DsJASPREET/mobilenetv2-cats-dogs-classifier

🐱🐶 MobileNetV2 — Cat vs Dog Image Classifier

The shortest accurate model possible — 3.5M parameters, ~13.5 MB on disk, 85%+ validation accuracy

📋 Model Summary

Property	Value
Architecture	MobileNetV2
Base Checkpoint	google/mobilenet_v2_1.0_224
Total Parameters	~3,504,872
Model Size (FP32)	~13.37 MB
Input Resolution	224 × 224
Num Classes	2 (cat, dog)
Framework	PyTorch + HuggingFace Transformers

Why MobileNetV2?

MobileNetV2 is the smallest viable architecture that achieves 85%+ accuracy on cats vs dogs:

• Inverted residual blocks with depthwise separable convolutions — 10× fewer FLOPs than standard convolutions
• Linear bottlenecks prevent information loss in low-dimensional representations
• Only 3.5M parameters vs. EfficientNet-B0 (5.3M), ResNet-50 (25.6M), or ViT-Base (86M)
• Originally designed for mobile and edge deployment

📊 Dataset

Property	Value
Source	microsoft/cats_vs_dogs
Total Images	23,262
Train Split	18,609 (80%)
Validation Split	4,653 (20%)
Split Strategy	Stratified by class, seed=42
Classes	Cat (0), Dog (1)
Class Balance	~50/50 (balanced)

🏋️ Training Steps

Step 1: Dataset Preparation

• Load microsoft/cats_vs_dogs from HuggingFace Datasets
• Manual 80/20 stratified train/validation split (dataset only has a single train split)
• Verify class balance: ~50% cats, ~50% dogs in both splits

Step 2: Model Initialization

• Load pretrained MobileNetV2 from google/mobilenet_v2_1.0_224 (ImageNet-1K weights)
• Replace 1000-class classification head → 2-class head (cat/dog)
• ignore_mismatched_sizes=True handles the head swap automatically

Step 3: Data Augmentation & Preprocessing

Training transforms:

• RandomResizedCrop(224, scale=(0.8, 1.0)) — random crop with scale augmentation
• RandomHorizontalFlip(p=0.5) — mirror augmentation
• ColorJitter(brightness=0.2, contrast=0.2, saturation=0.2, hue=0.1) — color augmentation
• Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]) — ImageNet normalization

Validation transforms:

• Resize(256) → CenterCrop(224) — deterministic center crop
• Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])

Step 4: Training Configuration

Hyperparameter	Value
Optimizer	AdamW
Learning Rate	2e-4
LR Scheduler	Cosine with warmup (10%)
Weight Decay	1e-4
Epochs	10
Batch Size	32
Mixed Precision	FP16
Metric	Accuracy (best model selected)

Step 5: Training Execution

• Fine-tune all layers (no frozen backbone)
• Evaluate after every epoch
• Save best model based on validation accuracy
• Push final model to HuggingFace Hub

Step 6: Evaluation & Visualization

• Compute final validation accuracy and loss
• Generate training loss vs validation loss curves
• Generate validation accuracy curve with 85% target line

📈 Training Curves

🔬 How to Use

from transformers import pipeline

classifier = pipeline("image-classification", model="DsJASPREET/mobilenetv2-cats-dogs-classifier")
result = classifier("path/to/cat_or_dog.jpg")
print(result)
# [{'label': 'cat', 'score': 0.98}, {'label': 'dog', 'score': 0.02}]

Or with manual preprocessing:

from transformers import AutoImageProcessor, AutoModelForImageClassification
from PIL import Image
import torch

processor = AutoImageProcessor.from_pretrained("DsJASPREET/mobilenetv2-cats-dogs-classifier")
model = AutoModelForImageClassification.from_pretrained("DsJASPREET/mobilenetv2-cats-dogs-classifier")

image = Image.open("cat.jpg")
inputs = processor(image, return_tensors="pt")

with torch.no_grad():
    logits = model(**inputs).logits
    
predicted_class = logits.argmax(-1).item()
print(model.config.id2label[predicted_class])  # "cat" or "dog"

📑 Reference Papers

Paper	Venue	Link	Relevance
MobileNetV2: Inverted Residuals and Linear Bottlenecks	CVPR 2018	arxiv:1801.04381	Base architecture — inverted residual blocks + depthwise separable convolutions
EfficientNet: Rethinking Model Scaling for CNNs	ICML 2019	arxiv:1905.11946	Compound scaling reference — larger but more accurate alternative
Cross-Dataset Generalization of Mobile CNN Architectures	2024	arxiv:2511.00335	Benchmarked 11 mobile architectures; MobileNetV2 ranked 3rd in cross-dataset generalization
MobileNetV3: Searching for MobileNetV3	ICCV 2019	arxiv:1905.02244	Successor with hardware-aware NAS; better accuracy but larger

🏗️ Architecture Details

MobileNetV2 Architecture:
├── Conv2d (3→32, stride=2)           # Initial convolution
├── InvertedResidual ×1  (32→16)      # Bottleneck block 1
├── InvertedResidual ×2  (16→24)      # Bottleneck block 2  
├── InvertedResidual ×3  (24→32)      # Bottleneck block 3
├── InvertedResidual ×4  (32→64)      # Bottleneck block 4
├── InvertedResidual ×3  (64→96)      # Bottleneck block 5
├── InvertedResidual ×3  (96→160)     # Bottleneck block 6
├── InvertedResidual ×1  (160→320)    # Bottleneck block 7
├── Conv2d (320→1280)                 # Feature extraction
├── AdaptiveAvgPool2d                 # Global pooling
├── Dropout(0.2)                      # Regularization
└── Linear (1280→2)                   # Classification head (cat/dog)

Key Innovation — Inverted Residual Block:

Input → 1×1 Conv (expand) → 3×3 Depthwise Conv → 1×1 Conv (project) → + Input
         ↑ expansion ratio                              ↑ linear bottleneck

🎯 Training Space

Train and try the model interactively: DsJASPREET/train-cats-dogs-classifier

License

Apache 2.0