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import torch
import torch.nn.functional as F
from einops import rearrange
from torch import nn
class TwoLayerConv2d(nn.Sequential):
def __init__(self, in_channels, out_channels, kernel_size=3):
super().__init__(nn.Conv2d(in_channels, in_channels, kernel_size=kernel_size,
padding=kernel_size // 2, stride=1, bias=False),
nn.BatchNorm2d(in_channels),
nn.ReLU(),
nn.Conv2d(in_channels, out_channels, kernel_size=kernel_size,
padding=kernel_size // 2, stride=1)
)
class Transformer(nn.Module):
def __init__(self, dim, depth, heads, dim_head, mlp_dim, dropout):
super().__init__()
self.layers = nn.ModuleList([])
for _ in range(depth):
self.layers.append(nn.ModuleList([
Residual(PreNorm(dim, Attention(dim, heads = heads, dim_head = dim_head, dropout = dropout))),
Residual(PreNorm(dim, FeedForward(dim, mlp_dim, dropout = dropout)))
]))
def forward(self, x, mask = None):
for attn, ff in self.layers:
x = attn(x, mask = mask)
x = ff(x)
return x
class TransformerDecoder(nn.Module):
def __init__(self, dim, depth, heads, dim_head, mlp_dim, dropout, softmax=True):
super().__init__()
self.layers = nn.ModuleList([])
for _ in range(depth):
self.layers.append(nn.ModuleList([
Residual2(PreNorm2(dim, Cross_Attention(dim, heads = heads,
dim_head = dim_head, dropout = dropout,
softmax=softmax))),
Residual(PreNorm(dim, FeedForward(dim, mlp_dim, dropout = dropout)))
]))
def forward(self, x, m, mask = None):
"""target(query), memory"""
for attn, ff in self.layers:
x = attn(x, m, mask = mask)
x = ff(x)
return x
class PreNorm(nn.Module):
def __init__(self, dim, fn):
super().__init__()
self.norm = nn.LayerNorm(dim)
self.fn = fn
def forward(self, x, **kwargs):
return self.fn(self.norm(x), **kwargs)
class PreNorm2(nn.Module):
def __init__(self, dim, fn):
super().__init__()
self.norm = nn.LayerNorm(dim)
self.fn = fn
def forward(self, x, x2, **kwargs):
return self.fn(self.norm(x), self.norm(x2), **kwargs)
class Residual(nn.Module):
def __init__(self, fn):
super().__init__()
self.fn = fn
def forward(self, x, **kwargs):
return self.fn(x, **kwargs) + x
class Residual2(nn.Module):
def __init__(self, fn):
super().__init__()
self.fn = fn
def forward(self, x, x2, **kwargs):
return self.fn(x, x2, **kwargs) + x
class FeedForward(nn.Module):
def __init__(self, dim, hidden_dim, dropout = 0.):
super().__init__()
self.net = nn.Sequential(
nn.Linear(dim, hidden_dim),
nn.GELU(),
nn.Dropout(dropout),
nn.Linear(hidden_dim, dim),
nn.Dropout(dropout)
)
def forward(self, x):
return self.net(x)
class Attention(nn.Module):
def __init__(self, dim, heads = 8, dim_head = 64, dropout = 0.):
super().__init__()
inner_dim = dim_head * heads
self.heads = heads
self.scale = dim ** -0.5
self.to_qkv = nn.Linear(dim, inner_dim * 3, bias = False)
self.to_out = nn.Sequential(
nn.Linear(inner_dim, dim),
nn.Dropout(dropout)
)
def forward(self, x, mask = None):
b, n, _, h = *x.shape, self.heads
qkv = self.to_qkv(x).chunk(3, dim = -1)
q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> b h n d', h = h), qkv)
dots = torch.einsum('bhid,bhjd->bhij', q, k) * self.scale
mask_value = -torch.finfo(dots.dtype).max
if mask is not None:
mask = F.pad(mask.flatten(1), (1, 0), value = True)
assert mask.shape[-1] == dots.shape[-1], 'mask has incorrect dimensions'
mask = mask[:, None, :] * mask[:, :, None]
dots.masked_fill_(~mask, mask_value)
del mask
attn = dots.softmax(dim=-1)
out = torch.einsum('bhij,bhjd->bhid', attn, v)
out = rearrange(out, 'b h n d -> b n (h d)')
out = self.to_out(out)
return out
class Cross_Attention(nn.Module):
def __init__(self, dim, heads = 8, dim_head = 64, dropout = 0., softmax=True):
super().__init__()
inner_dim = dim_head * heads
self.heads = heads
self.scale = dim ** -0.5
self.softmax = softmax
self.to_q = nn.Linear(dim, inner_dim, bias=False)
self.to_k = nn.Linear(dim, inner_dim, bias=False)
self.to_v = nn.Linear(dim, inner_dim, bias=False)
self.to_out = nn.Sequential(
nn.Linear(inner_dim, dim),
nn.Dropout(dropout)
)
def forward(self, x, m, mask = None):
b, n, _, h = *x.shape, self.heads
q = self.to_q(x)
k = self.to_k(m)
v = self.to_v(m)
q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> b h n d', h = h), [q,k,v])
dots = torch.einsum('bhid,bhjd->bhij', q, k) * self.scale
mask_value = -torch.finfo(dots.dtype).max
if mask is not None:
mask = F.pad(mask.flatten(1), (1, 0), value = True)
assert mask.shape[-1] == dots.shape[-1], 'mask has incorrect dimensions'
mask = mask[:, None, :] * mask[:, :, None]
dots.masked_fill_(~mask, mask_value)
del mask
if self.softmax:
attn = dots.softmax(dim=-1)
else:
attn = dots
# attn = dots
# vis_tmp(dots)
out = torch.einsum('bhij,bhjd->bhid', attn, v)
out = rearrange(out, 'b h n d -> b n (h d)')
out = self.to_out(out)
# vis_tmp2(out)
return out |