brosnet/model.py

"""Char-CNN classifier."""

import torch
import torch.nn as nn
import torch.nn.functional as F

from brosnet.dataset import VOCAB_SIZE


class BrosNet(nn.Module):
    def __init__(
        self,
        vocab_size: int = VOCAB_SIZE,
        embed_dim: int = 32,
        num_filters: int = 64,
        kernel_sizes: tuple[int, ...] = (2, 3, 4, 5),
        hidden_dim: int = 128,
        num_classes: int = 5,
        dropout: float = 0.3,
        max_len: int = 512,
    ):
        super().__init__()
        self.max_len = max_len
        self.embedding = nn.Embedding(vocab_size, embed_dim, padding_idx=0)
        self.convs = nn.ModuleList(
            [
                nn.Conv1d(embed_dim, num_filters, kernel_size=k)
                for k in kernel_sizes
            ]
        )
        conv_out = num_filters * len(kernel_sizes)
        self.fc1 = nn.Linear(conv_out, hidden_dim)
        self.dropout = nn.Dropout(dropout)
        self.fc2 = nn.Linear(hidden_dim, num_classes)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        # x: (batch, seq_len)
        emb = self.embedding(x)  # (batch, seq, embed)
        emb = emb.transpose(1, 2)  # (batch, embed, seq)
        pooled = []
        for conv in self.convs:
            h = F.relu(conv(emb))
            p = F.adaptive_max_pool1d(h, 1).squeeze(-1)
            pooled.append(p)
        cat = torch.cat(pooled, dim=1)
        h = F.relu(self.fc1(cat))
        h = self.dropout(h)
        return self.fc2(h)