---
tags: machine-learning
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# VggNet: Summary and Implementation

<div style="text-align: center">
<img src="https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/0.png?token=AMAXSKN5KOX7F6TA34Z4K226WMHKI">
</div>

>This post is divided into 2 sections: Summary and Implementation.
>
>We are going to have an in-depth review of [Very Deep Convolutional Networks for Large-Scale Image Recognition][paper] paper which introduces the VggNet architecture.
>
> The implementation uses Pytorch as framework. To see full implementation,
> please refer to this [repository].
>
> Also, if you want to read other "Summary and Implementation", feel free to
> check them at my [blog](https://ferdinandmom.engineer/deep-learning/).
>
# I) Summary

- The paper [Very Deep Convolutional Networks for Large-Scale Image Recognition][paper] introduces a familly of ConvNets called VGGNet.
- During ILSVLC-2014, they achieved 2nd place at the classification task (top-5 test error = 7.32%)
- They demonstrated that depth is beneficial for the classification accuracy.
- In spite of its large depth, the number of weights is not greater than number of weights in a more shallow net with larger conv.
- VGGNet uses a smaller receptive field (3x3 stride 1) contrary to AlexNet (11x11 with stride 4) and ZFNet (7x7 stride 2).

---

VGG architecture:

- Input size 224x224x3 (RGB image).
- Preprocessing done by substracting training set RGB mean.
- Filters size 3x3.
- Convolutional layers:
- stride 1.
- padding 1 (3x3 conv layers).
- ReLU or LRN for one of the config.
- followed by 5 max pooling layers (not all of them).
- 2x2 window.
- stride = 2.
- Fully-connected layers:
- 1st: 4096 (ReLU).
- 2nd: 4096 (ReLU).
- 3rd: 100 (Softmax).

VGGNet configurations:

- VGG-11
- VGG-11 (LRN)
- VGG-13
- VGG-16 (Conv1)
- VGG-16
- VGG-19

<div style="text-align: center">
<img src="https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/1.png?token=AMAXSKPJWDG6HR7HYB72KCS6WMHKI">
</div>

<br>

We are going to focus on VGG-16. Here is its architecture:

<br>

<div style="text-align: center">
<img src="https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/2.png?token=AMAXSKN3R2EKTD235XSBT2C6WMHKM">
</div>

<div style="text-align: center">
<img src="https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/3.png?token=AMAXSKLO7B2XISQS7FH54C26WMHKK">
</div>

<div style="text-align: center">
<img src="https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/4.png?token=AMAXSKN5R3RI33N2IPYS5426WMHKM">
</div>

# II) Implementation

We are going to implement VGG-16.

### 1) Architecture build

class Vgg16(nn.Module):
    
    def __init__(self):
        super(Vgg16, self).__init__()
        
        # CONV PART.
        self.features = nn.Sequential(OrderedDict([
            ('block1-conv1', nn.Conv2d(3, 64, kernel_size=3, stride=1, padding=1)),
            ('block1-act1', nn.ReLU()),
            ('block1-conv2', nn.Conv2d(64, 64, kernel_size=3, stride=1, padding=1)),
            ('block1-act2', nn.ReLU()),
            
            ('pool1', nn.MaxPool2d(kernel_size=2, stride=2)),
            
            ('block2-conv1', nn.Conv2d(64, 128, kernel_size=3, stride=1, padding=1)),
            ('block2-act1', nn.ReLU()),
            ('block2-conv2', nn.Conv2d(128, 128, kernel_size=3, stride=1, padding=1)),
            ('block2-act2', nn.ReLU()),
            
            ('pool2', nn.MaxPool2d(kernel_size=2, stride=2)),
            
            ('block3-conv1', nn.Conv2d(128, 256, kernel_size=3, stride=1, padding=1)),
            ('block3-act1', nn.ReLU()),
            ('block3-conv2', nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1)),
            ('block3-act2', nn.ReLU()),
            ('block3-conv3', nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1)),
            ('block3-act3', nn.ReLU()),
            
            ('pool3', nn.MaxPool2d(kernel_size=2, stride=2)),
            
            ('block4-conv1', nn.Conv2d(256, 512, kernel_size=3, stride=1, padding=1)),
            ('block4-act1', nn.ReLU()),
            ('block4-conv2', nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1)),
            ('block4-act2', nn.ReLU()),
            ('block4-conv3', nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1)),
            ('block4-act3', nn.ReLU()),
            
            ('pool4', nn.MaxPool2d(kernel_size=2, stride=2)),
            
            ('block5-conv1', nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1)),
            ('block5-act1', nn.ReLU()),
            ('block5-conv2', nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1)),
            ('block5-act2', nn.ReLU()),
            ('block5-conv3', nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1)),
            ('block5-act3', nn.ReLU()),
            
            ('pool5', nn.MaxPool2d(kernel_size=2, stride=2))
        ]))
        
        # FC PART.
        
        self.classifier = nn.Sequential(OrderedDict([
            ('fc6', nn.Linear(512 * 7 * 7, 4096)),
            ('act6', nn.ReLU()),
            ('fc7', nn.Linear(4096, 4096)),
            ('act7', nn.ReLU()),
            ('fc8', nn.Linear(4096, 1000))
        ]))
        
        
    def forward(self, x):
        x = self.features(x)
        x = x.view(x.size(0), -1)
        x = self.classifier(x)
        return x

### 2) Evaluating

fig2 = plt.figure(figsize=(30,10))

model.eval()
with torch.no_grad():
    
    for i, image in enumerate(test_loader):
        probs = torch.nn.Softmax(dim=-1)(model(image))
        
        probability, class_idx = torch.max(probs, 1)
        class_name = class_names[class_idx]
         
        fig2.add_subplot(1,4,i+1)
        plt.imshow(cv2.cvtColor(custom_dataset.imgsToDisplay[i], cv2.COLOR_BGR2RGB))
        plt.title("Class: " + class_name + ", probability: %.4f" % probability, fontsize=13)
        plt.axis('off')

        plt.text(0, 240, 'Top-5 Accuracy:')
        x, y = 10, 260
        
        for idx in np.argsort(probs.numpy())[0][-5::][::-1]:
            s = '- {}, probability: {:.4f}'.format(class_names[idx], probs[0, idx])
            plt.text(x, y, s=s, fontsize=10)
            y += 20
        print()

![evaluating-image]

[paper]:https://arxiv.org/pdf/1409.1556.pdf
[repository]: https://github.com/3outeille/Research-Paper-Summary/tree/master/src/architecture/vgg/pytorch
[evaluating-image]: https://raw.githubusercontent.com/valoxe/image-storage-1/master/research-paper-summary/vggnet/5.png?token=AMAXSKKRZ6FERMROIFH5ROS6WMHKM