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C++ Template Library to Predict, Control, Learn Behaviors, and Represent Learnable Knowledge using On/Off Policy Reinforcement Learning
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(C++ Template Library to Predict, Control, Learn Behaviors, and Represent Learnable Knowledge using On/Off Policy Reinforcement Learning)

RLLib is a lightweight C++ template library that implements incremental, standard, and gradient temporal-difference learning algorithms in Reinforcement Learning. It is an optimized library for robotic applications and embedded devices that operates under fast duty cycles (e.g., < 30 ms). RLLib has been tested and evaluated on RoboCup 3D soccer simulation agents, physical NAO V4 humanoid robots, and Tiva C series launchpad microcontrollers to predict, control, learn behaviors, and represent learnable knowledge. The implementation of the RLLib library is inspired by the RLPark API, which is a library of temporal-difference learning algorithms written in Java.


  • Off-policy prediction algorithms:
    • GTD(λ)
    • GTD(λ)True
    • GQ(λ)
  • Off-policy control algorithms:
    • Q(λ)
    • Greedy-GQ(λ)
    • Softmax-GQ(λ)
    • Off-PAC (can be used in on-policy setting)
  • On-policy algorithms:
    • TD(λ)
    • TD(λ)AlphaBound
    • TD(λ)True
    • Sarsa(λ)
    • Sarsa(λ)AlphaBound
    • Sarsa(λ)True
    • Sarsa(λ)Expected
    • Actor-Critic (continuous actions, discrete actions, discounted reward settting, averaged reward settings, and so on)
  • Supervised learning algorithms:
    • Adaline
    • IDBD
    • KI
    • SemiLinearIDBD
    • Autostep
  • Policies: Random RandomX%Bias Greedy Epsilon-greedy Boltzmann Normal Softmax
  • Dot product: An efficient implementation of the dot product for tile coding based feature representations (with culling traces).
  • Benchmarking environments: Mountain Car Mountain Car 3D Swinging Pendulum Continuous Grid World Bicycle Cart Pole Acrobot Non-Markov Pole Balancing Helicopter
  • Optimization: Optimized for very fast duty cycles (e.g., with culling traces, RLLib has been tested on the Robocup 3D simulator agent, and on the NAO V4 (cognition thread)).
  • Usage: The algorithm usage is very much similar to RLPark, therefore, swift learning curve.
  • Examples: There are a plethora of examples demonstrating on-policy and off-policy control experiments.
  • Visualization: We provide a Qt4 based application to visualize benchmark problems.


Extension for Tiva C Series EK-TM4C123GXL LaunchPad, and Tiva C Series TM4C129 Connected LaunchPad microcontrollers.

Tiva C series launchpad microcontrollers:


Off-PAC ContinuousGridworld AverageRewardActorCritic SwingPendulum (Continuous Actions)


RLLib is a C++ template library. The header files are located in the include directly. You can simply include/add this directory from your projects, e.g., -I./include, to access the algorithms.

To access the control algorithms:

#include "ControlAlgorithm.h"

To access the predication algorithms:

#include "PredictorAlgorithm"

To access the supervised learning algorithms:

#include "SupervisedAlgorithm.h"

RLLib uses the namespace:

using namespace RLLib


RLLib provides a flexible testing framework. Follow these steps to quickly write a test case.

  • To access the testing framework: #include "HeaderTest.h"
#include "HeaderTest.h"


class YourTest Test: public YourTestBase
    YourTestTest() {}

    virtual ~Test() {}
    void run();

    void testYourMethod();

void YourTestBase::testYourMethod() {/** Your test code */}

void YourTestBase::run() { testYourMethod(); }
  • Add YourTest to the test/test.cfg file.
  • You can use @YourTest to execute only YourTest. For example, if you need to execute only MountainCar test cases, use @MountainCarTest.

Test Configuration

We are using CMAKE >= 2.8.7 to build and run the test suite.

  • mkdir build
  • cd build; cmake ..
  • make -j


RLLib provides a QT5 based Reinforcement Learning problems and algorithms visualization tool named RLLibViz. Currently RLLibViz visualizes following problems and algorithms:

  • On-policy:

    • SwingPendulum problem with continuous actions. We use AverageRewardActorCritic algorithm.
  • Off-policy:

    • ContinuousGridworld and MountainCar problems with discrete actions. We use Off-PAC algorithm.
  • In order to run the visualization tool, you need to have QT4.8 installed in your system.

  • In order to install RLLibViz:

    • Change directory to visualization/RLLibViz
    • qmake
    • make -j
    • ./RLLibViz


Operating Systems

  • Ubuntu >= 11.04
  • Windows (Visual Studio 2013)
  • Mac OS X


  • Variable action per state.
  • Non-linear algorithms.
  • Deep learning algorithms.



Saminda Abeyruwan, PhD (,

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