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from dataclasses import dataclass
from typing import Optional
import torch
from torch import nn
from spar3d.models.transformers.attention import BasicTransformerBlock
from spar3d.models.utils import BaseModule
class Transformer1D(BaseModule):
"""
A 1D Transformer model for sequence data.
Parameters:
num_attention_heads (`int`, *optional*, defaults to 16): The number of heads to use for multi-head attention.
attention_head_dim (`int`, *optional*, defaults to 88): The number of channels in each head.
in_channels (`int`, *optional*):
The number of channels in the input and output (specify if the input is **continuous**).
num_layers (`int`, *optional*, defaults to 1): The number of layers of Transformer blocks to use.
cross_attention_dim (`int`, *optional*): The number of `encoder_hidden_states` dimensions to use.
activation_fn (`str`, *optional*, defaults to `"geglu"`): Activation function to use in feed-forward.
attention_bias (`bool`, *optional*):
Configure if the `TransformerBlocks` attention should contain a bias parameter.
"""
@dataclass
class Config(BaseModule.Config):
num_attention_heads: int = 16
attention_head_dim: int = 88
in_channels: Optional[int] = None
out_channels: Optional[int] = None
num_layers: int = 1
norm_num_groups: int = 32
attention_bias: bool = False
activation_fn: str = "geglu"
norm_elementwise_affine: bool = True
residual: bool = True
input_layer_norm: bool = True
norm_eps: float = 1e-5
cfg: Config
def configure(self) -> None:
self.num_attention_heads = self.cfg.num_attention_heads
self.attention_head_dim = self.cfg.attention_head_dim
inner_dim = self.num_attention_heads * self.attention_head_dim
linear_cls = nn.Linear
# 2. Define input layers
self.in_channels = self.cfg.in_channels
self.norm = torch.nn.GroupNorm(
num_groups=self.cfg.norm_num_groups,
num_channels=self.cfg.in_channels,
eps=self.cfg.norm_eps,
affine=True,
)
self.proj_in = linear_cls(self.cfg.in_channels, inner_dim)
# 3. Define transformers blocks
self.transformer_blocks = nn.ModuleList(
[
BasicTransformerBlock(
inner_dim,
self.num_attention_heads,
self.attention_head_dim,
activation_fn=self.cfg.activation_fn,
attention_bias=self.cfg.attention_bias,
norm_elementwise_affine=self.cfg.norm_elementwise_affine,
norm_eps=self.cfg.norm_eps,
)
for d in range(self.cfg.num_layers)
]
)
# 4. Define output layers
self.out_channels = (
self.cfg.in_channels
if self.cfg.out_channels is None
else self.cfg.out_channels
)
self.proj_out = linear_cls(inner_dim, self.cfg.in_channels)
def forward(
self,
hidden_states: torch.Tensor,
attention_mask: Optional[torch.Tensor] = None,
encoder_attention_mask: Optional[torch.Tensor] = None,
):
"""
The [`Transformer1DModel`] forward method.
Args:
hidden_states (`torch.LongTensor` of shape `(batch size, num latent pixels)` if discrete, `torch.FloatTensor` of shape `(batch size, channel, height, width)` if continuous):
Input `hidden_states`.
encoder_hidden_states ( `torch.FloatTensor` of shape `(batch size, sequence len, embed dims)`, *optional*):
Conditional embeddings for cross attention layer. If not given, cross-attention defaults to
self-attention.
attention_mask ( `torch.Tensor`, *optional*):
An attention mask of shape `(batch, key_tokens)` is applied to `encoder_hidden_states`. If `1` the mask
is kept, otherwise if `0` it is discarded. Mask will be converted into a bias, which adds large
negative values to the attention scores corresponding to "discard" tokens.
encoder_attention_mask ( `torch.Tensor`, *optional*):
Cross-attention mask applied to `encoder_hidden_states`. Two formats supported:
* Mask `(batch, sequence_length)` True = keep, False = discard.
* Bias `(batch, 1, sequence_length)` 0 = keep, -10000 = discard.
If `ndim == 2`: will be interpreted as a mask, then converted into a bias consistent with the format
above. This bias will be added to the cross-attention scores.
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~models.unet_2d_condition.UNet2DConditionOutput`] instead of a plain
tuple.
Returns:
If `return_dict` is True, an [`~models.transformer_2d.Transformer2DModelOutput`] is returned, otherwise a
`tuple` where the first element is the sample tensor.
"""
# ensure attention_mask is a bias, and give it a singleton query_tokens dimension.
# we may have done this conversion already, e.g. if we came here via UNet2DConditionModel#forward.
# we can tell by counting dims; if ndim == 2: it's a mask rather than a bias.
# expects mask of shape:
# [batch, key_tokens]
# adds singleton query_tokens dimension:
# [batch, 1, key_tokens]
# this helps to broadcast it as a bias over attention scores, which will be in one of the following shapes:
# [batch, heads, query_tokens, key_tokens] (e.g. torch sdp attn)
# [batch * heads, query_tokens, key_tokens] (e.g. xformers or classic attn)
if attention_mask is not None and attention_mask.ndim == 2:
# assume that mask is expressed as:
# (1 = keep, 0 = discard)
# convert mask into a bias that can be added to attention scores:
# (keep = +0, discard = -10000.0)
attention_mask = (1 - attention_mask.to(hidden_states.dtype)) * -10000.0
attention_mask = attention_mask.unsqueeze(1)
# convert encoder_attention_mask to a bias the same way we do for attention_mask
if encoder_attention_mask is not None and encoder_attention_mask.ndim == 2:
encoder_attention_mask = (
1 - encoder_attention_mask.to(hidden_states.dtype)
) * -10000.0
encoder_attention_mask = encoder_attention_mask.unsqueeze(1)
# 1. Input
batch, _, seq_len = hidden_states.shape
residual = hidden_states
if self.cfg.input_layer_norm:
hidden_states = self.norm(hidden_states)
inner_dim = hidden_states.shape[1]
hidden_states = hidden_states.permute(0, 2, 1).reshape(
batch, seq_len, inner_dim
)
hidden_states = self.proj_in(hidden_states)
# 2. Blocks
for block in self.transformer_blocks:
hidden_states = block(
hidden_states,
attention_mask=attention_mask,
)
# 3. Output
hidden_states = self.proj_out(hidden_states)
hidden_states = (
hidden_states.reshape(batch, seq_len, inner_dim)
.permute(0, 2, 1)
.contiguous()
)
if self.cfg.residual:
output = hidden_states + residual
else:
output = hidden_states
return output
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