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from inspect import isfunction
import math
import torch
import torch.nn.functional as F
from torch import nn
from einops import rearrange
from audioldm.latent_diffusion.util import checkpoint
def exists(val):
return val is not None
def uniq(arr):
return {el: True for el in arr}.keys()
def default(val, d):
if exists(val):
return val
return d() if isfunction(d) else d
def max_neg_value(t):
return -torch.finfo(t.dtype).max
def init_(tensor):
dim = tensor.shape[-1]
std = 1 / math.sqrt(dim)
tensor.uniform_(-std, std)
return tensor
# feedforward
class GEGLU(nn.Module):
def __init__(self, dim_in, dim_out):
super().__init__()
self.proj = nn.Linear(dim_in, dim_out * 2)
def forward(self, x):
x, gate = self.proj(x).chunk(2, dim=-1)
return x * F.gelu(gate)
class FeedForward(nn.Module):
def __init__(self, dim, dim_out=None, mult=4, glu=False, dropout=0.0):
super().__init__()
inner_dim = int(dim * mult)
dim_out = default(dim_out, dim)
project_in = (
nn.Sequential(nn.Linear(dim, inner_dim), nn.GELU())
if not glu
else GEGLU(dim, inner_dim)
)
self.net = nn.Sequential(
project_in, nn.Dropout(dropout), nn.Linear(inner_dim, dim_out)
)
def forward(self, x):
return self.net(x)
def zero_module(module):
"""
Zero out the parameters of a module and return it.
"""
for p in module.parameters():
p.detach().zero_()
return module
def Normalize(in_channels):
return torch.nn.GroupNorm(
num_groups=32, num_channels=in_channels, eps=1e-6, affine=True
)
class LinearAttention(nn.Module):
def __init__(self, dim, heads=4, dim_head=32):
super().__init__()
self.heads = heads
hidden_dim = dim_head * heads
self.to_qkv = nn.Conv2d(dim, hidden_dim * 3, 1, bias=False)
self.to_out = nn.Conv2d(hidden_dim, dim, 1)
def forward(self, x):
b, c, h, w = x.shape
qkv = self.to_qkv(x)
q, k, v = rearrange(
qkv, "b (qkv heads c) h w -> qkv b heads c (h w)", heads=self.heads, qkv=3
)
k = k.softmax(dim=-1)
context = torch.einsum("bhdn,bhen->bhde", k, v)
out = torch.einsum("bhde,bhdn->bhen", context, q)
out = rearrange(
out, "b heads c (h w) -> b (heads c) h w", heads=self.heads, h=h, w=w
)
return self.to_out(out)
class SpatialSelfAttention(nn.Module):
def __init__(self, in_channels):
super().__init__()
self.in_channels = in_channels
self.norm = Normalize(in_channels)
self.q = torch.nn.Conv2d(
in_channels, in_channels, kernel_size=1, stride=1, padding=0
)
self.k = torch.nn.Conv2d(
in_channels, in_channels, kernel_size=1, stride=1, padding=0
)
self.v = torch.nn.Conv2d(
in_channels, in_channels, kernel_size=1, stride=1, padding=0
)
self.proj_out = torch.nn.Conv2d(
in_channels, in_channels, kernel_size=1, stride=1, padding=0
)
def forward(self, x):
h_ = x
h_ = self.norm(h_)
q = self.q(h_)
k = self.k(h_)
v = self.v(h_)
# compute attention
b, c, h, w = q.shape
q = rearrange(q, "b c h w -> b (h w) c")
k = rearrange(k, "b c h w -> b c (h w)")
w_ = torch.einsum("bij,bjk->bik", q, k)
w_ = w_ * (int(c) ** (-0.5))
w_ = torch.nn.functional.softmax(w_, dim=2)
# attend to values
v = rearrange(v, "b c h w -> b c (h w)")
w_ = rearrange(w_, "b i j -> b j i")
h_ = torch.einsum("bij,bjk->bik", v, w_)
h_ = rearrange(h_, "b c (h w) -> b c h w", h=h)
h_ = self.proj_out(h_)
return x + h_
class CrossAttention(nn.Module):
"""
### Cross Attention Layer
This falls-back to self-attention when conditional embeddings are not specified.
"""
# use_flash_attention: bool = True
use_flash_attention: bool = False
def __init__(
self,
query_dim,
context_dim=None,
heads=8,
dim_head=64,
dropout=0.0,
is_inplace: bool = True,
):
# def __init__(self, d_model: int, d_cond: int, n_heads: int, d_head: int, is_inplace: bool = True):
"""
:param d_model: is the input embedding size
:param n_heads: is the number of attention heads
:param d_head: is the size of a attention head
:param d_cond: is the size of the conditional embeddings
:param is_inplace: specifies whether to perform the attention softmax computation inplace to
save memory
"""
super().__init__()
self.is_inplace = is_inplace
self.n_heads = heads
self.d_head = dim_head
# Attention scaling factor
self.scale = dim_head**-0.5
# The normal self-attention layer
if context_dim is None:
context_dim = query_dim
# Query, key and value mappings
d_attn = dim_head * heads
self.to_q = nn.Linear(query_dim, d_attn, bias=False)
self.to_k = nn.Linear(context_dim, d_attn, bias=False)
self.to_v = nn.Linear(context_dim, d_attn, bias=False)
# Final linear layer
self.to_out = nn.Sequential(nn.Linear(d_attn, query_dim), nn.Dropout(dropout))
# Setup [flash attention](https://github.com/HazyResearch/flash-attention).
# Flash attention is only used if it's installed
# and `CrossAttention.use_flash_attention` is set to `True`.
try:
# You can install flash attention by cloning their Github repo,
# [https://github.com/HazyResearch/flash-attention](https://github.com/HazyResearch/flash-attention)
# and then running `python setup.py install`
from flash_attn.flash_attention import FlashAttention
self.flash = FlashAttention()
# Set the scale for scaled dot-product attention.
self.flash.softmax_scale = self.scale
# Set to `None` if it's not installed
except ImportError:
self.flash = None
def forward(self, x, context=None, mask=None):
"""
:param x: are the input embeddings of shape `[batch_size, height * width, d_model]`
:param cond: is the conditional embeddings of shape `[batch_size, n_cond, d_cond]`
"""
# If `cond` is `None` we perform self attention
has_cond = context is not None
if not has_cond:
context = x
# Get query, key and value vectors
q = self.to_q(x)
k = self.to_k(context)
v = self.to_v(context)
# Use flash attention if it's available and the head size is less than or equal to `128`
if (
CrossAttention.use_flash_attention
and self.flash is not None
and not has_cond
and self.d_head <= 128
):
return self.flash_attention(q, k, v)
# Otherwise, fallback to normal attention
else:
return self.normal_attention(q, k, v)
def flash_attention(self, q: torch.Tensor, k: torch.Tensor, v: torch.Tensor):
"""
#### Flash Attention
:param q: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
:param k: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
:param v: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
"""
# Get batch size and number of elements along sequence axis (`width * height`)
batch_size, seq_len, _ = q.shape
# Stack `q`, `k`, `v` vectors for flash attention, to get a single tensor of
# shape `[batch_size, seq_len, 3, n_heads * d_head]`
qkv = torch.stack((q, k, v), dim=2)
# Split the heads
qkv = qkv.view(batch_size, seq_len, 3, self.n_heads, self.d_head)
# Flash attention works for head sizes `32`, `64` and `128`, so we have to pad the heads to
# fit this size.
if self.d_head <= 32:
pad = 32 - self.d_head
elif self.d_head <= 64:
pad = 64 - self.d_head
elif self.d_head <= 128:
pad = 128 - self.d_head
else:
raise ValueError(f"Head size ${self.d_head} too large for Flash Attention")
# Pad the heads
if pad:
qkv = torch.cat(
(qkv, qkv.new_zeros(batch_size, seq_len, 3, self.n_heads, pad)), dim=-1
)
# Compute attention
# $$\underset{seq}{softmax}\Bigg(\frac{Q K^\top}{\sqrt{d_{key}}}\Bigg)V$$
# This gives a tensor of shape `[batch_size, seq_len, n_heads, d_padded]`
# TODO here I add the dtype changing
out, _ = self.flash(qkv.type(torch.float16))
# Truncate the extra head size
out = out[:, :, :, : self.d_head].float()
# Reshape to `[batch_size, seq_len, n_heads * d_head]`
out = out.reshape(batch_size, seq_len, self.n_heads * self.d_head)
# Map to `[batch_size, height * width, d_model]` with a linear layer
return self.to_out(out)
def normal_attention(self, q: torch.Tensor, k: torch.Tensor, v: torch.Tensor):
"""
#### Normal Attention
:param q: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
:param k: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
:param v: are the query vectors before splitting heads, of shape `[batch_size, seq, d_attn]`
"""
# Split them to heads of shape `[batch_size, seq_len, n_heads, d_head]`
q = q.view(*q.shape[:2], self.n_heads, -1) # [bs, 64, 20, 32]
k = k.view(*k.shape[:2], self.n_heads, -1) # [bs, 1, 20, 32]
v = v.view(*v.shape[:2], self.n_heads, -1)
# Calculate attention $\frac{Q K^\top}{\sqrt{d_{key}}}$
attn = torch.einsum("bihd,bjhd->bhij", q, k) * self.scale
# Compute softmax
# $$\underset{seq}{softmax}\Bigg(\frac{Q K^\top}{\sqrt{d_{key}}}\Bigg)$$
if self.is_inplace:
half = attn.shape[0] // 2
attn[half:] = attn[half:].softmax(dim=-1)
attn[:half] = attn[:half].softmax(dim=-1)
else:
attn = attn.softmax(dim=-1)
# Compute attention output
# $$\underset{seq}{softmax}\Bigg(\frac{Q K^\top}{\sqrt{d_{key}}}\Bigg)V$$
# attn: [bs, 20, 64, 1]
# v: [bs, 1, 20, 32]
out = torch.einsum("bhij,bjhd->bihd", attn, v)
# Reshape to `[batch_size, height * width, n_heads * d_head]`
out = out.reshape(*out.shape[:2], -1)
# Map to `[batch_size, height * width, d_model]` with a linear layer
return self.to_out(out)
# class CrossAttention(nn.Module):
# def __init__(self, query_dim, context_dim=None, heads=8, dim_head=64, dropout=0.):
# super().__init__()
# inner_dim = dim_head * heads
# context_dim = default(context_dim, query_dim)
# self.scale = dim_head ** -0.5
# self.heads = heads
# self.to_q = nn.Linear(query_dim, inner_dim, bias=False)
# self.to_k = nn.Linear(context_dim, inner_dim, bias=False)
# self.to_v = nn.Linear(context_dim, inner_dim, bias=False)
# self.to_out = nn.Sequential(
# nn.Linear(inner_dim, query_dim),
# nn.Dropout(dropout)
# )
# def forward(self, x, context=None, mask=None):
# h = self.heads
# q = self.to_q(x)
# context = default(context, x)
# k = self.to_k(context)
# v = self.to_v(context)
# q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> (b h) n d', h=h), (q, k, v))
# sim = einsum('b i d, b j d -> b i j', q, k) * self.scale
# if exists(mask):
# mask = rearrange(mask, 'b ... -> b (...)')
# max_neg_value = -torch.finfo(sim.dtype).max
# mask = repeat(mask, 'b j -> (b h) () j', h=h)
# sim.masked_fill_(~mask, max_neg_value)
# # attention, what we cannot get enough of
# attn = sim.softmax(dim=-1)
# out = einsum('b i j, b j d -> b i d', attn, v)
# out = rearrange(out, '(b h) n d -> b n (h d)', h=h)
# return self.to_out(out)
class BasicTransformerBlock(nn.Module):
def __init__(
self,
dim,
n_heads,
d_head,
dropout=0.0,
context_dim=None,
gated_ff=True,
checkpoint=True,
):
super().__init__()
self.attn1 = CrossAttention(
query_dim=dim, heads=n_heads, dim_head=d_head, dropout=dropout
) # is a self-attention
self.ff = FeedForward(dim, dropout=dropout, glu=gated_ff)
self.attn2 = CrossAttention(
query_dim=dim,
context_dim=context_dim,
heads=n_heads,
dim_head=d_head,
dropout=dropout,
) # is self-attn if context is none
self.norm1 = nn.LayerNorm(dim)
self.norm2 = nn.LayerNorm(dim)
self.norm3 = nn.LayerNorm(dim)
self.checkpoint = checkpoint
def forward(self, x, context=None):
if context is None:
return checkpoint(self._forward, (x,), self.parameters(), self.checkpoint)
else:
return checkpoint(
self._forward, (x, context), self.parameters(), self.checkpoint
)
def _forward(self, x, context=None):
x = self.attn1(self.norm1(x)) + x
x = self.attn2(self.norm2(x), context=context) + x
x = self.ff(self.norm3(x)) + x
return x
class SpatialTransformer(nn.Module):
"""
Transformer block for image-like data.
First, project the input (aka embedding)
and reshape to b, t, d.
Then apply standard transformer action.
Finally, reshape to image
"""
def __init__(
self,
in_channels,
n_heads,
d_head,
depth=1,
dropout=0.0,
context_dim=None,
no_context=False,
):
super().__init__()
if no_context:
context_dim = None
self.in_channels = in_channels
inner_dim = n_heads * d_head
self.norm = Normalize(in_channels)
self.proj_in = nn.Conv2d(
in_channels, inner_dim, kernel_size=1, stride=1, padding=0
)
self.transformer_blocks = nn.ModuleList(
[
BasicTransformerBlock(
inner_dim, n_heads, d_head, dropout=dropout, context_dim=context_dim
)
for d in range(depth)
]
)
self.proj_out = zero_module(
nn.Conv2d(inner_dim, in_channels, kernel_size=1, stride=1, padding=0)
)
def forward(self, x, context=None):
# note: if no context is given, cross-attention defaults to self-attention
b, c, h, w = x.shape
x_in = x
x = self.norm(x)
x = self.proj_in(x)
x = rearrange(x, "b c h w -> b (h w) c")
for block in self.transformer_blocks:
x = block(x, context=context)
x = rearrange(x, "b (h w) c -> b c h w", h=h, w=w)
x = self.proj_out(x)
return x + x_in