""" CLIP Model
Adapted from https://github.com/openai/CLIP. Originally MIT License, Copyright (c) 2021 OpenAI.
"""
from dataclasses import dataclass
import logging
import math
from typing import Optional, Tuple, Union
import numpy as np
import torch
import torch.nn.functional as F
from torch import nn
from .transformer import LayerNormFp32, LayerNorm, QuickGELU, Attention, VisionTransformer, TextTransformer
from .utils import to_2tuple
@dataclass
class CLIPVisionCfg:
layers: Union[Tuple[int, int, int, int], int] = 12
width: int = 768
head_width: int = 64
mlp_ratio: float = 4.0
patch_size: int = 16
image_size: Union[Tuple[int, int], int] = 224
ls_init_value: Optional[float] = None # layer scale initial value
patch_dropout: float = 0. # what fraction of patches to dropout during training (0 would mean disabled and no patches dropped) - 0.5 to 0.75 recommended in the paper for optimal results
input_patchnorm: bool = False # whether to use dual patchnorm - would only apply the input layernorm on each patch, as post-layernorm already exist in original clip vit design
global_average_pool: bool = False # whether to global average pool the last embedding layer, instead of using CLS token (https://arxiv.org/abs/2205.01580)
attentional_pool: bool = False # whether to use attentional pooler in the last embedding layer
n_queries: int = 256 # n_queries for attentional pooler
attn_pooler_heads: int = 8 # n heads for attentional_pooling
timm_model_name: str = None # a valid model name overrides layers, width, patch_size
timm_model_pretrained: bool = False # use (imagenet) pretrained weights for named model
timm_pool: str = 'avg' # feature pooling for timm model ('abs_attn', 'rot_attn', 'avg', '')
timm_proj: str = 'linear' # linear projection for timm model output ('linear', 'mlp', '')
timm_proj_bias: bool = False # enable bias final projection
timm_drop: float = 0. # head dropout
timm_drop_path: Optional[float] = None # backbone stochastic depth
output_tokens: bool = False
@dataclass
class CLIPTextCfg:
context_length: int = 77
vocab_size: int = 49408
width: int = 512
heads: int = 8
layers: int = 12
ls_init_value: Optional[float] = None # layer scale initial value
hf_model_name: str = None
hf_tokenizer_name: str = None
hf_model_pretrained: bool = True
proj: str = 'mlp'
pooler_type: str = 'mean_pooler'
embed_cls: bool = False
pad_id: int = 0
output_tokens: bool = False
def get_cast_dtype(precision: str):
cast_dtype = None
if precision == 'bf16':
cast_dtype = torch.bfloat16
elif precision == 'fp16':
cast_dtype = torch.float16
return cast_dtype
def _build_vision_tower(
embed_dim: int,
vision_cfg: CLIPVisionCfg,
quick_gelu: bool = False,
cast_dtype: Optional[torch.dtype] = None,
):
if isinstance(vision_cfg, dict):
vision_cfg = CLIPVisionCfg(**vision_cfg)
# OpenAI models are pretrained w/ QuickGELU but native nn.GELU is both faster and more
# memory efficient in recent PyTorch releases (>= 1.10).
# NOTE: timm models always use native GELU regardless of quick_gelu flag.
act_layer = QuickGELU if quick_gelu else nn.GELU
vision_heads = vision_cfg.width // vision_cfg.head_width
norm_layer = LayerNormFp32 if cast_dtype in (torch.float16, torch.bfloat16) else LayerNorm
visual = VisionTransformer(
image_size=vision_cfg.image_size,
patch_size=vision_cfg.patch_size,
width=vision_cfg.width,
layers=vision_cfg.layers,
heads=vision_heads,
mlp_ratio=vision_cfg.mlp_ratio,
ls_init_value=vision_cfg.ls_init_value,
patch_dropout=vision_cfg.patch_dropout,
input_patchnorm=vision_cfg.input_patchnorm,
global_average_pool=vision_cfg.global_average_pool,
attentional_pool=vision_cfg.attentional_pool,
n_queries=vision_cfg.n_queries,
attn_pooler_heads=vision_cfg.attn_pooler_heads,
output_tokens=vision_cfg.output_tokens,
output_dim=embed_dim,
act_layer=act_layer,
norm_layer=norm_layer
)
return visual
def _build_text_tower(
embed_dim: int,
text_cfg: CLIPTextCfg,
quick_gelu: bool = False,
cast_dtype: Optional[torch.dtype] = None,
):
if isinstance(text_cfg, dict):
text_cfg = CLIPTextCfg(**text_cfg)
act_layer = QuickGELU if quick_gelu else nn.GELU
norm_layer = LayerNormFp32 if cast_dtype in (torch.float16, torch.bfloat16) else LayerNorm
text = TextTransformer(
context_length=text_cfg.context_length,
vocab_size=text_cfg.vocab_size,
width=text_cfg.width,
heads=text_cfg.heads,
layers=text_cfg.layers,
ls_init_value=text_cfg.ls_init_value,
output_dim=embed_dim,
embed_cls=text_cfg.embed_cls,
output_tokens=text_cfg.output_tokens,
pad_id=text_cfg.pad_id,
act_layer=act_layer,
norm_layer=norm_layer
)
return text
class CLIP(nn.Module):
output_dict: torch.jit.Final[bool]
def __init__(
self,
embed_dim: int,
vision_cfg: CLIPVisionCfg,
text_cfg: CLIPTextCfg,
quick_gelu: bool = False,
cast_dtype: Optional[torch.dtype] = None,
output_dict: bool = False,
):
super().__init__()
self.output_dict = output_dict
self.visual = _build_vision_tower(embed_dim, vision_cfg, quick_gelu, cast_dtype)
text = _build_text_tower(embed_dim, text_cfg, quick_gelu, cast_dtype)
self.transformer = text.transformer
self.vocab_size = text.vocab_size
self.token_embedding = text.token_embedding
self.positional_embedding = text.positional_embedding
self.ln_final = text.ln_final
self.text_projection = text.text_projection
self.register_buffer('attn_mask', text.attn_mask, persistent=False)
self.logit_scale = nn.Parameter(torch.ones([]) * np.log(1 / 0.07))
def lock_image_tower(self, unlocked_groups=0, freeze_bn_stats=False):
# lock image tower as per LiT - https://arxiv.org/abs/2111.07991
self.visual.lock(unlocked_groups=unlocked_groups, freeze_bn_stats=freeze_bn_stats)
@torch.jit.ignore
def set_grad_checkpointing(self, enable=True):
self.visual.set_grad_checkpointing(enable)
self.transformer.grad_checkpointing = enable
def encode_image(self, image, out_layers):
x = image
# to patches - whether to use dual patchnorm - https://arxiv.org/abs/2302.01327v1
if self.visual.input_patchnorm:
# einops - rearrange(x, 'b c (h p1) (w p2) -> b (h w) (c p1 p2)')
x = x.reshape(x.shape[0], x.shape[1],
self.visual.grid_size[0],
self.visual.patch_size[0],
self.visual.grid_size[1],
self.visual.patch_size[1])
x = x.permute(0, 2, 4, 1, 3, 5)
x = x.reshape(x.shape[0], self.visual.grid_size[0] * self.visual.grid_size[1], -1)
x = self.visual.patchnorm_pre_ln(x)
x = self.visual.conv1(x)
else:
x = self.visual.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]
# class embeddings and positional embeddings
x = torch.cat(
[self.visual.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.visual.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.visual.patch_dropout(x)
x = self.visual.ln_pre(x)
x = x.permute(1, 0, 2) # NLD -> LND
patch_tokens = []
idx = 0
for r in self.visual.transformer.resblocks:
idx += 1
# add prompt here
x, attn_tmp = r(x, attn_mask=None)
if idx in out_layers:
patch_tokens.append(x)
x = x.permute(1, 0, 2) # LND -> NLD
patch_tokens = [patch_tokens[t].permute(1, 0, 2) for t in range(len(patch_tokens))] # LND -> NLD
if self.visual.attn_pool is not None:
x = self.visual.attn_pool(x)
x = self.visual.ln_post(x)
pooled, tokens = self.visual._global_pool(x)
else:
pooled, tokens = self.visual._global_pool(x)
pooled = self.visual.ln_post(pooled)
if self.visual.proj is not None:
pooled = pooled @ self.visual.proj
if self.visual.output_tokens:
return pooled, patch_tokens
return pooled, patch_tokens
def encode_text(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
for r in self.visual.transformer.resblocks:
# add prompt here
x, attn_tmp = r(x, attn_mask=self.attn_mask)
x = x.permute(1, 0, 2) # LND -> NLD
x = self.ln_final(x) # [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
def convert_weights_to_lp(model: nn.Module, dtype=torch.float16):
"""Convert applicable model parameters to low-precision (bf16 or fp16)"""
def _convert_weights(l):
if isinstance(l, (nn.Conv1d, nn.Conv2d, nn.Linear)):
l.weight.data = l.weight.data.to(dtype)
if l.bias is not None:
l.bias.data = l.bias.data.to(dtype)
if isinstance(l, (nn.MultiheadAttention, Attention)):
for attr in [*[f"{s}_proj_weight" for s in ["in", "q", "k", "v"]], "in_proj_bias", "bias_k", "bias_v"]:
tensor = getattr(l, attr)
if tensor is not None:
tensor.data = tensor.data.to(dtype)
for name in ["text_projection", "proj"]:
if hasattr(l, name):
attr = getattr(l, name)
if attr is not None:
attr.data = attr.data.to(dtype)
model.apply(_convert_weights)
convert_weights_to_fp16 = convert_weights_to_lp # backwards compat
# used to maintain checkpoint compatibility
def convert_to_custom_text_state_dict(state_dict: dict):
if 'text_projection' in state_dict:
# old format state_dict, move text tower -> .text
new_state_dict = {}
for k, v in state_dict.items():
if any(k.startswith(p) for p in (
'text_projection',
'positional_embedding',
'token_embedding',
'transformer',
'ln_final',
)):
k = 'text.' + k
new_state_dict[k] = v
return new_state_dict
return state_dict
def build_model_from_openai_state_dict(
state_dict: dict,
quick_gelu=True,
cast_dtype=torch.float16,
):
vit = "visual.proj" in state_dict
if vit:
vision_width = state_dict["visual.conv1.weight"].shape[0]
vision_layers = len(
[k for k in state_dict.keys() if k.startswith("visual.") and k.endswith(".attn.in_proj_weight")])
vision_patch_size = state_dict["visual.conv1.weight"].shape[-1]
grid_size = round((state_dict["visual.positional_embedding"].shape[0] - 1) ** 0.5)
image_size = vision_patch_size * grid_size
else:
counts: list = [
len(set(k.split(".")[2] for k in state_dict if k.startswith(f"visual.layer{b}"))) for b in [1, 2, 3, 4]]
vision_layers = tuple(counts)
vision_width = state_dict["visual.layer1.0.conv1.weight"].shape[0]
output_width = round((state_dict["visual.attnpool.positional_embedding"].shape[0] - 1) ** 0.5)
vision_patch_size = None
assert output_width ** 2 + 1 == state_dict["visual.attnpool.positional_embedding"].shape[0]
image_size = output_width * 32
embed_dim = state_dict["text_projection"].shape[1]
context_length = state_dict["positional_embedding"].shape[0]
vocab_size = state_dict["token_embedding.weight"].shape[0]
transformer_width = state_dict["ln_final.weight"].shape[0]
transformer_heads = transformer_width // 64
transformer_layers = len(set(k.split(".")[2] for k in state_dict if k.startswith(f"transformer.resblocks")))
vision_cfg = CLIPVisionCfg(
layers=vision_layers,
width=vision_width,
patch_size=vision_patch_size,
image_size=image_size,
)
text_cfg = CLIPTextCfg(
context_length=context_length,
vocab_size=vocab_size,
width=transformer_width,
heads=transformer_heads,
layers=transformer_layers,
)
model = CLIP(
embed_dim,
vision_cfg=vision_cfg,
text_cfg=text_cfg,
quick_gelu=quick_gelu, # OpenAI models were trained with QuickGELU
cast_dtype=cast_dtype,
)
for key in ["input_resolution", "context_length", "vocab_size"]:
state_dict.pop(key, None)
convert_weights_to_fp16(model) # OpenAI state dicts are partially converted to float16
model.load_state_dict(state_dict)
return model.eval()
def trace_model(model, batch_size=256, device=torch.device('cpu')):
model.eval()
image_size = model.visual.image_size
example_images = torch.ones((batch_size, 3, image_size, image_size), device=device)
example_text = torch.zeros((batch_size, model.context_length), dtype=torch.int, device=device)
model = torch.jit.trace_module(
model,
inputs=dict(
forward=(example_images, example_text),
encode_text=(example_text,),
encode_image=(example_images,)
))
model.visual.image_size = image_size
return model
def resize_pos_embed(state_dict, model, interpolation: str = 'bicubic'):
# Rescale the grid of position embeddings when loading from state_dict
old_pos_embed = state_dict.get('visual.positional_embedding', None)
if old_pos_embed is None or not hasattr(model.visual, 'grid_size'):
return
grid_size = to_2tuple(model.visual.grid_size)
extra_tokens = 1 # FIXME detect different token configs (ie no class token, or more)
new_seq_len = grid_size[0] * grid_size[1] + extra_tokens
if new_seq_len == old_pos_embed.shape[0]:
return
if extra_tokens:
pos_emb_tok, pos_emb_img = old_pos_embed[:extra_tokens], old_pos_embed[extra_tokens:]
else:
pos_emb_tok, pos_emb_img = None, old_pos_embed
old_grid_size = to_2tuple(int(math.sqrt(len(pos_emb_img))))
logging.info('Resizing position embedding grid-size from %s to %s', old_grid_size, grid_size)
pos_emb_img = pos_emb_img.reshape(1, old_grid_size[0], old_grid_size[1], -1).permute(0, 3, 1, 2)
pos_emb_img = F.interpolate(
pos_emb_img,
size=grid_size,
mode=interpolation,
align_corners=False,
)
pos_emb_img = pos_emb_img.permute(0, 2, 3, 1).reshape(1, grid_size[0] * grid_size[1], -1)[0]
if pos_emb_tok is not None:
new_pos_embed = torch.cat([pos_emb_tok, pos_emb_img], dim=0)
else:
new_pos_embed = pos_emb_img
state_dict['visual.positional_embedding'] = new_pos_embed