Libsumo

# Libsumo

The main way to interact with a running simulation is TraCI which gives the complete flexibility of doing cross-platform, cross-language, and networked interaction with sumo acting as a server. One major drawback is the communication overhead due to the protocol and the socket communication. To have a more efficient coupling without the need for socket communication, the TraCI API is provided as a C++ library with the following properties:

- C++ interface based on static functions and a few simple wrapper classes for results which can be linked directly to the client code
- Function signatures similar to TraCI
- Pre-built language bindings for Java and Python (using SWIG)
- Support for other programming languages via SWIG

# Limitations

The following things currently do not work (or work differently than with the TraCI Python client):

- running with sumo-gui does not work on Windows and is still highly experimental on other platforms
- subscriptions that require additional arguments (except for vehicle.getLeader)
- stricter type checking
  - the TraCI client sometimes accepts any iterable object where Libsumo wants a list
  - TraCI client may accept any object where Libsumo needs a boolean value
  - TraCI automatically converts every parameter into a string if a string is needed, Libsumo does not
- using traci.init or traci.connect is not possible (you always need to use traci.start / libsumo.start)
- with traci every TraCIException will generate a message on stderr, Libsumo does not generate this message

# Building it

It currently requires cmake and swig being installed together with the developer packages for Python (and Java if needed), for Windows see Windows CMake. You need to (re-)compile sumo yourself under Windows following the remarks above, under Linux see Installing/Linux_Build (it is probably just a matter of calling cmake and make again if you previously did a build without swig). For the python bindings you will get a libsumo.py and a _libsumo.so (or .pyd on Windows). If you place them somewhere on your python path you should be able to use them as described below.

Note

Make sure to add `"/your/path/to/sumo/tools"` to the `PYTHONPATH` environment variable.

# Using libsumo

If you want to use the (experimental) GUI then you need to have `sumo-gui` in your start command instead of `sumo` or define the environment variable `LIBSUMO_GUI`.

## Python

    import libsumo
    libsumo.start(["sumo", "-c", "test.sumocfg"])
    libsumo.simulationStep()

Existing traci scripts can be reused (subject to the limitations mentioned above) by calling

    import libsumo as traci

In case you have a lot of scripts you can also set the environment variable `LIBSUMO_AS_TRACI` to a non empty value which will trigger the import as above.

## C++

Please note the extra `#define` for enabling GUI code which is not needed if you do not or cannot use the GUI (Windows).

### Example Code (test.cpp)

    #include <iostream>
    #define HAVE_LIBSUMOGUI  // if you are on Windows or have libsumo compiled yourself without GUI you should remove this line
    #include <libsumo/libsumo.h>

    using namespace libsumo;

    int main(int argc, char* argv[]) {
        Simulation::load({"-c", "test.sumocfg"});
        for (int i = 0; i < 5; i++) {
            Simulation::step();
        }
        Simulation::close();
    }

### compiling on Linux (make sure SUMO_HOME is set and sumo has been built)

    g++ -o test -std=c++11 -I$SUMO_HOME/src test.cpp -L$SUMO_HOME/bin -lsumocpp

### running on Linux

    LD_LIBRARY_PATH=$SUMO_HOME/bin ./test

## Java

You might want to use the available Maven package.

### Example Code (Test.java)

    import org.eclipse.sumo.libsumo.Simulation;
    import org.eclipse.sumo.libsumo.StringVector;

    public class Test {
        public static void main(String[] args) {
            System.loadLibrary("libsumojni");
            Simulation.load(new StringVector(new String[] {"-c", "test.sumocfg"}));
            for (int i = 0; i < 5; i++) {
                Simulation.step();
            }
            Simulation.close();
        }
    }

### compiling on Linux (make sure SUMO_HOME is set and sumo has been built)

    javac -cp $SUMO_HOME/bin/libsumo-1.8.0-SNAPSHOT.jar Test.java

### running on Linux

    java -Djava.library.path=$SUMO_HOME/bin -cp $SUMO_HOME/bin/libsumo-1.8.0-SNAPSHOT.jar:. Test

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