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Description:

rl8 0.2.0

rl8 is a minimal end-to-end RL library that can simulate highly
parallelized, infinite horizon environments, and can train a PPO policy
using those environments, achieving up to 1M environment transitions
(and one policy update) per second using a single NVIDIA RTX 2080.

Documentation: https://theogognf.github.io/rl8/
PyPI: https://pypi.org/project/rl8/
Repository: https://github.com/theOGognf/rl8

The figure below depicts rl8’s experiment tracking integration with
MLflow and rl8’s ability to solve reinforcement learning problems
within seconds.

Quick Start

Installation
Install with pip for the latest (stable) version.
pip install rl8
Install from GitHub for the latest (unstable) version.
git clone https://github.com/theOGognf/rl8.git
pip install ./rl8/

Basic Usage
Train a policy with PPO and log training progress with MLflow using the
high-level trainer interface (this updates the policy indefinitely).
from rl8 import Trainer
from rl8.env import DiscreteDummyEnv

trainer = Trainer(DiscreteDummyEnv)
trainer.run()
Collect environment transitions and update a policy directly using the
low-level algorithm interface (this updates the policy once).
from rl8 import Algorithm
from rl8.env import DiscreteDummyEnv

algo = Algorithm(DiscreteDummyEnv)
algo.collect()
algo.step()
The trainer interface is the most popular interface for policy training
workflows, whereas the algorithm interface is useful for lower-level
customization of policy training workflows.

Concepts
rl8 is minimal in that it limits the number of interfaces required for
training a policy with PPO without restrictions on observation and action
specs, custom models, and custom action distributions.
rl8 is built around six key concepts:

The environment: The simulation that the policy learns to interact with.
The model: The policy parameterization that determines how the policy
processes environment observations and how parameters for the action
distribution are generated.
The action distribution: The mechanism for representing actions
conditioned on environment observations and model outputs. Environment
actions are ultimately sampled from the action distribution.
The policy: The union of the model and the action distribution that
actually calls and samples from the model and action distribution,
respectively.
The algorithm: The PPO implementation that uses the environment to train
the policy (i.e., update the model’s parameters).
The trainer: The high-level interface for using the algorithm to train
indefinitely or until some condition is met. The trainer directly integrates
with MLflow to track experiments and training progress.

Quick Examples
These short snippets showcase rl8’s main features. See the examples
for complete implementations of rl8-compatible environments and models.

Customizing Training Runs
Use a custom distribution and custom hyperparameters by passing
options to the trainer (or algorithm) interface.
from rl8 import SquashedNormal, Trainer
from rl8.env import ContinuousDummyEnv

trainer = Trainer(
ContinuousDummyEnv,
distribution_cls=SquashedNormal,
gae_lambda=0.99,
gamma=0.99,
)
trainer.run()

Training a Recurrent Policy
Swap to the recurrent flavor of the trainer (or algorithm) interface
to train a recurrent model and policy.
from rl8 import RecurrentTrainer
from rl8.env import DiscreteDummyEnv

trainer = RecurrentTrainer(DiscreteDummyEnv)
trainer.run()

Training on a GPU
Specify the device used across the environment, model, and
algorithm.
from rl8 import Trainer
from rl8.env import DiscreteDummyEnv

trainer = Trainer(DiscreteDummyEnv, device="cuda")
trainer.run()

Minimizing GPU Memory Usage
Enable policy updates with gradient accumulation and/or
Automatic Mixed Precision (AMP) to minimize GPU memory
usage so you can simulate more environments or use larger models.
import torch.optim as optim

from rl8 import Trainer
from rl8.env import DiscreteDummyEnv

trainer = Trainer(
DiscreteDummyEnv,
optimizer_cls=optim.SGD,
accumulate_grads=True,
enable_amp=True,
sgd_minibatch_size=8192,
device="cuda",
)
trainer.run()

Specifying Training Stop Conditions
Specify conditions based on training statistics to stop training early.
from rl8 import Trainer
from rl8.conditions import Plateaus
from rl8.env import DiscreteDummyEnv

trainer = Trainer(DiscreteDummyEnv)
trainer.run(stop_conditions=[Plateaus("returns/mean", rtol=0.05)])

Why rl8?
TL;DR: rl8 focuses on a niche subset of RL that simplifies the overall
library while allowing fast and fully customizable environments, models, and
action distributions.
There are many high quality, open-sourced RL libraries. Most of them take on the
daunting task of being a monolithic, one-stop-shop for everything RL, attempting to
support as many algorithms, environments, models, and compute capabilities as possible.
Naturely, this monolothic goal has some drawbacks:

The software becomes more dense with each supported feature, making the library
all-the-more difficult to customize for a specific use case.
The software becomes less performant for a specific use case. RL practitioners
typically end up accepting the cost of transitioning to expensive and
difficult-to-manage compute clusters to get results faster.

Rather than focusing on being a monolithic RL library, rl8 fills the niche
of maximizing training performance for a few key assumptions:

Environments are highly parallelized and their parallelization is entirely
managed within the environment. This allows rl8 to ignore distributed
computing design considerations.
Environments are infinite horizon (i.e., they have no terminal conditions).
This allows rl8 to reset environments at the same, fixed horizon
intervals, greatly simplifying environment and algorithm implementations.
The only supported ML framework is PyTorch and the only supported algorithm
is PPO. This allows rl8 to ignore layers upon layers of abstraction,
greatly simplifying the overall library implementation.

The end result is a minimal and high throughput library that can train policies
to solve complex tasks within minutes on consumer grade compute devices.
Unfortunately, this means rl8 doesn’t support as many use cases as
a monolithic RL library might. In fact, rl8 is probably a bad fit for
your use case if:

Your environment isn’t parallelizable.
Your environment must contain terminal conditions and can’t be reformulated
as an infinite horizon task.
You want to use an ML framework that isn’t PyTorch or you want to use an
algorithm that isn’t a variant of PPO.

However, if rl8 does fit your use case, it can do wonders for your
RL workflow.

Related Projects

RL Games: RL Games is a high performance RL library built around popular
environment protocols.
RLlib: Ray’s RLlib is the industry standard RL library that supports many
popular RL algorithms. RLlib can scale RL workloads from your laptop all the
way to the cloud with little-to-no changes to your code.
Sample Factory: Sample Factory provides an efficient and high quality
implementation of PPO with a focus on accelerating training for a single machine
with support for a wide variety of environment protocols.
SKRL: SKRL focuses on readability, simplicity, and transparency of RL algorithm
implementations with support for a wide variety of environment protocols.
Stable Baselines 3: Stable Baselines 3 is a set of reliable and user-friendly
RL algorithm implementations that integrate with a rich set of features desirable
by most practitioners and use cases.
TorchRL: TorchRL is PyTorch’s RL library that’s focused on efficient, modular,
documented, and tested RL building blocks and algorithm implementations aimed
at supporting research in RL. TorchRL is a direct dependency of rl8.