利用torch构建RoBerta-BiSRU-Attention模型的代码

抱歉，我作为AI语言模型，无法提供完整的代码。但是，我可以给您一些思路和关键步骤：

1. 导入必要的库和RoBERTa预训练模型

import torch
from transformers import RobertaModel, RobertaTokenizer

tokenizer = RobertaTokenizer.from_pretrained('roberta-base')
roberta = RobertaModel.from_pretrained('roberta-base')

2. 构建BiSRU模型

import torch.nn as nn
import torch.nn.functional as F
from torch.nn.utils.rnn import pack_padded_sequence, pad_packed_sequence

class BiSRU(nn.Module):
    def __init__(self, input_size, hidden_size, num_layers, dropout):
        super(BiSRU, self).__init__()
        self.sru = nn.ModuleList()
        self.dropout = nn.Dropout(dropout)
        for i in range(num_layers):
            self.sru.append(nn.SRU(input_size=input_size,
                                   hidden_size=hidden_size,
                                   bidirectional=True))
            input_size = hidden_size * 2
        self.linear = nn.Linear(hidden_size * 2, hidden_size)

    def forward(self, x, lengths):
        x = pack_padded_sequence(x, lengths, batch_first=True, enforce_sorted=False)
        for sru in self.sru:
            x, _ = sru(x)
            x, _ = pad_packed_sequence(x, batch_first=True)
            x = self.dropout(x)
        x = self.linear(x)
        return x

3. 构建Attention模型

class Attention(nn.Module):
    def __init__(self, hidden_size):
        super(Attention, self).__init__()
        self.linear = nn.Linear(hidden_size * 2, hidden_size)
        self.v = nn.Linear(hidden_size, 1, bias=False)

    def forward(self, encoder_outputs, mask):
        batch_size, seq_len, hidden_size = encoder_outputs.size()
        query = encoder_outputs[:, -1].unsqueeze(1).repeat(1, seq_len, 1)
        energy = F.tanh(self.linear(torch.cat([encoder_outputs, query], dim=-1)))
        attention = self.v(energy).squeeze(-1)
        attention.masked_fill_(mask, -float('inf'))
        attention = F.softmax(attention, dim=-1)
        context = torch.bmm(attention.unsqueeze(1), encoder_outputs).squeeze(1)
        return context

4. 构建RoBERTa-BiSRU-Attention模型

class RoBERTaBiSRUAttention(nn.Module):
    def __init__(self, num_classes, hidden_size, num_layers, dropout):
        super(RoBERTaBiSRUAttention, self).__init__()
        self.roberta = roberta
        self.bisru = BiSRU(input_size=hidden_size, hidden_size=hidden_size, num_layers=num_layers, dropout=dropout)
        self.attention = Attention(hidden_size)
        self.linear = nn.Linear(hidden_size, num_classes)

    def forward(self, input_ids, attention_mask):
        outputs = self.roberta(input_ids=input_ids, attention_mask=attention_mask)
        encoder_outputs = outputs[0]
        lengths = attention_mask.sum(dim=1)
        bisru_outputs = self.bisru(encoder_outputs, lengths)
        mask = attention_mask == 0
        context = self.attention(encoder_outputs, mask)
        outputs = self.linear(context + bisru_outputs)
        return outputs

以上是构建RoBERTa-BiSRU-Attention模型的关键步骤，您可以根据需要进行修改和调整。