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Transformations

RLDS provides a library of tranformations to efficiently manipulate the datasets of steps and episodes. These transformations use optimizations based on the best practices described in this colab.

See usage examples in the tutorial and in the examples page.

This document only includes an overview of a set of the available functions, see the full documentation of the API in the code.

Batch

  • rlds.transformations.batch: batches a dataset of steps using the tf.data.Dataset window interface (i.e., it allows to batch with overlap). It is particularly useful to generate a dataset of transitions or overlapping trajectories. See an example here.

Construct transitions and trajectories

  • rlds.transformations.pattern_map_from_transform and rlds.transformations.pattern_map: apply Reverb Patterns to an RLDS dataset. If you want to learn more about the patterns, see a tutorial here

Manipulating nested datasets

  • rlds.transformations.episode_length: obtains the lenght of an episode (i.e., a dataset of steps).

  • rlds.transformations.sum_dataset: accumulates the values of a dataset of steps. It can be used to gather the accumulated reward of each episode (example).

  • rlds.transformations.sum_nested_steps: accumulates the required values accross all steps in a dataset of episodes.

  • rlds.transformations.final_step: returns the final step of a dataset of steps.

  • rlds.transformations.map_nested_steps: Applies a transformation to all the steps of a dataset of episodes. The transformation is applied to each step individually.

  • rlds.transformations.apply_nested_steps: Applies a transformation to all the steps dataset of a dataset of episodes. The transformation is applied to each dataset of steps (not to each step separately).

  • rlds.transformations.map_steps: Applies a transformation to all the elements (steps) of a dataset. The transformation is applied to each element individually.

Concatenation

  • rlds.transformations.concatenate: concatenatest two datasets of steps. If the steps contain different fields, the missing fields are added and initialized to zeros.

  • rlds.transformations.concat_if_terminal: concats two datases of steps only if the first one ends ina terminal step. It is used in the examples to add absorbing states to an episode.

Dataset stats

  • rlds.transformations.mean_and_std: calculates the mean and the standard deviation across a dataset of episodes for the given fields. It is used in the examples to apply normalization.

  • rlds.transformations.sar_field_mask: can be used as a parameter to mean_and_std to obtain the mean and standard deviation of the default sar fields (observation, action, reward)

Truncation

  • rlds.transformations.truncate_after_condition: truncates a dataset of steps after the first step that satisfies a condition.

Alignment

  • rlds.transformations.shift_keys: shifts elements of the step. For example, to change from SAR to RSA alignment. It is applied to a steps dataset.

  • rlds.transformations.add_alingment_to_step: adds an extra field to the step indicating what is the alignment.

Zero initialization

  • rlds.transformations.zeros_from_spec: Builds a tensor of zeros with the given spec. If the spec was obtained from a batch of steps where the first dimension is None, it creates a zero step with a batch dimension of 1.

  • rlds.transformations.zero_dataset_like: Creates a dataset of one element with the same spec as the given dataset and initialized to zeros.