Getting Started with the Function Manager in WRENCH

The FunctionManager in WRENCH is a critical component designed to manage and coordinate the execution of functions in a simulation environment. In this post, we’ll explore how to get started with implementing and using the FunctionManager, along with tips for registering and managing functions.

Understanding the FunctionManager

The FunctionManager is part of the WRENCH simulation framework and is responsible for managing functions and their execution within the simulation. It inherits from the Service class, making it part of the simulation’s service hierarchy.

Key features of the FunctionManager include:

• Registration of functions: It provides the ability to register functions that can be called during simulation.
• Management of execution: The FunctionManager handles execution requests and ensures the appropriate functions are executed.

Before diving into the implementation, ensure you have the following:

1. A working installation of WRENCH.
2. Familiarity with the concepts of services in WRENCH.
3. A development environment with necessary dependencies (e.g., CMake, SimGrid).

Implementing the FunctionManager

If you encounter an error like invalid new-expression of abstract class type 'wrench::FunctionManager', it indicates that the FunctionManager class has pure virtual methods that need to be implemented.

To resolve this issue, you should either:

• Provide concrete implementations for all pure virtual methods in the FunctionManager class.
• Use a derived class that implements the pure virtual methods of FunctionManager.

Here is a quick guide to implementing the FunctionManager:

Step 1: Create a Derived Class

Create a subclass of FunctionManager that implements all its abstract methods. For example:

#include "FunctionManager.h"

class MyFunctionManager : public wrench::FunctionManager {
public:
    MyFunctionManager(const std::string &hostname, wrench::S4U_CommPort *commport)
        : FunctionManager(hostname, commport) {}

    void main() override {
        // Implementation of the main function.
    }

    // Implement other pure virtual methods if any.
};

Step 2: Instantiate the Derived Class

In your code, replace the instantiation of FunctionManager with your derived class:

new MyFunctionManager(this->hostname, this->commport);

Step 3: Implement the Logic

Define the behavior of your main() method and other necessary functions in MyFunctionManager. The main() method typically contains the logic for the service’s behavior.

Registering Functions

Once your FunctionManager is implemented, you can register functions with it. Here’s how you can do it:

Step 1: Define the Function

Define the function you want to register. For example:

void myFunction() {
    // Your function logic here.
}

Step 2: Register the Function

Use the registerFunction() method provided by FunctionManager to register the function:

myFunctionManager->registerFunction("my_function", myFunction);

Step 3: Call the Function

To execute a registered function, use the appropriate call mechanism provided by the FunctionManager:

myFunctionManager->executeFunction("my_function");

Tips for Debugging

1. Undefined References: Ensure all pure virtual methods in the FunctionManager class are implemented in your derived class.
2. Linker Errors: If you encounter linker errors, check that all necessary files are included in your build system (e.g., CMakeLists.txt).
3. Runtime Issues: Use logging or debugging tools to trace execution flow within the FunctionManager.

Conclusion

The FunctionManager is a powerful tool for managing functions in WRENCH simulations. By implementing a derived class and registering your functions, you can extend its capabilities and tailor it to your specific needs. With these steps, you’re well on your way to creating sophisticated and robust simulation services.

Feel free to reach out if you have any questions or run into issues while working with the FunctionManager. Happy coding!