在transformer里面,multihead_attention是核心,原理不再叙述,nn里有nn.MultiheadAttention可以使用,为方便了解原理,手写代码如下
import torch
import torch.nn as nn
class MultiheadAttention(nn.Module):
# n_heads:多头注意力的数量
# hid_dim:每个词输出的向量维度
def __init__(self, hid_dim, n_heads, dropout):
super(MultiheadAttention, self).__init__()
self.hid_dim = hid_dim
self.n_heads = n_heads
# 强制 hid_dim 必须整除 h
assert hid_dim % n_heads == 0
# 定义 W_q 矩阵
self.w_q = nn.Linear(hid_dim, hid_dim)
# 定义 W_k 矩阵
self.w_k = nn.Linear(hid_dim, hid_dim)
# 定义 W_v 矩阵
self.w_v = nn.Linear(hid_dim, hid_dim)
self.fc = nn.Linear(hid_dim, hid_dim)
self.do = nn.Dropout(dropout)
# 缩放
self.scale = torch.sqrt(torch.FloatTensor([hid_dim // n_heads]))
def forward(self, query, key, value, mask=None):
# K: [64,10