hpx::future<FwdIter>
rotate_helper(ExPolicy const& policy, FwdIter first, FwdIter new_first,
FwdIter last)
{
typedef boost::mpl::false_ non_seq;
task_execution_policy p =
task(policy.get_executor(), policy.get_chunk_size());
detail::reverse r;
return lcos::local::dataflow(
hpx::util::unwrapped([=]() mutable {
hpx::future<void> f = r.call(p, first, last, non_seq());
std::advance(first, std::distance(new_first, last));
return f.then(
[first] (hpx::future<void> &&) -> FwdIter
{
return first;
});
}),
r.call(p, first, new_first, non_seq()),
r.call(p, new_first, last, non_seq()));
}
// requires traits::is_future<Future>
std::size_t get_static_chunk_size(ExPolicy policy,
std::vector<Future>& workitems,
F1 && f1, FwdIter& first, std::size_t& count,
std::size_t chunk_size)
{
if (chunk_size == 0)
{
chunk_size = policy.get_chunk_size();
if (chunk_size == 0)
{
typedef typename ExPolicy::executor_type executor_type;
std::size_t const cores = executor_traits<executor_type>::
os_thread_count(policy.executor());
if (count > 100*cores)
chunk_size = auto_chunk_size(workitems, f1, first, count);
if (chunk_size == 0)
chunk_size = (count + cores - 1) / cores;
}
}
return chunk_size;
}