processing_action_tokenizer.py

import logging
from typing import ClassVar

import numpy as np
from scipy.fft import dct, idct
from tokenizers import Tokenizer, decoders, pre_tokenizers, processors
from tokenizers.models import BPE
from tokenizers.trainers import BpeTrainer
from transformers import PreTrainedTokenizerFast
from transformers.processing_utils import ProcessorMixin


class UniversalActionProcessor(ProcessorMixin):
    attributes: ClassVar[list[str]] = ["bpe_tokenizer"]
    bpe_tokenizer_class: str = "AutoTokenizer"

    def __init__(
        self,
        bpe_tokenizer: PreTrainedTokenizerFast,
        scale: float = 10,
        vocab_size: int = 1024,
        min_token: int = 0,
        *,
        action_dim: int | None = None,
        time_horizon: int | None = None,
    ):
        self.scale = scale
        self.vocab_size = vocab_size
        self.min_token = min_token

        # Action horizon and dimension needed during decoding. These can be specified
        # in three ways (in order of priority):
        # 1. passed in as kwargs to decode()
        # 2. in the constructor
        # 3. cached from the last time decode() was called
        self.time_horizon = time_horizon
        self.action_dim = action_dim
        self.called_time_horizon = time_horizon
        self.called_action_dim = action_dim

        super().__init__(bpe_tokenizer)

    def __call__(self, action_chunk: np.array) -> np.array:
        assert action_chunk.ndim <= 3, (
            "Only 3 dimensions supported: [batch, timesteps, action_dim]"
        )
        if action_chunk.ndim == 2:
            action_chunk = action_chunk[None, ...]

        # Cache the time horizon and action dimension for decoding
        self.called_time_horizon = action_chunk.shape[-2]
        self.called_action_dim = action_chunk.shape[-1]

        dct_coeff = dct(action_chunk, axis=1, norm="ortho")
        dct_coeff = np.around(dct_coeff * self.scale)
        tokens = []
        for elem in dct_coeff:
            token_str = "".join(
                map(chr, np.maximum(elem.flatten() - self.min_token, 0).astype(int))
            )
            tokens.append(self.bpe_tokenizer(token_str)["input_ids"])
        return tokens

    def decode(
        self,
        tokens: list[list[int]],
        *,
        time_horizon: int | None = None,
        action_dim: int | None = None,
    ) -> np.array:
        self.time_horizon = (
            time_horizon or self.time_horizon or self.called_time_horizon
        )
        self.action_dim = action_dim or self.action_dim or self.called_action_dim

        # Cache the time horizon and action dimension for the next call
        self.called_time_horizon = self.time_horizon
        self.called_action_dim = self.action_dim

        assert self.time_horizon is not None and self.action_dim is not None, (
            "Tokenizer not initialized, call encode() once or pass in time_horizon and action_dim."
        )

        decoded_actions = []
        for token in tokens:
            try:
                decoded_tokens = self.bpe_tokenizer.decode(token)
                decoded_dct_coeff = (
                    np.array(list(map(ord, decoded_tokens))) + self.min_token
                )
                decoded_dct_coeff = decoded_dct_coeff.reshape(-1, self.action_dim)
                assert decoded_dct_coeff.shape == (
                    self.time_horizon,
                    self.action_dim,
                ), (
                    f"Decoded DCT coefficients have shape {decoded_dct_coeff.shape}, expected ({self.time_horizon}, {self.action_dim})"
                )
            except Exception as e:
                print(f"Error decoding tokens: {e}")
                print(f"Tokens: {token}")
                decoded_dct_coeff = np.zeros((self.time_horizon, self.action_dim))
            decoded_actions.append(
                idct(decoded_dct_coeff / self.scale, axis=0, norm="ortho")
            )
        return np.stack(decoded_actions)

    @classmethod
    def fit(
        cls,
        action_data: list[np.array],
        scale: float = 10,
        vocab_size: int = 1024,
        *,
        time_horizon: int | None = None,
        action_dim: int | None = None,
    ) -> "UniversalActionProcessor":
        # Run DCT over all inputs
        dct_tokens = [dct(a, axis=0, norm="ortho").flatten() for a in action_data]

        # Quantize and find min token
        max_token = int(np.around(np.concatenate(dct_tokens) * scale).max())
        min_token = int(np.around(np.concatenate(dct_tokens) * scale).min())
        min_vocab_size = max_token - min_token
        print(
            f"Min token: {min_token}, Max token: {max_token}, Min vocab size: {min_vocab_size}"
        )

        assert min_vocab_size <= vocab_size, (
            f"Vocab size {vocab_size} is too small for the range of tokens {min_vocab_size}"
        )
        if min_vocab_size + 100 > vocab_size:
            logging.warning(
                f"Initial alphabet size {min_vocab_size} is almost as large as the vocab"
                f"size {vocab_size}, consider increasing vocab size"
            )

        assert min_token >= -128 + 10, (
            f"Min token {min_token} is less than -128 + 10 (for buffer space)"
        )
        assert max_token < 128 - 10, (
            f"Max token {max_token} is greater than 128 - 10 (for buffer space)"
        )
        min_token = -128

        # Make token iterator for BPE training
        def _token_iter():
            while dct_tokens:
                tokens = dct_tokens.pop()
                rounded_tokens = np.around(tokens * scale) - min_token
                rounded_tokens = rounded_tokens.astype(int)
                string = "".join(map(chr, rounded_tokens))
                yield string

        # Train BPE tokenizer
        tokenizer = Tokenizer(BPE())
        tokenizer.pre_tokenizer = pre_tokenizers.ByteLevel(
            add_prefix_space=False, use_regex=False
        )
        tokenizer.decoder = decoders.ByteLevel()
        tokenizer.post_processor = processors.ByteLevel(trim_offsets=False)

        # alphabet = [chr(i) for i in range(256)]
        trainer = BpeTrainer(
            vocab_size=vocab_size,
            min_frequency=2,
            show_progress=True,
            special_tokens=[],
            initial_alphabet=pre_tokenizers.ByteLevel.alphabet(),
            # initial_alphabet=alphabet,
            # max_token_length=256,
            max_token_length=10_000,
        )
        tokenizer.train_from_iterator(
            _token_iter(), trainer=trainer, length=len(dct_tokens)
        )

        return cls(
            PreTrainedTokenizerFast(
                tokenizer_object=tokenizer, clean_up_tokenization_spaces=False
            ),
            scale=scale,
            vocab_size=vocab_size,
            min_token=min_token,
            time_horizon=time_horizon,
            action_dim=action_dim,
        )