Unofficial Gato: A Generalist Agent

This repository contains Deepmind's Gato architecture imitation in TensorFlow.

Since Deepmind only mentions parts of the architecture in its paper, We still don't know much about the model.
However, I believe the paper is enough to imitate the architecture, I'm trying to do that with the open source community's help.

Currently, the repository supports the following operations:

Transformer (via GatoTransformer)
Patch Position Encodings (via PatchPositionEncoding)
Embedding Function (via ResidualEmbedding)
Local Observation Position Encodings (via LocalPositionEncoding)
Tokenizing Continuous Values (via ContinuousValueTokenizer)
Shared Embedding (via DiscreteEmbedding)

Action tokens are still a mystery in the paper, I need your help.

However, the repository lacks the following miscellaneous.

Datasets (most important)
Pre-trained tokenizers
Training strategy

But, you can still explore the basic architecture of the Gato based on the paper.

Paper Reviews

Full Episode Sequence

Architecture Variants

Appendix C.1. Transformer Hyperparameters

In the paper, Deepmind tested Gato with 3 architecture variants, 1.18B, 364M, and 79M.
I have named them as large(), baseline() and small() respectively in GatoConfig.

Hyperparameters	Large(1.18B)	Baseline(364M)	Small(79M)
Transformer blocks	24	12	8
Attention heads	16	12	24
Layer width	2048	1536	768
Feedforward hidden size	8192	6144	3072
Key/value size	128	128	32

Residual Embedding

Appendix C.2. Embedding Function

There are no mentions that how many residual networks must be stacked for token embeddings.
Therefore, I remain configurable in GatoConfig.

Whatever how many residual layers are existing, full-preactivation is a key.

The blocks are consisted of:

Version 2 ResNet architecture (based on ResNet50V2)
GroupNorm (instead of LayerNorm)
GeLU (instead of ReLU)

Since the GroupNorm is not supported in TensorFlow, you need to install tensorflow-addons.

Position Encodings

Appendix C.3. Position Encodings

Patch Position Encodings

Like Vision Transformer (ViT) by Google, Gato takes the input images as raster-ordered 16x16 patches.
Unlike the Vision Transformer model, however, Gato divides its patch encoding strategy into 2 phases, training and evaluation.

For high-performance computation in TensorFlow, I have used the following expressions.

$C$ and $R$ mean column and row-wise, and $F$ and $T$ mean from and to respectively.

$$ \begin{align} v^R_F &= \begin{bmatrix} 0 & 32 & 64 & 96 \end{bmatrix} \\ v^R_T &= \begin{bmatrix} 32 & 64 & 96 & 128 \end{bmatrix} \\ v^C_F &= \begin{bmatrix} 0 & 26 & 51 & 77 & 102 \end{bmatrix} \\ v^C_T &= \begin{bmatrix} 26 & 51 & 77 & 102 & 128 \end{bmatrix} \\ \\ P_R &= \begin{cases} \mathsf{if} \ \mathsf{training} & v^R_F + \mathsf{uniform}(v^R_T - v^R_F) \\ \mathsf{otherwise} & \mathsf{round}(\frac{v^R_F + v^R_T}{2}) \end{cases} \\ P_C &= \begin{cases} \mathsf{if} \ \mathsf{training} & v^C_F + \mathsf{uniform}(v^C_T - v^C_F) \\ \mathsf{otherwise} & \mathsf{round}(\frac{v^C_F + v^C_T}{2}) \end{cases} \\ \\ E^R_P &= P_R \cdot 1^{\mathsf{T}}_C \\ E^C_P &= 1^{\mathsf{T}}_R \cdot P_C \\ \\ \therefore E &= E_I + E^R_P + E^C_P \end{align} $$

Local Observation Position Encodings

In the definition of Appendix B., text tokens, image patch tokens, and discrete & continuous values are observation tokens
When Gato receives those values, they must be encoded with their own (local) time steps.

Requirements

pip install tensorflow tensorflow-addons

Contributing

This repository is still a work in progress.
Currently, no downloads and no executables are provided.

I welcome many contributors who can help.

License

Licensed under the MIT license.

mfarisadip / gato