pyRDDLGym-jax 0.4

pyRDDLGym-jax: automatic differentiation for solving sequential planning problems in JAX.

pyRDDLGym-jax

Author: Mike Gimelfarb

This directory provides:

1. automated translation and compilation of RDDL description files into JAX, converting any RDDL domain to a differentiable simulator!
2. powerful, fast and scalable gradient-based planning algorithms, with extendible and flexible policy class representations, automatic model relaxations for working in discrete and hybrid domains, and much more!

[!NOTE]
While Jax planners can support some discrete state/action problems through model relaxations, on some discrete problems it can perform poorly (though there is an ongoing effort to remedy this!). If you find it is not making sufficient progress, check out the PROST planner (for discrete spaces) or the deep reinforcement learning wrappers.

Contents

• Installation
• Running from the Command Line
• Running from within Python
• Configuring the Planner
• Simulation
• Manual Gradient Calculation
• Citing pyRDDLGym-jax

Installation

To use the compiler or planner without the automated hyper-parameter tuning, you will need the following packages installed:

• pyRDDLGym>=2.0
• tqdm>=4.66
• jax>=0.4.12
• optax>=0.1.9
• dm-haiku>=0.0.10
• tensorflow-probability>=0.21.0

Additionally, if you wish to run the examples, you need rddlrepository>=2. To run the automated tuning optimization, you will also need bayesian-optimization>=1.4.3.

You can install this package, together with all of its requirements, via pip:

pip install rddlrepository pyRDDLGym-jax

Running from the Command Line

A basic run script is provided to run the Jax Planner on any domain in rddlrepository, and can be launched in the command line from the install directory of pyRDDLGym-jax:

python -m pyRDDLGym_jax.examples.run_plan <domain> <instance> <method> <episodes>

where:

• domain is the domain identifier as specified in rddlrepository (i.e. Wildfire_MDP_ippc2014), or a path pointing to a valid domain.rddl file
• instance is the instance identifier (i.e. 1, 2, ... 10), or a path pointing to a valid instance.rddl file
• method is the planning method to use (i.e. drp, slp, replan)
• episodes is the (optional) number of episodes to evaluate the learned policy.

The method parameter supports three possible modes:

• slp is the basic straight line planner described in this paper
• drp is the deep reactive policy network described in this paper
• replan is the same as slp except the plan is recalculated at every decision time step.

A basic run script is also provided to run the automatic hyper-parameter tuning:

python -m pyRDDLGym_jax.examples.run_tune <domain> <instance> <method> <trials> <iters> <workers>

where:

• domain is the domain identifier as specified in rddlrepository (i.e. Wildfire_MDP_ippc2014)
• instance is the instance identifier (i.e. 1, 2, ... 10)
• method is the planning method to use (i.e. drp, slp, replan)
• trials is the (optional) number of trials/episodes to average in evaluating each hyper-parameter setting
• iters is the (optional) maximum number of iterations/evaluations of Bayesian optimization to perform
• workers is the (optional) number of parallel evaluations to be done at each iteration, e.g. the total evaluations = iters * workers.

For example, the following will train the Jax Planner on the Quadcopter domain with 4 drones:

python -m pyRDDLGym_jax.examples.run_plan Quadcopter 1 slp

After several minutes of optimization, you should get a visualization as follows:

Running from within Python

To run the Jax planner from within a Python application, refer to the following example:

import pyRDDLGym
from pyRDDLGym_jax.core.planner import JaxBackpropPlanner, JaxOfflineController

# set up the environment (note the vectorized option must be True)
env = pyRDDLGym.make("domain", "instance", vectorized=True)

# create the planning algorithm
planner = JaxBackpropPlanner(rddl=env.model, **planner_args)
controller = JaxOfflineController(planner, **train_args)

# evaluate the planner
controller.evaluate(env, episodes=1, verbose=True, render=True)
env.close()

Here, we have used the straight-line controller, although you can configure the combination of planner and policy representation if you wish. All controllers are instances of pyRDDLGym's BaseAgent class, so they provide the evaluate() function to streamline interaction with the environment. The **planner_args and **train_args are keyword argument parameters to pass during initialization, but we strongly recommend creating and loading a config file as discussed in the next section.

Configuring the Planner

The simplest way to configure the planner is to write and pass a configuration file with the necessary hyper-parameters. The basic structure of a configuration file is provided below for a straight-line planner:

[Model]
logic='FuzzyLogic'
logic_kwargs={'weight': 20}
tnorm='ProductTNorm'
tnorm_kwargs={}

[Optimizer]
method='JaxStraightLinePlan'
method_kwargs={}
optimizer='rmsprop'
optimizer_kwargs={'learning_rate': 0.001}
batch_size_train=1
batch_size_test=1

[Training]
key=42
epochs=5000
train_seconds=30

The configuration file contains three sections:

• [Model] specifies the fuzzy logic operations used to relax discrete operations to differentiable approximations; the weight dictates the quality of the approximation, and tnorm specifies the type of fuzzy logic for relacing logical operations in RDDL (e.g. ProductTNorm, GodelTNorm, LukasiewiczTNorm)
• [Optimizer] generally specify the optimizer and plan settings; the method specifies the plan/policy representation (e.g. JaxStraightLinePlan, JaxDeepReactivePolicy), the gradient descent settings, learning rate, batch size, etc.
• [Training] specifies computation limits, such as total training time and number of iterations, and options for printing or visualizing information from the planner.

For a policy network approach, simply change the [Optimizer] settings like so:

...
[Optimizer]
method='JaxDeepReactivePolicy'
method_kwargs={'topology': [128, 64], 'activation': 'tanh'}
...

The configuration file must then be passed to the planner during initialization. For example, the previous script here can be modified to set parameters from a config file:

from pyRDDLGym_jax.core.planner import load_config

# load the config file with planner settings
planner_args, _, train_args = load_config("/path/to/config.cfg")
    
# create the planning algorithm
planner = JaxBackpropPlanner(rddl=env.model, **planner_args)
controller = JaxOfflineController(planner, **train_args)
...

Simulation

The JAX compiler can be used as a backend for simulating and evaluating RDDL environments:

import pyRDDLGym
from pyRDDLGym.core.policy import RandomAgent
from pyRDDLGym_jax.core.simulator import JaxRDDLSimulator

# create the environment
env = pyRDDLGym.make("domain", "instance", backend=JaxRDDLSimulator)

# evaluate the random policy
agent = RandomAgent(action_space=env.action_space,
                    num_actions=env.max_allowed_actions)
agent.evaluate(env, verbose=True, render=True)

For some domains, the JAX backend could perform better than the numpy-based one, due to various compiler optimizations. In any event, the simulation results using the JAX backend should (almost) always match the numpy backend.

Manual Gradient Calculation

For custom applications, it is desirable to compute gradients of the model that can be optimized downstream. Fortunately, we provide a very convenient function for compiling the transition/step function P(s, a, s') of the environment into JAX.

import pyRDDLGym
from pyRDDLGym_jax.core.planner import JaxRDDLCompilerWithGrad

# set up the environment
env = pyRDDLGym.make("domain", "instance", vectorized=True)

# create the step function
compiled = JaxRDDLCompilerWithGrad(rddl=env.model)
compiled.compile()
step_fn = compiled.compile_transition()

This will return a JAX compiled (pure) function requiring the following inputs:

• key is the jax.random.PRNGKey key for reproducible randomness
• actions is the dictionary of action fluent tensors
• subs is the dictionary of state-fluent and non-fluent tensors
• model_params are the parameters of the differentiable relaxations, such as weight

The function returns a dictionary containing a variety of variables, such as updated pvariables including next-state fluents (pvar), reward obtained (reward), error codes (error). It is thus possible to apply any JAX transformation to the output of the function, such as computing gradient using jax.grad() or batched simulation using jax.vmap().

Compilation of entire rollouts is also possible by calling the compile_rollouts function. An example is provided to illustrate how you can define your own policy class and compute the return gradient manually.

Citing pyRDDLGym-jax

The following citation describes the main ideas of the framework. Please cite it if you found it useful:

@inproceedings{gimelfarb2024jaxplan,
    title={JaxPlan and GurobiPlan: Optimization Baselines for Replanning in Discrete and Mixed Discrete and Continuous Probabilistic Domains},
    author={Michael Gimelfarb and Ayal Taitler and Scott Sanner},
    booktitle={34th International Conference on Automated Planning and Scheduling},
    year={2024},
    url={https://openreview.net/forum?id=7IKtmUpLEH}
}

The utility optimization is discussed in this paper:

@inproceedings{patton2022distributional,
    title={A distributional framework for risk-sensitive end-to-end planning in continuous mdps},
    author={Patton, Noah and Jeong, Jihwan and Gimelfarb, Mike and Sanner, Scott},
    booktitle={Proceedings of the AAAI Conference on Artificial Intelligence},
    volume={36},
    number={9},
    pages={9894--9901},
    year={2022}
}

Some of the implementation details derive from the following literature, which you may wish to also cite in your research papers:

• Deep reactive policies for planning in stochastic nonlinear domains, AAAI 2019
• Scalable planning with tensorflow for hybrid nonlinear domains, NeurIPS 2017