// This program demonstrates how to set priority to a task.

//

// Currently, Taskflow supports only three priority levels:

// + tf::TaskPriority::HIGH (numerical value = 0)

// + tf::TaskPriority::NORMAL (numerical value = 1)

// + tf::TaskPriority::LOW (numerical value = 2)

//

// Priority-based execution is non-preemptive. Once a task

// has started to execute, it will execute to completion,

// even if a higher priority task has been spawned or enqueued.

#include <taskflow/taskflow.hpp>

int main() {

// create an executor of only one worker to enable

// deterministic behavior

tf::Executor executor(1);

tf::Taskflow taskflow;

int counter {0};

// Here we create five tasks and print thier execution

// orders which should align with assigned priorities

auto [A, B, C, D, E] = taskflow.emplace(

[] () { },

[&] () {

std::cout << "Task B: " << counter++ << '\n'; // 0

},

[&] () {

std::cout << "Task C: " << counter++ << '\n'; // 2

},

[&] () {

std::cout << "Task D: " << counter++ << '\n'; // 1

},

[] () { }

);

A.precede(B, C, D);

E.succeed(B, C, D);

// By default, all tasks are of tf::TaskPriority::HIGH

B.priority(tf::TaskPriority::HIGH);

C.priority(tf::TaskPriority::LOW);

D.priority(tf::TaskPriority::NORMAL);

assert(B.priority() == tf::TaskPriority::HIGH);

assert(C.priority() == tf::TaskPriority::LOW);

assert(D.priority() == tf::TaskPriority::NORMAL);

// we should see B, D, and C in their priority order

executor.run(taskflow).wait();

}