pez-dispenser / open_clip /transformer.py
ywen's picture
initial commit
2f43921
from collections import OrderedDict
import math
from typing import Callable, Optional, Sequence
import torch
from torch import nn
from torch.nn import functional as F
from torch.utils.checkpoint import checkpoint
from .utils import to_2tuple
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,
):
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()
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, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
attn_mask = attn_mask.to(x.dtype) if attn_mask is not None else None
return self.attn(x, x, x, need_weights=False, attn_mask=attn_mask)[0]
def forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
x = x + self.ls_1(self.attention(self.ln_1(x), attn_mask=attn_mask))
x = x + self.ls_2(self.mlp(self.ln_2(x)))
return x
class CustomResidualAttentionBlock(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,
scale_cosine_attn: bool = False,
scale_heads: bool = False,
scale_attn: bool = False,
scale_fc: bool = False,
):
super().__init__()
self.ln_1 = norm_layer(d_model)
self.attn = Attention(
d_model, n_head,
scaled_cosine=scale_cosine_attn,
scale_heads=scale_heads,
)
self.ln_attn = norm_layer(d_model) if scale_attn else nn.Identity()
self.ls_1 = LayerScale(d_model, ls_init_value) if ls_init_value is not None else nn.Identity()
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)),
('ln', norm_layer(mlp_width) if scale_fc else nn.Identity()),
("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 forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
x = x + self.ls_1(self.ln_attn(self.attn(self.ln_1(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:
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():
x = checkpoint(r, x, attn_mask)
else:
x = r(x, attn_mask=attn_mask)
return x
class VisionTransformer(nn.Module):
def __init__(
self,
image_size: int,
patch_size: int,
width: int,
layers: int,
heads: int,
mlp_ratio: float,
ls_init_value: float = None,
global_average_pool: bool = False,
output_dim: int = 512,
patch_dropout: float = 0.,
act_layer: Callable = nn.GELU,
norm_layer: Callable = LayerNorm,
):
super().__init__()
self.image_size = to_2tuple(image_size)
self.patch_size = to_2tuple(patch_size)
self.grid_size = (self.image_size[0] // self.patch_size[0], self.image_size[1] // self.patch_size[1])
self.output_dim = output_dim
self.conv1 = nn.Conv2d(in_channels=3, out_channels=width, kernel_size=patch_size, stride=patch_size, bias=False)
scale = width ** -0.5
self.class_embedding = nn.Parameter(scale * torch.randn(width))
self.positional_embedding = nn.Parameter(scale * torch.randn(self.grid_size[0] * self.grid_size[1] + 1, width))
# setting a patch_dropout of 0. would mean it is disabled and this function would be the identity fn
self.patch_dropout = PatchDropout(patch_dropout) if patch_dropout > 0. else nn.Identity()
self.ln_pre = norm_layer(width)
self.transformer = Transformer(
width,
layers,
heads,
mlp_ratio,
ls_init_value=ls_init_value,
act_layer=act_layer,
norm_layer=norm_layer,
)
self.global_average_pool = global_average_pool
self.ln_post = norm_layer(width)
self.proj = nn.Parameter(scale * torch.randn(width, output_dim))
self.init_parameters()
def lock(self, unlocked_groups=0, freeze_bn_stats=False):
for param in self.parameters():
param.requires_grad = False
if unlocked_groups != 0:
groups = [
[
self.conv1,
self.class_embedding,
self.positional_embedding,
self.ln_pre,
],
*self.transformer.resblocks[:-1],
[
self.transformer.resblocks[-1],
self.ln_post,
],
self.proj,
]
def _unlock(x):
if isinstance(x, Sequence):
for g in x:
_unlock(g)
else:
if isinstance(x, torch.nn.Parameter):
x.requires_grad = True
else:
for p in x.parameters():
p.requires_grad = True
_unlock(groups[-unlocked_groups:])
def init_parameters(self):
# FIXME OpenAI CLIP did not define an init for the VisualTransformer
# TODO experiment if default PyTorch init, below, or alternate init is best.
# nn.init.normal_(self.class_embedding, std=self.scale)
# nn.init.normal_(self.positional_embedding, std=self.scale)
#
# proj_std = (self.transformer.width ** -0.5) * ((2 * self.transformer.layers) ** -0.5)
# attn_std = self.transformer.width ** -0.5
# fc_std = (2 * self.transformer.width) ** -0.5
# for block in self.transformer.resblocks:
# nn.init.normal_(block.attn.in_proj_weight, std=attn_std)
# nn.init.normal_(block.attn.out_proj.weight, std=proj_std)
# nn.init.normal_(block.mlp.c_fc.weight, std=fc_std)
# nn.init.normal_(block.mlp.c_proj.weight, std=proj_std)
#
# if self.text_projection is not None:
# nn.init.normal_(self.text_projection, std=self.scale)
pass
@torch.jit.ignore
def set_grad_checkpointing(self, enable=True):
self.transformer.grad_checkpointing = enable
def forward(self, x: torch.Tensor):
x = self.conv1(x) # shape = [*, width, grid, grid]
x = x.reshape(x.shape[0], x.shape[1], -1) # shape = [*, width, grid ** 2]
x = x.permute(0, 2, 1) # shape = [*, grid ** 2, width]
x = torch.cat(
[self.class_embedding.to(x.dtype) + torch.zeros(x.shape[0], 1, x.shape[-1], dtype=x.dtype, device=x.device),
x], dim=1) # shape = [*, grid ** 2 + 1, width]
x = x + self.positional_embedding.to(x.dtype)
# a patch_dropout of 0. would mean it is disabled and this function would do nothing but return what was passed in
x = self.patch_dropout(x)
x = self.ln_pre(x)
x = x.permute(1, 0, 2) # NLD -> LND
x = self.transformer(x)
x = x.permute(1, 0, 2) # LND -> NLD
if self.global_average_pool:
x = x.mean(dim=1)
else:
x = x[:, 0]
x = self.ln_post(x)
if self.proj is not None:
x = x @ self.proj
return x
class TextTransformer(nn.Module):
def __init__(
self,
context_length: int = 77,
vocab_size: int = 49408,
width: int = 512,
heads: int = 8,
layers: int = 12,
ls_init_value: float = None,
output_dim: int = 512,
act_layer: Callable = nn.GELU,
norm_layer: Callable = LayerNorm,
):
super().__init__()
self.context_length = context_length
self.vocab_size = vocab_size
self.width = width
self.output_dim = output_dim
self.token_embedding = nn.Embedding(vocab_size, width)
self.positional_embedding = nn.Parameter(torch.empty(self.context_length, width))
self.transformer = Transformer(
width=width,
layers=layers,
heads=heads,
ls_init_value=ls_init_value,
act_layer=act_layer,
norm_layer=norm_layer,
)
self.ln_final = norm_layer(width)
self.text_projection = nn.Parameter(torch.empty(width, output_dim))
self.register_buffer('attn_mask', self.build_attention_mask(), persistent=False)
self.init_parameters()
def init_parameters(self):
nn.init.normal_(self.token_embedding.weight, std=0.02)
nn.init.normal_(self.positional_embedding, std=0.01)
proj_std = (self.transformer.width ** -0.5) * ((2 * self.transformer.layers) ** -0.5)
attn_std = self.transformer.width ** -0.5
fc_std = (2 * self.transformer.width) ** -0.5
for block in self.transformer.resblocks:
nn.init.normal_(block.attn.in_proj_weight, std=attn_std)
nn.init.normal_(block.attn.out_proj.weight, std=proj_std)
nn.init.normal_(block.mlp.c_fc.weight, std=fc_std)
nn.init.normal_(block.mlp.c_proj.weight, std=proj_std)
if self.text_projection is not None:
nn.init.normal_(self.text_projection, std=self.transformer.width ** -0.5)
@torch.jit.ignore
def set_grad_checkpointing(self, enable=True):
self.transformer.grad_checkpointing = enable
def build_attention_mask(self):
# lazily create causal attention mask, with full attention between the vision tokens
# pytorch uses additive attention mask; fill with -inf
mask = torch.empty(self.context_length, self.context_length)
mask.fill_(float("-inf"))
mask.triu_(1) # zero out the lower diagonal
return mask
def forward(self, text):
cast_dtype = self.transformer.get_cast_dtype()
x = self.token_embedding(text).to(cast_dtype) # [batch_size, n_ctx, d_model]
x = x + self.positional_embedding.to(cast_dtype)
x = x.permute(1, 0, 2) # NLD -> LND
x = self.transformer(x, attn_mask=self.attn_mask)
x = x.permute(1, 0, 2) # LND -> NLD
x = self.ln_final(x)
# x.shape = [batch_size, n_ctx, transformer.width]
# take features from the eot embedding (eot_token is the highest number in each sequence)
x = x[torch.arange(x.shape[0]), text.argmax(dim=-1)] @ self.text_projection
return x