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mmpretrain.models.heads.spark_head 源代码

# Copyright (c) OpenMMLab. All rights reserved.
import torch
from mmengine.model import BaseModule

from mmpretrain.registry import MODELS


[文档]@MODELS.register_module() class SparKPretrainHead(BaseModule): """Pre-training head for SparK. Args: loss (dict): Config of loss. norm_pix (bool): Whether or not normalize target. Defaults to True. patch_size (int): Patch size, equal to downsample ratio of backbone. Defaults to 32. """ def __init__(self, loss: dict, norm_pix: bool = True, patch_size: int = 32) -> None: super().__init__() self.norm_pix = norm_pix self.patch_size = patch_size self.loss = MODELS.build(loss)
[文档] def patchify(self, imgs): """Split images into non-overlapped patches. Args: imgs (torch.Tensor): A batch of images, of shape B x C x H x W. Returns: torch.Tensor: Patchified images. The shape is B x L x D. """ p = self.patch_size assert len(imgs.shape ) == 4 and imgs.shape[2] % p == 0 and imgs.shape[3] % p == 0 B, C, ori_h, ori_w = imgs.shape h = ori_h // p w = ori_w // p x = imgs.reshape(shape=(B, C, h, p, w, p)) x = torch.einsum('bchpwq->bhwpqc', x) # (B, f*f, downsample_raito*downsample_raito*3) x = x.reshape(shape=(B, h * w, p**2 * C)) return x
[文档] def construct_target(self, target: torch.Tensor) -> torch.Tensor: """Construct the reconstruction target. In addition to splitting images into tokens, this module will also normalize the image according to ``norm_pix``. Args: target (torch.Tensor): Image with the shape of B x 3 x H x W Returns: torch.Tensor: Tokenized images with the shape of B x L x C """ target = self.patchify(target) if self.norm_pix: # normalize the target image mean = target.mean(dim=-1, keepdim=True) var = target.var(dim=-1, keepdim=True) target = (target - mean) / (var + 1.e-6)**.5 return target
[文档] def forward(self, pred: torch.Tensor, target: torch.Tensor, active_mask: torch.Tensor) -> torch.Tensor: """Forward function of MAE head. Args: pred (torch.Tensor): The reconstructed image. target (torch.Tensor): The target image. active_mask (torch.Tensor): The mask of the target image. Returns: torch.Tensor: The reconstruction loss. """ # (B, C, H, W) -> (B, L, C) and perform normalization target = self.construct_target(target) # (B, C, H, W) -> (B, L, C) pred = self.patchify(pred) # (B, 1, f, f) -> (B, L) non_active_mask = active_mask.logical_not().int().view( active_mask.shape[0], -1) # MSE loss on masked patches loss = self.loss(pred, target, non_active_mask) return loss
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