Let's work this out in a step by step way to be sure we have the right answer 对上述代码仔细分析
时间: 2024-03-06 08:46:25 浏览: 14
好的,让我们逐步分析上述代码:
1. 首先,在MHAlayer类的初始化函数中,定义了一些变量和层:
```
def __init__(self, n_heads, cat, input_dim, hidden_dim, attn_dropout=0.1, dropout=0):
super(MHAlayer, self).__init__()
self.n_heads = n_heads
self.input_dim = input_dim
self.hidden_dim = hidden_dim
self.head_dim = self.hidden_dim / self.n_heads
self.dropout = nn.Dropout(attn_dropout)
self.dropout1 = nn.Dropout(dropout)
self.norm = 1 / math.sqrt(self.head_dim)
self.w = nn.Linear(input_dim * cat, hidden_dim, bias=False)
self.k = nn.Linear(input_dim, hidden_dim, bias=False)
self.v = nn.Linear(input_dim, hidden_dim, bias=False)
self.fc = nn.Linear(hidden_dim, hidden_dim, bias=False)
```
其中,n_heads表示头的数量,cat表示输入的拼接层的数量,input_dim表示输入维度,hidden_dim表示隐藏层维度,attn_dropout表示Attention层的dropout率,dropout表示全连接层的dropout率。head_dim是每个头的维度,是hidden_dim和n_heads的商,norm是归一化因子。w、k、v、fc分别是线性变换层,其中w接收的是输入拼接层的输出,k和v接收的是context的输出,fc是输出层。
2. 接着,在forward函数中,对输入数据进行处理:
```
def forward(self, state_t, context, mask):
batch_size, n_nodes, input_dim = context.size()
Q = self.w(state_t).view(batch_size, 1, self.n_heads, -1)
K = self.k(context).view(batch_size, n_nodes, self.n_heads, -1)
V = self.v(context).view(batch_size, n_nodes, self.n_heads, -1)
Q, K, V = Q.transpose(1, 2), K.transpose(1, 2), V.transpose(1, 2)
```
其中,state_t是输入拼接层的输出,context是输入的张量,mask是需要Attention的节点。首先计算查询向量Q,键向量K和值向量V,并将它们的维度变为(batch_size, n_heads, hidden_dim),然后将Q、K、V分别转置维度。
3. 接下来,计算Attention得分:
```
compatibility = self.norm * torch.matmul(Q, K.transpose(2, 3))
compatibility = compatibility.squeeze(2)
mask = mask.unsqueeze(1).expand_as(compatibility)
u_i = compatibility.masked_fill(mask.bool(), float("-inf"))
scores = F.softmax(u_i, dim=-1)
scores = scores.unsqueeze(2)
```
首先,计算Q和K的点积,再除以sqrt(head_dim)得到compatibility,然后将compatibility的第2个维度去掉,即(batch_size, n_heads, n_nodes),接着,根据mask将需要Attention的节点的得分设置为负无穷,最后进行softmax操作得到Attention的权重scores。
4. 根据得分加权求和得到Attention的输出:
```
out_put = torch.matmul(scores, V)
out_put = out_put.squeeze(2).view(batch_size, self.hidden_dim)
out_put = self.fc(out_put)
return out_put
```
将得分scores与值向量V相乘,并将第2个维度去掉,即(batch_size, n_nodes, hidden_dim),然后再通过一个线性层进行维度转换,最终输出结果。
总的来说,这个MHAlayer模块实现了Multi-Head Attention机制,用于文本序列处理中的Attention机制。它将查询向量、键向量和值向量映射到hidden_dim维度,并将它们分成n_heads份,计算Attention得分,再根据得分加权求和得到Attention的输出。