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--- eeros_architecture:control_system:executor [2016/10/18 21:42] – created graf
+++ eeros_architecture:control_system:executor [2021/02/10 15:28] (current) – [Using the Executor] ursgraf
@@ Line 1: / Line 1: @@
 ====== Executor ======
-The executor is responsible to run various different time domains in seperated threads of execution.
+The executor is responsible to run various different time domains in separated threads of execution. The execution periods of different time domains are generally in a harmonic relationship to each other.
+===== Harmonic Tasks =====
+As the following figure shows each harmonic is run by its own thread of execution.
+{{ :eeros_architecture:control_system:executor.png?600 | }}
+In this example we have the safety system as the main task. It has the fastest execution period together with the time domain 1. The time domain 2 runs with the same period but only after time domain 1 has finished. Time domain 3 has a harmonic relationship to the main task with a ratio of 2.
+===== Using the Executor  ======
+First you have to define the executor.
+<code cpp>
+  eeros::Executor& executor = eeros::Executor::instance();
+</code>
+Next we have to define the main task. In general the main task will be the safety system.
+<code cpp>
+  SafetySystem ss(properties, 0.001); // runs every millisecond
+  executor.setMainTask(ss);
+</code>
+Now we create time domains and add it to the executor.
+<code cpp>
+  eeros::control::TimeDomain td1("td1", 0.001, true);
+  executor.add(td1);
+</code>
+This creates a time domain which should run in real-time with a period of 1 millisecond. Obviously the time domain has no blocks yet and therefore doesn't do any meaningful work yet.
+You could also create a periodic task as a separate object and assign it a time domain as follows.
+<code cpp>
+  eeros::control::TimeDomain td1("td1", 0.001, true);
+  eeros::task::Periodic per1("per1", 0.001, td1);
+  executor.add(per1);
+</code>
+Finally you have to start the executor with:
+<code cpp>
+  executor.run();
+</code>
+This call does not complete until you stop the main task with a special signal.
+IMPORTANT Please make sure to run an application using the executor with root privileges. This is necessary for the executor to be able to create threads with realtime priorities.
+===== Add More Time Domains ======
+The picture at the top of this page shows another two time domains. Time domain 2 runs after time domain 1. It can be created and added to time domain 1 as follows
+<code cpp>
+  eeros::control::TimeDomain td1("td1", 0.001, true);
+  eeros::task::Periodic per1("per1", 0.001, td1);
+  eeros::control::TimeDomain td2("td2", 0.001, true);
+  eeros::task::Periodic per2("per2", 0.001, td2);
+  per1.after.push_back(per2);
+  executor.add(per1);
+</code>
+Time domain 3 runs concurrently to time domain 1. It can therefore be created simply with
+<code cpp>
+  eeros::control::TimeDomain td3("td3", 0.002, true);
+  executor.add(td3);
+</code>