dataflow_cpp: moved processing of sources to worker threads

dataflow_cpp/include/embb/dataflow/internal/scheduler.h

@@ -46,6 +46,9 @@ class Scheduler {
     int process_id,
     Action & action,
     embb::mtapi::ExecutionPolicy const & policy) = 0;
+  virtual void Run(
+    Action & action,
+    embb::mtapi::ExecutionPolicy const & policy) = 0;
   virtual void WaitForSlice(int slice) = 0;
   virtual int GetSlices() = 0;
 };

dataflow_cpp/include/embb/dataflow/internal/scheduler_mtapi.h

@@ -105,6 +105,16 @@ class SchedulerMTAPI : public Scheduler {
     group_[idx].Start(job_, &action, static_cast<void*>(NULL),
       task_attr);
   }
+  virtual void Run(
+    Action & action,
+    embb::mtapi::ExecutionPolicy const & policy) {
+    embb::mtapi::Node & node = embb::mtapi::Node::GetInstance();
+    embb::mtapi::TaskAttributes task_attr;
+    task_attr.SetPolicy(policy);
+    embb::mtapi::Task task = node.Start(job_, &action, static_cast<void*>(NULL),
+      task_attr);
+    task.Wait();
+  }
   virtual void Enqueue(
     int process_id,
     Action & action,

dataflow_cpp/include/embb/dataflow/internal/scheduler_sequential.h

@@ -43,6 +43,11 @@ class SchedulerSequential : public Scheduler {
     embb::mtapi::ExecutionPolicy const &) {
     action.RunSequential();
   }
+  virtual void Run(
+    Action & action,
+    embb::mtapi::ExecutionPolicy const &) {
+    action.RunSequential();
+  }
   virtual void Enqueue(
     int,
     Action & action,

dataflow_cpp/include/embb/dataflow/internal/source.h

@@ -67,7 +67,8 @@ class Source< Outputs<O1, O2, O3, O4, O5> >
 
   virtual bool Start(int clock) {
     if (not_done_) {
-      Run(clock);
+      Action act(this, clock);
+      sched_->Run(act, embb::mtapi::ExecutionPolicy());
     }
     return not_done_;
   }

dataflow_cpp/test/dataflow_cpp_test_simple.cc

@@ -155,6 +155,7 @@ void SimpleTest::TestBasic() {
   embb::base::CoreSet core_set(true);
   embb::mtapi::NodeAttributes node_attr;
   node_attr
+    .SetReuseMainThread(MTAPI_TRUE)
     .SetCoreAffinity(core_set)
     .SetMaxQueues(2);
   embb::mtapi::Node::Initialize(