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 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 AttentionalPooler(nn.Module): def __init__( self, d_model: int, context_dim: int, n_head: int = 8, n_queries: int = 256, norm_layer: Callable = LayerNorm ): super().__init__() self.query = nn.Parameter(torch.randn(n_queries, d_model)) self.attn = nn.MultiheadAttention(d_model, n_head, kdim=context_dim, vdim=context_dim) self.ln_q = norm_layer(d_model) self.ln_k = norm_layer(context_dim) def forward(self, x: torch.Tensor): x = self.ln_k(x).permute(1, 0, 2) # NLD -> LND N = x.shape[1] q = self.ln_q(self.query) out = self.attn(self._repeat(q, N), x, x, need_weights=False)[0] return out.permute(1, 0, 2) # LND -> NLD def _repeat(self, query, N: int): return query.unsqueeze(1).repeat(1, N, 1) 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 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(): # 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 class VisionTransformer(nn.Module): output_tokens: torch.jit.Final[bool] 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, attentional_pool: bool = False, n_queries: int = 256, attn_pooler_heads: int = 8, output_dim: int = 512, patch_dropout: float = 0., input_patchnorm: bool = False, act_layer: Callable = nn.GELU, norm_layer: Callable = LayerNorm, output_tokens: bool = False ): super().__init__() self.output_tokens = output_tokens image_height, image_width = self.image_size = to_2tuple(image_size) patch_height, patch_width = self.patch_size = to_2tuple(patch_size) self.grid_size = (image_height // patch_height, image_width // patch_width) self.output_dim = output_dim # whether to layernorm each patch, as done in dual patchnorm paper - https://arxiv.org/abs/2302.01327v1 self.input_patchnorm = input_patchnorm if input_patchnorm: patch_input_dim = patch_height * patch_width * 3 self.patchnorm_pre_ln = LayerNorm(patch_input_dim) self.conv1 = nn.Linear(patch_input_dim, width) else: self.patchnorm_pre_ln = nn.Identity() self.conv1 = nn.Conv2d(in_channels=3, out_channels=width, kernel_size=patch_size, stride=patch_size, bias=False) # class embeddings and positional embeddings 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 if attentional_pool: self.attn_pool = AttentionalPooler(output_dim, width, n_head=attn_pooler_heads, n_queries=n_queries) self.ln_post = norm_layer(output_dim) self.proj = nn.Parameter(scale * torch.randn(output_dim, output_dim)) else: self.attn_pool = None 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 _global_pool(self, x: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]: if self.global_average_pool: return x.mean(dim=1), x else: return x[:, 0], x[:, 1:] def forward(self, x: torch.Tensor, skip_pool: bool = False): # to patches - whether to use dual patchnorm - https://arxiv.org/abs/2302.01327v1 if self.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.grid_size[0], self.patch_size[0], self.grid_size[1], self.patch_size[1]) x = x.permute(0, 2, 4, 1, 3, 5) x = x.reshape(x.shape[0], self.grid_size[0] * self.grid_size[1], -1) x = self.patchnorm_pre_ln(x) x = self.conv1(x) else: 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] # class embeddings and positional embeddings 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 skip_pool: return x if self.attn_pool is not None: x = self.attn_pool(x) x = self.ln_post(x) pooled, tokens = self._global_pool(x) else: pooled, tokens = self._global_pool(x) pooled = self.ln_post(pooled) if self.proj is not None: pooled = pooled @ self.proj if self.output_tokens: return pooled, tokens return pooled class TextTransformer(nn.Module): output_tokens: torch.jit.Final[bool] 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, embed_cls: bool = False, pad_id: int = 0, output_tokens: bool = False, ): super().__init__() self.output_tokens = output_tokens self.num_pos = self.context_length = context_length self.vocab_size = vocab_size self.width = width self.output_dim = output_dim self.heads = heads self.pad_id = pad_id self.text_projection = nn.Parameter(torch.empty(width, output_dim)) if embed_cls: self.cls_emb = nn.Parameter(torch.empty(width)) self.num_pos += 1 else: self.cls_emb = None self.token_embedding = nn.Embedding(vocab_size, width) self.positional_embedding = nn.Parameter(torch.empty(self.num_pos, 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.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) if self.cls_emb is not None: nn.init.normal_(self.cls_emb, 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 tokens # pytorch uses additive attention mask; fill with -inf mask = torch.empty(self.num_pos, self.num_pos) mask.fill_(float("-inf")) mask.triu_(1) # zero out the lower diagonal return mask def build_cls_mask(self, text, cast_dtype: torch.dtype): cls_mask = (text != self.pad_id).unsqueeze(1) cls_mask = F.pad(cls_mask, (1, 0, cls_mask.shape[2], 0), value=1.0) additive_mask = torch.empty(cls_mask.shape, dtype=cast_dtype, device=cls_mask.device) additive_mask.fill_(0) additive_mask.masked_fill_(~cls_mask, float("-inf")) additive_mask = torch.repeat_interleave(additive_mask, self.heads, 0) return additive_mask def _repeat(self, t, N: int): return t.reshape(1, 1, -1).repeat(N, 1, 1) def forward(self, text): cast_dtype = self.transformer.get_cast_dtype() seq_len = text.shape[1] x = self.token_embedding(text).to(cast_dtype) # [batch_size, n_ctx, d_model] attn_mask = self.attn_mask if self.cls_emb is not None: seq_len += 1 x = torch.cat([x, self._repeat(self.cls_emb, x.shape[0])], dim=1) cls_mask = self.build_cls_mask(text, cast_dtype) attn_mask = attn_mask[None, :seq_len, :seq_len] + cls_mask[:, :seq_len, :seq_len] x = x + self.positional_embedding[:seq_len].to(cast_dtype) x = x.permute(1, 0, 2) # NLD -> LND x = self.transformer(x, attn_mask=attn_mask) x = x.permute(1, 0, 2) # LND -> NLD # x.shape = [batch_size, n_ctx, transformer.width] # take features from the eot embedding (eot_token is the highest number in each sequence) if self.cls_emb is not None: pooled, tokens = x[:, -1], x[:, :-1] pooled = self.ln_final(pooled) else: x = self.ln_final(x) pooled, tokens = x[torch.arange(x.shape[0]), text.argmax(dim=-1)], x if self.text_projection is not None: pooled = pooled @ self.text_projection if self.output_tokens: return pooled, tokens return pooled class MultimodalTransformer(Transformer): def __init__( self, width: int, layers: int, heads: int, context_length: int = 77, mlp_ratio: float = 4.0, ls_init_value: float = None, act_layer: Callable = nn.GELU, norm_layer: Callable = LayerNorm, output_dim: int = 512, ): super().__init__( width=width, layers=layers, heads=heads, mlp_ratio=mlp_ratio, ls_init_value=ls_init_value, act_layer=act_layer, norm_layer=norm_layer, ) self.context_length = context_length self.cross_attn = nn.ModuleList([ ResidualAttentionBlock( width, heads, mlp_ratio, ls_init_value=ls_init_value, act_layer=act_layer, norm_layer=norm_layer, is_cross_attention=True, ) for _ in range(layers) ]) self.register_buffer('attn_mask', self.build_attention_mask(), persistent=False) self.ln_final = norm_layer(width) self.text_projection = nn.Parameter(torch.empty(width, output_dim)) def init_parameters(self): 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) for block in self.transformer.cross_attn: 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) def build_attention_mask(self): # lazily create causal attention mask, with full attention between the 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, image_embs, text_embs): text_embs = text_embs.permute(1, 0, 2) # NLD -> LNDsq image_embs = image_embs.permute(1, 0, 2) # NLD -> LND seq_len = text_embs.shape[0] for resblock, cross_attn in zip(self.resblocks, self.cross_attn): if self.grad_checkpointing and not torch.jit.is_scripting(): # TODO: handle kwargs https://github.com/pytorch/pytorch/issues/79887#issuecomment-1161758372 text_embs = checkpoint(resblock, text_embs, None, None, self.attn_mask[:seq_len, :seq_len]) text_embs = checkpoint(cross_attn, text_embs, image_embs, image_embs, None) else: text_embs = resblock(text_embs, attn_mask=self.attn_mask[:seq_len, :seq_len]) text_embs = cross_attn(text_embs, k_x=image_embs, v_x=image_embs) x = text_embs.permute(1, 0, 2) # LND -> NLD x = self.ln_final(x) if self.text_projection is not None: x = x @ self.text_projection return x @torch.jit.ignore def set_grad_checkpointing(self, enable=True): self.grad_checkpointing = enable