convnets.py

"""
CNN models for binary and multi-class classifications
"""
import torch
from torch import nn


class Convnet(nn.Module):
    """
    Convolutional Neural Network for binary classification

    input args: n_classes (int) --> number of classes

    Input shape: [1, 60, 60]
    
    Matrix shape (Conv layer):

    Input shape: [N, C_in, H, W]
        - N: batch_size
        - C_in: number of input channels
        - H: height of input planes
        - W: width of input planes

    - Conv2d(1, 64, (5, 3), 1) --> [64, 56, 58]
    - MaxPool2d(kernel_size=(2, 1)) --> [64, 28, 58]
    - Conv2d(64, 128, (5, 3), 1) --> [128, 24, 56]
    - MaxPool2d(kernel_size=(2, 1)) --> [128, 12, 56]
    - Conv2d(128, 256, (5, 3), 1) --> [256, 8, 54]
    - MaxPool2d(kernel_size=(2, 1)) --> [256, 4, 54]
    
    Matrix shape (Fully connected layer):
    - Linear(256 * 4 * 54, 1024) --> [1024]
    - Linear(1024, 512) --> [512]
    - Linear(512, 128) --> [128]
    - Linear(128, 64) --> [64]
    - Linear(64, n_classes) --> [n_classes]

    Softmax() --> to probability
    """
    def __init__(self, n_classes: int) -> None:
        super().__init__()
        self.cnn = nn.Sequential(
            nn.Conv2d(in_channels=1, out_channels=64, kernel_size=(5, 3), stride=1),
            nn.BatchNorm2d(64),
            nn.LeakyReLU(negative_slope=0.01),
            nn.MaxPool2d(kernel_size=(2, 1)),
            nn.Conv2d(64, 128, (5, 3), 1),
            nn.BatchNorm2d(128),
            nn.LeakyReLU(negative_slope=0.01),
            nn.MaxPool2d(kernel_size=(2, 1)),
            nn.Conv2d(128, 256, (5, 3), 1),
            nn.BatchNorm2d(256),
            nn.LeakyReLU(negative_slope=0.01),
            nn.MaxPool2d(kernel_size=(2, 1)),
        )
        self.dropout = nn.Sequential(nn.Dropout(0.5))
        self.fc = nn.Sequential(
            nn.Linear(256 * 4 * 54, 1024),
            nn.Linear(1024, 512),
            nn.Linear(512, 128),
            nn.Linear(128, 64),
            nn.Linear(64, n_classes),
            nn.Softmax()
        )
        for layer in self.cnn:
            if isinstance(layer, nn.Conv2d):
                nn.init.xavier_normal_(layer.weight)
                nn.init.constant_(layer.bias, 0.0)


    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """
        forward prop
        """
        x = self.cnn(x)
        x = self.dropout(x)
        x = x.view(x.size(0), -1)
        x = self.fc(x)
        return x