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from collections import OrderedDict
import math
from typing import Callable, Optional, Sequence, Tuple
import torch
from torch import nn
from torch.nn import functional as F
from torch.utils.checkpoint import checkpoint
class LayerNormFp32(nn.LayerNorm):
"""Subclass torch's LayerNorm to handle fp16 (by casting to float32 and back)."""
def forward(self, x: torch.Tensor):
orig_type = x.dtype
x = F.layer_norm(x.to(torch.float32), self.normalized_shape, self.weight, self.bias, self.eps)
return x.to(orig_type)
class LayerNorm(nn.LayerNorm):
"""Subclass torch's LayerNorm (with cast back to input dtype)."""
def forward(self, x: torch.Tensor):
orig_type = x.dtype
x = F.layer_norm(x, self.normalized_shape, self.weight, self.bias, self.eps)
return x.to(orig_type)
class QuickGELU(nn.Module):
# NOTE This is slower than nn.GELU or nn.SiLU and uses more GPU memory
def forward(self, x: torch.Tensor):
return x * torch.sigmoid(1.702 * x)
class LayerScale(nn.Module):
def __init__(self, dim, init_values=1e-5, inplace=False):
super().__init__()
self.inplace = inplace
self.gamma = nn.Parameter(init_values * torch.ones(dim))
def forward(self, x):
return x.mul_(self.gamma) if self.inplace else x * self.gamma
class PatchDropout(nn.Module):
"""
https://arxiv.org/abs/2212.00794
"""
def __init__(self, prob, exclude_first_token=True):
super().__init__()
assert 0 <= prob < 1.
self.prob = prob
self.exclude_first_token = exclude_first_token # exclude CLS token
def forward(self, x):
if not self.training or self.prob == 0.:
return x
if self.exclude_first_token:
cls_tokens, x = x[:, :1], x[:, 1:]
else:
cls_tokens = torch.jit.annotate(torch.Tensor, x[:, :1])
batch = x.size()[0]
num_tokens = x.size()[1]
batch_indices = torch.arange(batch)
batch_indices = batch_indices[..., None]
keep_prob = 1 - self.prob
num_patches_keep = max(1, int(num_tokens * keep_prob))
rand = torch.randn(batch, num_tokens)
patch_indices_keep = rand.topk(num_patches_keep, dim=-1).indices
x = x[batch_indices, patch_indices_keep]
if self.exclude_first_token:
x = torch.cat((cls_tokens, x), dim=1)
return x
class Attention(nn.Module):
def __init__(
self,
dim,
num_heads=8,
qkv_bias=True,
scaled_cosine=False,
scale_heads=False,
logit_scale_max=math.log(1. / 0.01),
attn_drop=0.,
proj_drop=0.
):
super().__init__()
self.scaled_cosine = scaled_cosine
self.scale_heads = scale_heads
assert dim % num_heads == 0, 'dim should be divisible by num_heads'
self.num_heads = num_heads
self.head_dim = dim // num_heads
self.scale = self.head_dim ** -0.5
self.logit_scale_max = logit_scale_max
# keeping in_proj in this form (instead of nn.Linear) to match weight scheme of original
self.in_proj_weight = nn.Parameter(torch.randn((dim * 3, dim)) * self.scale)
if qkv_bias:
self.in_proj_bias = nn.Parameter(torch.zeros(dim * 3))
else:
self.in_proj_bias = None
if self.scaled_cosine:
self.logit_scale = nn.Parameter(torch.log(10 * torch.ones((num_heads, 1, 1))))
else:
self.logit_scale = None
self.attn_drop = nn.Dropout(attn_drop)
if self.scale_heads:
self.head_scale = nn.Parameter(torch.ones((num_heads, 1, 1)))
else:
self.head_scale = None
self.out_proj = nn.Linear(dim, dim)
self.out_drop = nn.Dropout(proj_drop)
def forward(self, x, attn_mask: Optional[torch.Tensor] = None):
L, N, C = x.shape
q, k, v = F.linear(x, self.in_proj_weight, self.in_proj_bias).chunk(3, dim=-1)
q = q.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)
k = k.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)
v = v.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)
if self.logit_scale is not None:
attn = torch.bmm(F.normalize(q, dim=-1), F.normalize(k, dim=-1).transpose(-1, -2))
logit_scale = torch.clamp(self.logit_scale, max=self.logit_scale_max).exp()
attn = attn.view(N, self.num_heads, L, L) * logit_scale
attn = attn.view(-1, L, L)
else:
q = q * self.scale
attn = torch.bmm(q, k.transpose(-1, -2))
if attn_mask is not None:
if attn_mask.dtype == torch.bool:
new_attn_mask = torch.zeros_like(attn_mask, dtype=q.dtype)
new_attn_mask.masked_fill_(attn_mask, float("-inf"))
attn_mask = new_attn_mask
attn += attn_mask
attn = attn.softmax(dim=-1)
attn = self.attn_drop(attn)
x = torch.bmm(attn, v)
if self.head_scale is not None:
x = x.view(N, self.num_heads, L, C) * self.head_scale
x = x.view(-1, L, C)
x = x.transpose(0, 1).reshape(L, N, C)
x = self.out_proj(x)
x = self.out_drop(x)
return x
class ResidualAttentionBlock(nn.Module):
def __init__(
self,
d_model: int,
n_head: int,
mlp_ratio: float = 4.0,
ls_init_value: float = None,
act_layer: Callable = nn.GELU,
norm_layer: Callable = LayerNorm,
is_cross_attention: bool = False,
):
super().__init__()
self.ln_1 = norm_layer(d_model)
self.attn = nn.MultiheadAttention(d_model, n_head)
self.ls_1 = LayerScale(d_model, ls_init_value) if ls_init_value is not None else nn.Identity()
if is_cross_attention:
self.ln_1_kv = norm_layer(d_model)
self.ln_2 = norm_layer(d_model)
mlp_width = int(d_model * mlp_ratio)
self.mlp = nn.Sequential(OrderedDict([
("c_fc", nn.Linear(d_model, mlp_width)),
("gelu", act_layer()),
("c_proj", nn.Linear(mlp_width, d_model))
]))
self.ls_2 = LayerScale(d_model, ls_init_value) if ls_init_value is not None else nn.Identity()
def attention(
self,
q_x: torch.Tensor,
k_x: Optional[torch.Tensor] = None,
v_x: Optional[torch.Tensor] = None,
attn_mask: Optional[torch.Tensor] = None,
):
k_x = k_x if k_x is not None else q_x
v_x = v_x if v_x is not None else q_x
attn_mask = attn_mask.to(q_x.dtype) if attn_mask is not None else None
return self.attn(
q_x, k_x, v_x, need_weights=False, attn_mask=attn_mask
)[0]
def forward(
self,
q_x: torch.Tensor,
k_x: Optional[torch.Tensor] = None,
v_x: Optional[torch.Tensor] = None,
attn_mask: Optional[torch.Tensor] = None,
):
k_x = self.ln_1_kv(k_x) if hasattr(self, "ln_1_kv") and k_x is not None else None
v_x = self.ln_1_kv(v_x) if hasattr(self, "ln_1_kv") and v_x is not None else None
x = q_x + self.ls_1(self.attention(q_x=self.ln_1(q_x), k_x=k_x, v_x=v_x, attn_mask=attn_mask))
x = x + self.ls_2(self.mlp(self.ln_2(x)))
return x
class Transformer(nn.Module):
def __init__(
self,
width: int,
layers: int,
heads: int,
mlp_ratio: float = 4.0,
ls_init_value: float = None,
act_layer: Callable = nn.GELU,
norm_layer: Callable = LayerNorm,
):
super().__init__()
self.width = width
self.layers = layers
self.grad_checkpointing = False
self.resblocks = nn.ModuleList([
ResidualAttentionBlock(
width, heads, mlp_ratio, ls_init_value=ls_init_value, act_layer=act_layer, norm_layer=norm_layer)
for _ in range(layers)
])
def get_cast_dtype(self) -> torch.dtype:
if hasattr(self.resblocks[0].mlp.c_fc, 'int8_original_dtype'):
return self.resblocks[0].mlp.c_fc.int8_original_dtype
return self.resblocks[0].mlp.c_fc.weight.dtype
def forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
for r in self.resblocks:
if self.grad_checkpointing and not torch.jit.is_scripting():
# TODO: handle kwargs https://github.com/pytorch/pytorch/issues/79887#issuecomment-1161758372
x = checkpoint(r, x, None, None, attn_mask)
else:
x = r(x, attn_mask=attn_mask)
return x |