dinov2_base/model.py

"""
OurNet Model Definition with DINOv2 backbone

Uses transformers.AutoModel to load DINOv2-base
"""

import torch
import torch.nn as nn
from transformers import AutoModel


class OurNet(nn.Module):
    def __init__(self, config=None):
        super().__init__()

        # DINOv2 model from HuggingFace
        self.backbone = AutoModel.from_pretrained(
            'facebook/dinov2-base',
            local_files_only=True
        )

        # Feature dimension for DINOv2-base
        self.n_features = 768

        # Projection dimension from config
        self.proj_dim = config.get('proj_dim', 768) if config else 768

        # Auxiliary projection heads (for Stage 1)
        self.aux_fc1 = nn.Sequential(
            nn.Linear(self.n_features, self.n_features),
            nn.ReLU(),
            nn.Linear(self.n_features, self.proj_dim)
        )

        self.aux_fc2 = nn.Sequential(
            nn.Linear(self.n_features, self.n_features),
            nn.ReLU(),
            nn.Linear(self.n_features, self.proj_dim)
        )

        # Detection heads (for Stage 2)
        self.det_fc1 = nn.Sequential(
            nn.Linear(self.n_features, self.n_features),
            nn.ReLU(),
            nn.Linear(self.n_features, self.proj_dim)
        )

        self.det_fc2 = nn.Sequential(
            nn.Linear(self.n_features, 256),
            nn.ReLU(inplace=True),
            nn.Dropout(0.5),
            nn.Linear(256, 1)
        )

    def forward_proj(self, x):
        """Forward pass for auxiliary projection (Stage 1)"""
        outputs = self.backbone(x)
        feats = outputs.last_hidden_state[:, 0]  # CLS token
        heter_head = self.aux_fc1(feats)
        homo_head = self.aux_fc2(feats)
        return heter_head, homo_head

    def forward_det(self, x):
        """Forward pass for detection (Stage 2)"""
        outputs = self.backbone(x)
        feats = outputs.last_hidden_state[:, 0]  # CLS token
        homo_head = self.det_fc1(feats)
        det_head = self.det_fc2(feats)
        return homo_head, det_head