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92 lines (70 loc) · 2.77 KB
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// This example demonstrates how to use cpp-taskflow to create
// dynamic workload during execution.
//
// We first create four tasks A, B, C, and D. During the execution
// of B, it uses flow builder to creates another three tasks
// B1, B2, and B3, and adds dependencies from B1 and B2 to B3.
//
// We use dispatch and get to wait until the graph finished.
// Do so is difference from "wait_for_all" which will clean up the
// finished graphs. After the graph finished, we dump the topology
// for inspection.
//
// Usage: ./subflow detach|join
//
#include <taskflow/taskflow.hpp>
const auto usage = "usage: ./subflow detach|join";
int main(int argc, char* argv[]) {
if(argc != 2) {
std::cerr << usage << std::endl;
std::exit(EXIT_FAILURE);
}
std::string_view opt(argv[1]);
if(opt != "detach" && opt != "join") {
std::cerr << usage << std::endl;
std::exit(EXIT_FAILURE);
}
auto detached = (opt == "detach") ? true : false;
// Create a taskflow graph with three regular tasks and one subflow task.
tf::Taskflow tf(std::thread::hardware_concurrency());
auto [A, B, C, D] = tf.emplace(
// Task A
[] () { std::cout << "TaskA\n"; },
// Task B
[cap=std::vector<int>{1,2,3,4,5,6,7,8}, detached] (auto& subflow) {
std::cout << "TaskB is spawning B1, B2, and B3 ...\n";
auto B1 = subflow.emplace([&]() {
printf(" Subtask B1: reduce sum = %d\n",
std::accumulate(cap.begin(), cap.end(), 0, std::plus<int>()));
}).name("B1");
auto B2 = subflow.emplace([&]() {
printf(" Subtask B2: reduce multiply = %d\n",
std::accumulate(cap.begin(), cap.end(), 1, std::multiplies<int>()));
}).name("B2");
auto B3 = subflow.emplace([&]() {
printf(" Subtask B3: reduce minus = %d\n",
std::accumulate(cap.begin(), cap.end(), 0, std::minus<int>()));
}).name("B3");
B1.precede(B3);
B2.precede(B3);
// detach or join the subflow (by default the subflow join at B)
if(detached) subflow.detach();
},
// Task C
[] () { std::cout << "TaskC\n"; },
// Task D
[] () { std::cout << "TaskD\n"; }
);
A.name("A");
B.name("B");
C.name("C");
D.name("D");
A.precede(B); // B runs after A
A.precede(C); // C runs after A
B.precede(D); // D runs after B
C.precede(D); // D runs after C
tf.dispatch().get(); // block until finished
// examine the graph
std::cout << '\n' << tf.dump_topologies();
return 0;
}