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# Parallel Tasking Library (PTL)
Lightweight C++11 multithreading tasking system featuring thread-pool, task-groups, and lock-free task queue
## Basic Interface
```cpp
#include "PTL/PTL.hh"
#include <cassert>
inline long
fibonacci(long n)
{
return (n < 2) ? n : (fibonacci(n - 1) + fibonacci(n - 2));
}
int main()
{
bool use_tbb = false;
auto num_threads = 4;
auto run_manager = PTL::TaskRunManager(use_tbb);
run_manager.Initialize(num_threads);
auto* task_manager = run_manager.GetTaskManager();
// add a task via the task manager
auto baz = task_manager->async<long>(fibonacci, 40);
// functor to combine results
auto join = [](long& lhs, long rhs) { return lhs += rhs; };
// create a task group for 10 fibonacci calculations
PTL::TaskGroup<long> foo(join);
for(uint64_t i = 0; i < 10; ++i)
foo.exec(fibonacci, 40);
// create a task group for 10 fibonacci calculations
PTL::TaskGroup<void> bar{};
long ret_bar = 0;
auto run = [&ret_bar](long n) { ret_bar += fibonacci(n); };
for(uint64_t i = 0; i < 10; ++i)
bar.exec(run, 40);
auto ret_baz = baz->get();
auto ret_foo = foo.join();
bar.join();
assert(ret_baz * 10 == ret_foo);
assert(ret_baz * 10 == ret_bar);
assert(ret_foo == ret_bar);
}
```
## Explicit Thread-Pool
Using `PTL::TaskRunManager` is not necessary with task-groups.
You can create new thread-pools directly and pass them to task-groups:
```cpp
long example()
{
// create a new thread-pool explicitly
PTL::ThreadPool tp(4);
// combines results
auto join = [](long& lhs, long rhs) { return lhs += rhs; };
// specify thread-pool explicitly
PTL::TaskGroup<long> foo(join, &tp);
for(int i = 0; i < 10; ++i)
foo.exec(fibonacci, 40);
// blocks until tasks in group are completed
// thread-pool is destroyed after function returns
return foo.get();
}
```
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