetypename std::iterator_traits<iterator>::value_typereference- the typetypename std::iterator_traits<iterator>::reference.
Requirements for different iterator types#
If the iterator satisfies Input iterator named requirements from [input.iterators] ISO C++ Standard section and do not satisfies
Forward iterator named requirements from [forward.iterators] ISO C++ Standard section, tbb::parallel_for_each requires the execution
of the body with an object of type const value_type& or value_type&& to be well-formed. If both forms are well-formed, an overload with
rvalue reference will be preferred.
Caution
If the Body only takes non-const lvalue reference to value_type, named requirements above are violated and the program can be ill-formed.
If the iterator satisfies Forward iterator named requirements from [forward.iterators] ISO C++ Standard section, tbb::parallel_for_each requires the execution of the body
with an object of type reference to be well-formed.
Requirements for Body with feeder argument#
Additional elements submitted into tbb::parallel_for_each through the feeder::add passes to the Body as rvalues and therefore the corresponding
execution of the Body is required to be well-formed.