Evolutionary Strategies in PyTorch

A set of tools based on evostra for using OpenAI's evolutionary strategies in PyTorch. Keras implementations using evostra will be provided with some examples.

TABLE OF CONTENTS

• Installation
• Usage
• Run

Installation

Your system needs all the prerequisites for the minimal installation of OpenAI gym. These will differ by operating system, so please refer to the gym repository for detailed instructions for your build. You also need to install the PyTorch distribution of your choice. You can trigger CUDA ops by passing in -c or --cuda to the training examples.

Following that:

pip install pytorch_es

Usage

You will find the strategy classes (one as of now) within evolutionary_strategies/strategies. These classes are designed to be used with PyTorch models and take two parameters: a function to get a reward and a list of PyTorch Variables that correspond to parameter layers. This can be achieved in the following manner:

import copy
from functools import partial

from pytorch_es import EvolutionModule


def get_reward(model, weights):
    """
    This function runs your model and generates a reward
    """
    cloned_model = copy.deepcopy(model)
    for i, param in enumerate(cloned_model.parameters()):
        try:
            param.data = weights[i]
        except:
            param.data = weights[i].data

    # run environment and return reward as an integer or float
    return 100


model = generate_pytorch_model()
# EvolutionModule runs the population in a ThreadPool, so
# if you need to inject other arguments, you can do that
# using the partial tool
partial_func = partial(get_reward, model=model)
mother_parameters = list(model.parameters())

es = EvolutionModule(
    mother_parameters, partial_func, population_size=100,
    sigma=0.1, learning_rate=0.001,
    reward_goal=200, consecutive_goal_stopping=20,
    threadcount=10, cuda=cuda, render_test=True
)

• EvolutionModule
  • init
    • parameters (list of PyTorch Variables)
    • reward_function => float (runs episode and returns a reward)
    • population_size=50
    • sigma=0.1
    • learning_rate=0.001
    • decay=1.0
    • sigma_decay=1.0
    • threadcount=4
    • render_test=False
    • cuda=False
    • reward_goal=None
    • consecutive_goal_stopping=None (stops after n tests consecutively return rewards equal-to or greater-than goal)
    • save_path=None (path to save weights at test times)
  • run
    • iterations
    • print_step=10 (frequency with which to run test and save weights)

Run

You can run the examples in the following manner:

python examples/cartpole/train_pytorch.py --weights_path cartpole_weights.p

Examples

Lunar Lander

Solved in 1200~ iterations: population=100, sigma=0.01, learning_rate=0.001.

Cartpole

Solved in 200 iterations: population=10, sigma=0.1, learning_rate=0.001.