updated README

tsung-wei-huang · tsung-wei-huang · commit 4ac3518a8335 · 2018-08-26T14:45:00.000-05:00
diff --git a/README.md b/README.md
@@ -12,8 +12,7 @@ A fast C++ header-only library to help you quickly build parallel programs with
 # Why Cpp-Taskflow?
 
 Cpp-Taskflow lets you quickly build parallel dependency graphs using modern C++17.
-It is by far faster, more expressive, and easier for drop-in integration than existing libraries such as [OpenMP Tasking][OpenMP Tasking] and 
-[TBB FlowGraph][TBB FlowGraph].
+It is by far faster, more expressive, and easier for drop-in integration than existing libraries.
 
 | Without Cpp-Taskflow | With Cpp-Taskflow |
 | -------------------- | ----------------- |
@@ -476,12 +475,12 @@ The folder `example/` contains several examples and is a great place to learn to
 | [matrix.cpp](./example/matrix.cpp) | create two set of matrices and multiply each individually in parallel |
 | [parallel_for.cpp](./example/parallel_for.cpp)| parallelize a for loop with unbalanced workload |
 | [reduce.cpp](./example/reduce.cpp)| perform reduce operations over linear containers |
+| [subflow.cpp](./example/subflow.cpp)| create a taskflow graph that spawns dynamic tasks |
 
 
 # Get Involved
 + Report bugs/issues by submitting a [Github issue][Github issues].
 + Submit contributions using [pull requests][Github pull requests].
-+ Live chat and ask questions on [Gitter][Gitter].
 
 # Contributors
 Cpp-Taskflow is being actively developed and contributed by the following people:
diff --git a/example/subflow.cpp b/example/subflow.cpp
@@ -9,20 +9,40 @@
 // 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.hpp>  
 
-int main() {
+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.silent_emplace(
     // Task A
     [] () { std::cout << "TaskA\n"; },              
     // Task B
-    [cap=std::vector<int>{1,2,3,4,5,6,7,8}] (auto& subflow) {                             
+    [cap=std::vector<int>{1,2,3,4,5,6,7,8}, detached] (auto& subflow) {                             
 
-      std::cout << "TaskB\n";                                  
+      std::cout << "TaskB is spawning B1, B2, and B3 ...\n";
 
       auto B1 = subflow.silent_emplace([&]() { 
         printf("  Subtask B1: reduce sum = %d\n", 
@@ -41,6 +61,9 @@ int main() {
                                                               
       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"; },               
@@ -60,8 +83,8 @@ int main() {
                                    
   tf.dispatch().get();  // block until finished
 
-  // Now we can dump the topology
-  std::cout << tf.dump_topologies();
+  // examine the graph
+  std::cout << '\n' << tf.dump_topologies();
 
   return 0;
 }
