Counting 1,868 Big Data & Machine Learning Frameworks, Toolsets, and Examples...
Suggestion? Feedback? Tweet @stkim1

Last Commit
Oct. 18, 2017
Jun. 6, 2017

ELF: An Extensive, Lightweight and Flexible Platform for Game Research


ELF is an Extensive, Lightweight and Flexible platform for game research, in particular for real-time strategy (RTS) games. On the C++-side, ELF hosts multiple games in parallel with C++ threading. On the Python side, ELF returns one batch of game state at a time, making it very friendly for modern RL. In comparison, other platforms (e.g., OpenAI Gym) wraps one single game instance with one Python interface. This makes concurrent game execution a bit complicated, which is a requirement of many modern reinforcement learning algorithms.

Besides, ELF now also provides a Python version for running concurrent game environments, by Python multiprocessing with ZeroMQ inter-process communication. See ./ for a simple example.

For research on RTS games, ELF comes with an fast RTS engine, and three concrete environments: MiniRTS, Capture the Flag and Tower Defense. MiniRTS has all the key dynamics of a real-time strategy game, including gathering resources, building facilities and troops, scouting the unknown territories outside the perceivable regions, and defend/attack the enemy. User can access its internal representation and can freely change the game setting.


ELF has the following characteristics:

  • End-to-End: ELF offers an end-to-end solution to game research. It provides miniature real-time strategy game environments, concurrent simulation, intuitive APIs, web-based visualzation, and also comes with a reinforcement learning backend empowered by Pytorch with minimal resource requirement.

  • Extensive: Any game with C/C++ interface can be plugged into this framework by writing a simple wrapper. As an example, we already incorporate Atari games into our framework and show that the simulation speed per core is comparable with single-core version, and is thus much faster than implementation using either multiprocessing or Python multithreading. In the future, we plan to incorporate more environments, e.g., DarkForest Go engine.

  • Lightweight: ELF runs very fast with minimal overhead. ELF with a simple game (MiniRTS) built on RTS engine runs 40K frame per second per core on a MacBook Pro. Training a model from scratch to play MiniRTS takes a day on 6 CPU + 1 GPU.

  • Flexible: Pairing between environments and actors is very flexible, e.g., one environment with one agent (e.g., Vanilla A3C), one environment with multiple agents (e.g., Self-play/MCTS), or multiple environment with one actor (e.g., BatchA3C, GA3C). Also, any game built on top of the RTS engine offers full access to its internal representation and dynamics. Besides efficient simulators, we also provide a lightweight yet powerful Reinforcement Learning framework. This framework can host most existing RL algorithms. In this open source release, we have provided state-of-the-art actor-critic algorithms, written in PyTorch.

Supported Environments

Any game with C/C++ interface can be plugged into this framework by writing a simple wrapper. Currently we have the following environment:

  1. MiniRTS and its extensions (./rts)
    A miniature real-time strategy game that captures the key dynamics of its genre, including building workers, collecting resources, exploring unseen territories, defend the enemy and attack them back. The game runs extremely fast (40K FPS per core on a laptop) to faciliate the usage of many existing on-policy reinforcement learning approaches.

  2. Atari games (./atari)
    We incorporate Arcade Learning Environment (ALE) into ELF so that you can load any rom and run 1000 concurrent game instances easily.

  3. Go engine (./go)
    We reimplement our DarkForest Go engine in ELF platform. Now you can easily load a bunch of .sgf files and train your own Go AI with minimal resource requirements (i.e., a single GPU plus a week).


When you use ELF, please reference the paper with the following BibTex entry:

ELF: An Extensive, Lightweight and Flexible Research Platform for Real-time Strategy Games
Yuandong Tian, Qucheng Gong, Wenling Shang, Yuxin Wu, C. Lawrence Zitnick
NIPS 2017

  title={ELF: An Extensive, Lightweight and Flexible Research Platform for Real-time Strategy Games},
  author={Yuandong Tian and Qucheng Gong and Wenling Shang and Yuxin Wu and C. Lawrence Zitnick},
  journal={Advances in Neural Information Processing Systems (NIPS)},

Relevant Materials

Slides in ICML Video Games and Machine Learning (VGML) workshop.

Demo. Top-left is trained bot while bottom-right is rule-based bot.


Check here for detailed documentation. You can also compile your version in ./doc using sphinx.

Basic Usage

ELF is very easy to use. The initialization looks like the following:

# We run 1024 games concurrently.
num_games = 1024

# Wait for a batch of 256 games.
batchsize = 256  

# The return states contain key 's', 'r' and 'terminal'
# The reply contains key 'a' to be filled from the Python side.
# The definitions of the keys are in the wrapper of the game.  
input_spec = dict(s='', r='', terminal='')
reply_spec = dict(a='')

context = Init(num_games, batchsize, input_spec, reply_spec)

The main loop is also very simple:

# Start all game threads and enter main loop.
while True:
    # Wait for a batch of game states to be ready
    # These games will be blocked, waiting for replies.
    batch = context.Wait()

    # Apply a model to the game state. The output has key 'pi'
    # You can do whatever you want here. E.g., applying your favorite RL algorithms.
    output = model(batch)

    # Sample from the output to get the actions of this batch.
    reply['a'][:] = SampleFromDistribution(output)

    # Resume games.

# Stop all game threads.

Please check and for actual runnable codes.


C++ compiler with C++11 support (e.g., gcc >= 4.9) is required. The following libraries are required tbb. CMake is also required.

Python 3.x is required. In addition, you need to install following package: PyTorch version 0.2.0+, tqdm, zmq, msgpack, msgpack_numpy

How to train

To train a model for MiniRTS, please first compile ./rts/game_MC (See the instruction in ./rts/ using cmake). Note that a compilation of ./rts/backend is not necessary for training, unless you want to see visualization.

Then please run the following commands in the current directory (you can also reference

game=./rts/game_MC/game model=actor_critic model_file=./rts/game_MC/model \ 
    --num_games 1024 --batchsize 128                                                                  # Set number of games to be 1024 and batchsize to be 128.  
    --freq_update 50                                                                                  # Update behavior policy after 50 updates of the model.
    --players "fs=50,type=AI_NN,args=backup/AI_SIMPLE|delay/0.99|start/500;fs=20,type=AI_SIMPLE"      # Specify AI and its opponent, separated by semicolon. `fs` is frameskip that specifies How often your opponent makes a decision (e.g., fs=20 means it acts every 20 ticks)
                                                                                                      # If `backup` is specified in `args`, then we use rule-based AI for the first `start` ticks, then trained AI takes over. `start` decays with rate `decay`. 
    --tqdm                                                                  # Show progress bar.
    --gpu 0                                                                 # Use first gpu. If you don't specify gpu, it will run on CPUs. 
    --T 20                                                                  # 20 step actor-critic
    --additional_labels id,last_terminal         
    --trainer_stats winrate                                                 # If you want to see the winrate over iterations. 
                                                                            # Note that the winrate is computed when the action is sampled from the multinomial distribution (not greedy policy). 
                                                                            # To evaluate your model more accurately, please use

Note that long horizon (e.g., --T 20) could make the training much faster and (at the same time) stable. With long horizon, you should be able to train it to 70% winrate within 12 hours with 16CPU and 1GPU. You can control the number of CPUs used in the training using taskset -c.

Here is one trained model with 80% winrate against AI_SIMPLE for frameskip=50. Here is one game replay.

The following is a sample output during training:

Version:  bf1304010f9609b2114a1adff4aa2eb338695b9d_staged
Num Actions:  9
Num unittype:  6
100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 5000/5000 [01:35<00:00, 52.37it/s]
[2017-07-12 09:04:13.212017][128] Iter[0]:
Train count: 820/5000, actor count: 4180/5000
Save to ./
Filename = ./save-820.bin
Command arguments --batchsize 128 --freq_update 50 --fs_opponent 20 --latest_start 500 --latest_start_decay 0.99 --num_games 1024 --opponent_type AI_SIMPLE --tqdm
0:acc_reward[4100]: avg: -0.34079, min: -0.58232[1580], max: 0.25949[185]
0:cost[4100]: avg: 2.15912, min: 1.97886[2140], max: 2.31487[1173]
0:entropy_err[4100]: avg: -2.13493, min: -2.17945[438], max: -2.04809[1467]
0:init_reward[820]: avg: -0.34093, min: -0.56980[315], max: 0.26211[37]
0:policy_err[4100]: avg: 2.16714, min: 1.98384[1520], max: 2.31068[1176]
0:predict_reward[4100]: avg: -0.33676, min: -1.36083[1588], max: 0.39551[195]
0:reward[4100]: avg: -0.01153, min: -0.13281[1109], max: 0.04688[124]
0:rms_advantage[4100]: avg: 0.15646, min: 0.02189[800], max: 0.79827[564]
0:value_err[4100]: avg: 0.01333, min: 0.00024[800], max: 0.06569[1549]

 86%|████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████▉                    | 4287/5000 [01:23<00:15, 46.97it/s]

To evaluate a model for MiniRTS, try the following command (you can also reference

game=./rts/game_MC/game model=actor_critic model_file=./rts/game_MC/model \ 
    --load [your model]
    --batchsize 128 
    --players "fs=50,type=AI_NN;fs=20,type=AI_SIMPLE"  
    --num_games 1024 
    --num_eval 10000
    --tqdm                          # Nice progress bar
    --gpu 0                         # Use GPU 0 as the evaluation gpu.
    --additional_labels id          # Tell the game environment to output additional dict entries.
    --greedy                        # Use greedy policy to evaluate your model. If not specified, then it will sample from the action distributions. 

Here is an example output (it takes 1 min 40 seconds to evaluate 10k games with 12 CPUs):

Version:  dc895b8ea7df8ef7f98a1a031c3224ce878d52f0_
Num Actions:  9
Num unittype:  6
Load from ./save-212808.bin
Version:  dc895b8ea7df8ef7f98a1a031c3224ce878d52f0_
Num Actions:  9
Num unittype:  6
100%|████████████████████████████████████████████████████████████████████████████████████████████| 10000/10000 [01:40<00:00, 99.94it/s]
str_acc_win_rate: Accumulated win rate: 0.735 [7295/2628/9923]
best_win_rate: 0.7351607376801297
new_record: True
count: 0
str_win_rate: [0] Win rate: 0.735 [7295/2628/9923], Best win rate: 0.735 [0]
Stop all game threads ...


Try the following script if you want to do self-play in Minirts. It will start with two bots, both starting with the pre-trained model. One bot will be trained over time, while the other is held fixed. If you just want to check their winrate without training, try --actor_only.

sh ./ [your pre-trained model] 


To visualize a trained bot, you can specify --save_replay_prefix [replay_file_prefix] whn running to save (lots of) replays. Note that the same flag can also be applied to training/selfplay.

All replay files contain action sequences, are in .rep and should reproduce the exact same game when loaded. To load the replay in the command line, using the following:

./minirts-backend replay --load_replay [your replay] --vis_after 0

and open the webpage ./rts/frontend/minirts.html to check the game. To load and run the replay in the command line only (e.g, if you just want to quickly see who win the game), try:

./minirts-backend replay_cmd --load_replay [your replay]