What if you want additional re-planning strategies, e.g. location choice? You can implement such modules on your own and use them together with MATSim. You have two possibilities for creating your own re-planning module:

• Write the module in Java and make use of functionality provided by MATSim. In this case, you’re advised to integrate your module at code-level. This means you should be able to directly access and modify code of MATSim.
• Write the module in Java or any other language independently of MATSim. Your module should then run stand-alone. This way, you could also just write a wrapper to use existing code.

We will only look at the second possibility here. If you are interested in creating your module directly in MATSim, please have a look at the chapter “Creating a Custom Controler” to get an idea how and where you can include your own module.
Your external re-planning module must be an executable. MATSim will call your executable with the path of a configuration file as its only argument. Your executable thus must be able to parse MATSim configuration files in order to be used with MATSim. In the configuration file, the path to a plans file is set (module scenario, parameter inputPlansFilename) that contains the plans that your module should read and modify. A second parameter workingPlansFilename contains the path to a file where you must write the modified plans to. Additionally, workingEventsTxtFilename and networkFilename contains the paths to the events and network file which may be of use to your module.
To instruct MATSim to use your module for re-planning, you can add an entry to the configuration file. Have a look at the module strategy in examples/tutorial/externalReplanning.xml to see how MATSim can use external modules.
We provide for testing reasons a very simple external re-planning executable. The executable is a simple jar-file containing a single Java class. The example code just takes the given plans as input and writes them out unmodified to the specified output location. The source code for the example is available within the jar-file.
Run the provided example with the following command:

java -cp MATSim_r4776.jar org.matsim.run.Controler examples/tutorial/externalReplanning.xml

In the log, you should see entries that the external executable was called. Additionally, any output of the external executable is written to its own log file in the corresponding iteration-directory (output/ITERS/it.*/)