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