cpp-taskflow/example/subflow.cpp at master · Alzathar/cpp-taskflow · GitHub

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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;

}

cpp-taskflow/example/subflow.cpp at master · Alzathar/cpp-taskflow · GitHub

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