unet_1d.py

from dataclasses import dataclass
from typing import Optional, Tuple, Union

import torch
import torch.nn as nn

from ..configuration_utils import ConfigMixin, register_to_config
from ..modeling_utils import ModelMixin
from ..utils import BaseOutput
from .embeddings import GaussianFourierProjection, TimestepEmbedding, Timesteps
from .unet_1d_blocks import get_down_block, get_mid_block, get_up_block


@dataclass
class UNet1DOutput(BaseOutput):
    """
    Args:
        sample (`torch.FloatTensor` of shape `(batch_size, num_channels, sample_size)`):
            Hidden states output. Output of last layer of model.
    """

    sample: torch.FloatTensor


class UNet1DModel(ModelMixin, ConfigMixin):
    r"""
    UNet1DModel is a 1D UNet model that takes in a noisy sample and a timestep and returns sample shaped output.

    This model inherits from [`ModelMixin`]. Check the superclass documentation for the generic methods the library
    implements for all the model (such as downloading or saving, etc.)

    Parameters:
        sample_size (`int`, *optionl*): Default length of sample. Should be adaptable at runtime.
        in_channels (`int`, *optional*, defaults to 2): Number of channels in the input sample.
        out_channels (`int`, *optional*, defaults to 2): Number of channels in the output.
        time_embedding_type (`str`, *optional*, defaults to `"fourier"`): Type of time embedding to use.
        freq_shift (`int`, *optional*, defaults to 0): Frequency shift for fourier time embedding.
        flip_sin_to_cos (`bool`, *optional*, defaults to :
            obj:`False`): Whether to flip sin to cos for fourier time embedding.
        down_block_types (`Tuple[str]`, *optional*, defaults to :
            obj:`("DownBlock1D", "DownBlock1DNoSkip", "AttnDownBlock1D")`): Tuple of downsample block types.
        up_block_types (`Tuple[str]`, *optional*, defaults to :
            obj:`("UpBlock1D", "UpBlock1DNoSkip", "AttnUpBlock1D")`): Tuple of upsample block types.
        block_out_channels (`Tuple[int]`, *optional*, defaults to :
            obj:`(32, 32, 64)`): Tuple of block output channels.
    """

    @register_to_config
    def __init__(
        self,
        sample_size: int = 65536,
        sample_rate: Optional[int] = None,
        in_channels: int = 2,
        out_channels: int = 2,
        extra_in_channels: int = 0,
        time_embedding_type: str = "fourier",
        freq_shift: int = 0,
        flip_sin_to_cos: bool = True,
        use_timestep_embedding: bool = False,
        down_block_types: Tuple[str] = ("DownBlock1DNoSkip", "DownBlock1D", "AttnDownBlock1D"),
        mid_block_type: str = "UNetMidBlock1D",
        up_block_types: Tuple[str] = ("AttnUpBlock1D", "UpBlock1D", "UpBlock1DNoSkip"),
        block_out_channels: Tuple[int] = (32, 32, 64),
    ):
        super().__init__()

        self.sample_size = sample_size

        # time
        if time_embedding_type == "fourier":
            self.time_proj = GaussianFourierProjection(
                embedding_size=8, set_W_to_weight=False, log=False, flip_sin_to_cos=flip_sin_to_cos
            )
            timestep_input_dim = 2 * block_out_channels[0]
        elif time_embedding_type == "positional":
            self.time_proj = Timesteps(block_out_channels[0], flip_sin_to_cos, freq_shift)
            timestep_input_dim = block_out_channels[0]

        if use_timestep_embedding:
            time_embed_dim = block_out_channels[0] * 4
            self.time_embedding = TimestepEmbedding(timestep_input_dim, time_embed_dim)

        self.down_blocks = nn.ModuleList([])
        self.mid_block = None
        self.up_blocks = nn.ModuleList([])
        self.out_block = None

        # down
        output_channel = in_channels
        for i, down_block_type in enumerate(down_block_types):
            input_channel = output_channel
            output_channel = block_out_channels[i]

            if i == 0:
                input_channel += extra_in_channels

            down_block = get_down_block(
                down_block_type,
                in_channels=input_channel,
                out_channels=output_channel,
            )
            self.down_blocks.append(down_block)

        # mid
        self.mid_block = get_mid_block(
            mid_block_type=mid_block_type,
            mid_channels=block_out_channels[-1],
            in_channels=block_out_channels[-1],
            out_channels=None,
        )

        # up
        reversed_block_out_channels = list(reversed(block_out_channels))
        output_channel = reversed_block_out_channels[0]
        for i, up_block_type in enumerate(up_block_types):
            prev_output_channel = output_channel
            output_channel = reversed_block_out_channels[i + 1] if i < len(up_block_types) - 1 else out_channels

            up_block = get_up_block(
                up_block_type,
                in_channels=prev_output_channel,
                out_channels=output_channel,
            )
            self.up_blocks.append(up_block)
            prev_output_channel = output_channel

        # TODO(PVP, Nathan) placeholder for RL application to be merged shortly
        # Totally fine to add another layer with a if statement - no need for nn.Identity here

    def forward(
        self,
        sample: torch.FloatTensor,
        timestep: Union[torch.Tensor, float, int],
        return_dict: bool = True,
    ) -> Union[UNet1DOutput, Tuple]:
        r"""
        Args:
            sample (`torch.FloatTensor`): `(batch_size, sample_size, num_channels)` noisy inputs tensor
            timestep (`torch.FloatTensor` or `float` or `int): (batch) timesteps
            return_dict (`bool`, *optional*, defaults to `True`):
                Whether or not to return a [`~models.unet_1d.UNet1DOutput`] instead of a plain tuple.

        Returns:
            [`~models.unet_1d.UNet1DOutput`] or `tuple`: [`~models.unet_1d.UNet1DOutput`] if `return_dict` is True,
            otherwise a `tuple`. When returning a tuple, the first element is the sample tensor.
        """
        # 1. time
        if len(timestep.shape) == 0:
            timestep = timestep[None]

        timestep_embed = self.time_proj(timestep)[..., None]
        timestep_embed = timestep_embed.repeat([1, 1, sample.shape[2]]).to(sample.dtype)

        # 2. down
        down_block_res_samples = ()
        for downsample_block in self.down_blocks:
            sample, res_samples = downsample_block(hidden_states=sample, temb=timestep_embed)
            down_block_res_samples += res_samples

        # 3. mid
        sample = self.mid_block(sample)

        # 4. up
        for i, upsample_block in enumerate(self.up_blocks):
            res_samples = down_block_res_samples[-1:]
            down_block_res_samples = down_block_res_samples[:-1]
            sample = upsample_block(sample, res_samples)

        if not return_dict:
            return (sample,)

        return UNet1DOutput(sample=sample)