1// Copyright 2020 The Marl Authors.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15// Simple "hello world" example that uses marl::Event and marl::WaitGroup.
16
17#include "marl/defer.h"
18#include "marl/event.h"
19#include "marl/scheduler.h"
20#include "marl/waitgroup.h"
21
22#include <cstdio>
23
24int main() {
25 // Create a marl scheduler using the 4 hardware threads.
26 // Bind this scheduler to the main thread so we can call marl::schedule()
27 marl::Scheduler::Config cfg;
28 cfg.setWorkerThreadCount(4);
29
30 marl::Scheduler scheduler(cfg);
31 scheduler.bind();
32 defer(scheduler.unbind()); // Automatically unbind before returning.
33
34 constexpr int numTasks = 10;
35
36 // Create an event that is manually reset.
37 marl::Event sayHello(marl::Event::Mode::Manual);
38
39 // Create a WaitGroup with an initial count of numTasks.
40 marl::WaitGroup saidHello(numTasks);
41
42 // Schedule some tasks to run asynchronously.
43 for (int i = 0; i < numTasks; i++) {
44 // Each task will run on one of the 4 worker threads.
45 marl::schedule([=] { // All marl primitives are capture-by-value.
46 // Decrement the WaitGroup counter when the task has finished.
47 defer(saidHello.done());
48
49 printf("Task %d waiting to say hello...\n", i);
50
51 // Blocking in a task?
52 // The scheduler will find something else for this thread to do.
53 sayHello.wait();
54
55 printf("Hello from task %d!\n", i);
56 });
57 }
58
59 sayHello.signal(); // Unblock all the tasks.
60
61 saidHello.wait(); // Wait for all tasks to complete.
62
63 printf("All tasks said hello.\n");
64
65 // All tasks are guaranteed to complete before the scheduler is destructed.
66}
67