int serial_fib( int n)
{
if( n < 2)
return n;
else
return serial_fib( n - 1) + serial_fib( n - 2);
}
int parallel_fib( int n, int cutof)
{
if ( n < cutof) return serial_fib( n);
else
{
BOOST_ASSERT( boost::this_task::runs_in_pool() );
tsk::task< int > t1(
parallel_fib,
n - 1,
cutof);
tsk::task< int > t2(
parallel_fib,
n - 2,
cutof);
tsk::handle< int > h1(
tsk::async(
boost::move( t1),
tsk::as_sub_task() ) ) ;
tsk::handle< int > h2(
tsk::async(
boost::move( t2),
tsk::as_sub_task() ) );
return h1.get() + h2.get();
}
}
void operator()()const
{
// the result of this task, will be either set directly if < cutoff, otherwise when taks is ready
boost::asynchronous::continuation_result<long> task_res = this_task_result();
if (n_<cutoff_)
{
// n < cutoff => execute ourselves
task_res.set_value(serial_fib(n_));
}
else
{
// n> cutoff, create 2 new tasks and when both are done, set our result (res(task1) + res(task2))
boost::asynchronous::create_continuation_job<boost::asynchronous::any_serializable>(
// called when subtasks are done, set our result
[task_res](std::tuple<boost::future<long>,boost::future<long> > res)
{
long r = std::get<0>(res).get() + std::get<1>(res).get();
task_res.set_value(r);
},
// recursive tasks
fib_task(n_-1,cutoff_),
fib_task(n_-2,cutoff_));
}
}
long serial_fib( T n ) {
if( n<2 )
return n;
else
return serial_fib(n-1)+serial_fib(n-2);
}
