Modeler¶

Create a module

First, you have to create a LSPModeler environment. It is the main class of the Modeler library and allows you to create a module in one of two ways:

• You can load a module from an existing LSP file with the method LSPModeler::loadModule().

• Or you can create an empty module with the method LSPModeler::createModule().

Both of these methods return an instance of LSPModule which will enable you to interact with the module’s variables and functions.

Launch a module

There are two launch modes for a module:

• Optimization mode: This is the classic and default mode for the modeler. At the very least, you must implement a model method in your LSP module that will build an LSModel. You can then call LSPModule::run() to start the execution of the module. This function takes as first argument a LocalSolver instance that you have to create beforehand using the LSPModeler::createSolver() method. After the LocalSolver model has been built, the resolution process will be started automatically.

  Note that the run method also accepts as a parameter a list of arguments that will be passed as global variables to your module:

  LSPModeler modeler;
  LocalSolver ls = modeler.createSolver();
  LSPModule module = modeler.loadModule("my_lsp_file.lsp");
  module.run(ls, {"lsIterationLimit=100", "lsTimeLimit=10"});
  

• Main mode: In this mode, the modeler behaves like a classical programming language. To use this mode, you have to implement a function named main in which you are free to do anything you want without being limited by the formalism of the functions input, model, param, display and output. You can then call LSPModule::runMain() to start the execution of the module.

  Note that unlike the optimization mode, it is your responsibility to manually create the solver instances, close your models and launch the resolutions. In return, you are free to run several successive resolutions or none at all if you just want to use LSP for its pure programming features.

For more details on the differences between the optimization and the main mode, read Main mode.

Interacting with variables

You can interact with the variables inside a module thanks to getters and setters on the LSPModule class. Values can be obtained in their native type or retrieved as LSPValue which is a container that can hold any type of value inside a module. For more information on value types available in the modeler you can look at LSPType.

You can create maps from the modeler instance with LSPModeler::createMap(). A Map is a data structure holding (key, value) pairs that can also be used as an array. For more information on maps you can look at the map module.

Using external functions

You can use your own C++ functions as LSP functions in the modeler thanks to the method LSPModeler::createFunction(). First you have to extend the LSPFunctor class and implement the call() function:

class MyLspFunction : public LSPFunctor {
    LSPValue call(LSPModeler& modeler, const std::vector<LSPValue>& arguments) {
        lsdouble result = arguments[0].asDouble() + arguments[1].asDouble();
        return modeler.createDouble(result);
    }
}

MyLspFunction myFunc;
LSPFunction lspFunc = modeler.createFunction(&myFunc);
LSPValue args[2] = {modeler.createDouble(1.5), modeler.createDouble(2.3)};
LSPvalue result = lspFunc.call(args, 2);
std::cout << "result = " << result.asDouble() << std::endl; // prints "result = 3.8"

In the snippet above we declare an LSP function that takes two LSP doubles as input, adds them together and returns the result. We can then call the function with LSPFunction::call() to execute the function and retrieve the result.

You can also assign the function to a variable in a module with LSPModule::setFunction(). After doing so, the function will be callable within any function of the module.