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8.56 kB
| # Copyright (c) Meta Platforms, Inc. and affiliates. | |
| # All rights reserved. | |
| # | |
| # This source code is licensed under the license found in the | |
| # LICENSE file in the root directory of this source tree. | |
| # | |
| import math | |
| from functools import partial | |
| import torch | |
| import torch.nn as nn | |
| from src.models.utils.modules import Block | |
| from src.models.utils.pos_embs import get_2d_sincos_pos_embed, get_3d_sincos_pos_embed | |
| from src.utils.tensors import ( | |
| trunc_normal_, | |
| repeat_interleave_batch | |
| ) | |
| from src.masks.utils import apply_masks | |
| class VisionTransformerPredictor(nn.Module): | |
| """ Vision Transformer """ | |
| def __init__( | |
| self, | |
| img_size=224, | |
| patch_size=16, | |
| num_frames=1, | |
| tubelet_size=2, | |
| embed_dim=768, | |
| predictor_embed_dim=384, | |
| depth=6, | |
| num_heads=12, | |
| mlp_ratio=4.0, | |
| qkv_bias=True, | |
| qk_scale=None, | |
| drop_rate=0.0, | |
| attn_drop_rate=0.0, | |
| norm_layer=nn.LayerNorm, | |
| init_std=0.02, | |
| uniform_power=False, | |
| use_mask_tokens=False, | |
| num_mask_tokens=2, | |
| zero_init_mask_tokens=True, | |
| **kwargs | |
| ): | |
| super().__init__() | |
| # Map input to predictor dimension | |
| self.predictor_embed = nn.Linear(embed_dim, predictor_embed_dim, bias=True) | |
| # Mask tokens | |
| self.mask_tokens = None | |
| self.num_mask_tokens = 0 | |
| if use_mask_tokens: | |
| self.num_mask_tokens = num_mask_tokens | |
| self.mask_tokens = nn.ParameterList([ | |
| nn.Parameter(torch.zeros(1, 1, predictor_embed_dim)) | |
| for i in range(num_mask_tokens) | |
| ]) | |
| # Determine positional embedding | |
| self.input_size = img_size | |
| self.patch_size = patch_size | |
| # -- | |
| self.num_frames = num_frames | |
| self.tubelet_size = tubelet_size | |
| self.is_video = num_frames > 1 | |
| grid_size = self.input_size // self.patch_size | |
| grid_depth = self.num_frames // self.tubelet_size | |
| if self.is_video: | |
| self.num_patches = num_patches = ( | |
| (num_frames // tubelet_size) | |
| * (img_size // patch_size) | |
| * (img_size // patch_size) | |
| ) | |
| else: | |
| self.num_patches = num_patches = ( | |
| (img_size // patch_size) | |
| * (img_size // patch_size) | |
| ) | |
| # Position embedding | |
| self.uniform_power = uniform_power | |
| self.predictor_pos_embed = None | |
| self.predictor_pos_embed = nn.Parameter( | |
| torch.zeros(1, num_patches, predictor_embed_dim), | |
| requires_grad=False) | |
| # Attention Blocks | |
| self.predictor_blocks = nn.ModuleList([ | |
| Block( | |
| dim=predictor_embed_dim, | |
| num_heads=num_heads, | |
| mlp_ratio=mlp_ratio, | |
| qkv_bias=qkv_bias, | |
| qk_scale=qk_scale, | |
| drop=drop_rate, | |
| act_layer=nn.GELU, | |
| attn_drop=attn_drop_rate, | |
| grid_size=grid_size, | |
| grid_depth=grid_depth, | |
| norm_layer=norm_layer) | |
| for i in range(depth)]) | |
| # Normalize & project back to input dimension | |
| self.predictor_norm = norm_layer(predictor_embed_dim) | |
| self.predictor_proj = nn.Linear(predictor_embed_dim, embed_dim, bias=True) | |
| # ------ initialize weights | |
| if self.predictor_pos_embed is not None: | |
| self._init_pos_embed(self.predictor_pos_embed.data) # sincos pos-embed | |
| self.init_std = init_std | |
| if not zero_init_mask_tokens: | |
| for mt in self.mask_tokens: | |
| trunc_normal_(mt, std=init_std) | |
| self.apply(self._init_weights) | |
| self._rescale_blocks() | |
| def _init_pos_embed(self, pos_embed): | |
| embed_dim = pos_embed.size(-1) | |
| grid_size = self.input_size // self.patch_size | |
| if self.is_video: | |
| grid_depth = self.num_frames // self.tubelet_size | |
| sincos = get_3d_sincos_pos_embed( | |
| embed_dim, | |
| grid_size, | |
| grid_depth, | |
| cls_token=False, | |
| uniform_power=self.uniform_power | |
| ) | |
| else: | |
| sincos = get_2d_sincos_pos_embed(embed_dim, grid_size, cls_token=False) | |
| pos_embed.copy_(torch.from_numpy(sincos).float().unsqueeze(0)) | |
| def _init_weights(self, m): | |
| if isinstance(m, nn.Linear): | |
| trunc_normal_(m.weight, std=self.init_std) | |
| if isinstance(m, nn.Linear) and m.bias is not None: | |
| nn.init.constant_(m.bias, 0) | |
| elif isinstance(m, nn.LayerNorm): | |
| nn.init.constant_(m.bias, 0) | |
| nn.init.constant_(m.weight, 1.0) | |
| def _rescale_blocks(self): | |
| def rescale(param, layer_id): | |
| param.div_(math.sqrt(2.0 * layer_id)) | |
| for layer_id, layer in enumerate(self.predictor_blocks): | |
| rescale(layer.attn.proj.weight.data, layer_id + 1) | |
| rescale(layer.mlp.fc2.weight.data, layer_id + 1) | |
| def diffusion(self, x, noise_beta=(0.5, 1.0), steps=1000): | |
| # Prepare diffusion noise schedule | |
| b1, b2 = noise_beta | |
| beta_scheduler = (b1 + i*(b2-b1)/steps for i in range(steps)) | |
| alpha_scheduler = [] | |
| _alpha = 1.0 | |
| for _beta in beta_scheduler: | |
| _alpha *= 1.-_beta | |
| alpha_scheduler += [_alpha] | |
| # Sample diffusion time step | |
| T = torch.randint(0, steps, (len(x),)) | |
| alpha = torch.tensor(alpha_scheduler, device=x.device)[T].unsqueeze(-1).unsqueeze(-1) | |
| # Normalize features and apply noise | |
| x = torch.nn.functional.layer_norm(x, (x.size(-1),)) | |
| x = alpha**0.5 * x + (1.-alpha)**0.5 * torch.randn(x.shape, device=x.device) | |
| return x | |
| def forward(self, ctxt, tgt, masks_ctxt, masks_tgt, mask_index=1): | |
| """ | |
| :param ctxt: context tokens | |
| :param tgt: target tokens | |
| :param masks_ctxt: indices of context tokens in input | |
| :params masks_tgt: indices of target tokens in input | |
| """ | |
| assert (masks_ctxt is not None) and (masks_tgt is not None), 'Cannot run predictor without mask indices' | |
| if not isinstance(masks_ctxt, list): | |
| masks_ctxt = [masks_ctxt] | |
| if not isinstance(masks_tgt, list): | |
| masks_tgt = [masks_tgt] | |
| # Batch Size | |
| B = len(ctxt) // len(masks_ctxt) | |
| # Map context tokens to pedictor dimensions | |
| x = self.predictor_embed(ctxt) | |
| _, N_ctxt, D = x.shape | |
| # Add positional embedding to ctxt tokens | |
| if self.predictor_pos_embed is not None: | |
| ctxt_pos_embed = self.predictor_pos_embed.repeat(B, 1, 1) | |
| x += apply_masks(ctxt_pos_embed, masks_ctxt) | |
| # Map target tokens to predictor dimensions & add noise (fwd diffusion) | |
| if self.mask_tokens is None: | |
| pred_tokens = self.predictor_embed(tgt) | |
| pred_tokens = self.diffusion(pred_tokens) | |
| else: | |
| mask_index = mask_index % self.num_mask_tokens | |
| pred_tokens = self.mask_tokens[mask_index] | |
| pred_tokens = pred_tokens.repeat(B, self.num_patches, 1) | |
| pred_tokens = apply_masks(pred_tokens, masks_tgt) | |
| # Add positional embedding to target tokens | |
| if self.predictor_pos_embed is not None: | |
| pos_embs = self.predictor_pos_embed.repeat(B, 1, 1) | |
| pos_embs = apply_masks(pos_embs, masks_tgt) | |
| pos_embs = repeat_interleave_batch(pos_embs, B, repeat=len(masks_ctxt)) | |
| pred_tokens += pos_embs | |
| # Concatenate context & target tokens | |
| x = x.repeat(len(masks_tgt), 1, 1) | |
| x = torch.cat([x, pred_tokens], dim=1) | |
| # FIXME: this implementation currently assumes masks_ctxt and masks_tgt | |
| # are alligned 1:1 (ok with MultiMask wrapper on predictor but | |
| # otherwise will break) | |
| masks_ctxt = torch.cat(masks_ctxt, dim=0) | |
| masks_tgt = torch.cat(masks_tgt, dim=0) | |
| masks = torch.cat([masks_ctxt, masks_tgt], dim=1) | |
| # Fwd prop | |
| for blk in self.predictor_blocks: | |
| x = blk(x, mask=masks) | |
| x = self.predictor_norm(x) | |
| # Return output corresponding to target tokens | |
| x = x[:, N_ctxt:] | |
| x = self.predictor_proj(x) | |
| return x | |
| def vit_predictor(**kwargs): | |
| model = VisionTransformerPredictor( | |
| mlp_ratio=4, qkv_bias=True, norm_layer=partial(nn.LayerNorm, eps=1e-6), | |
| **kwargs) | |
| return model | |