请帮我用pytorch写出SparseAttention的代码
时间: 2024-02-11 08:09:23 浏览: 16
好的,以下是一个使用pytorch实现SparseAttention的简单代码示例:
```python
import torch
import torch.nn.functional as F
from torch import nn
class SparseAttention(nn.Module):
def __init__(self, in_features, out_features, k):
super(SparseAttention, self).__init__()
self.in_features = in_features
self.out_features = out_features
self.k = k
self.query = nn.Linear(in_features, out_features)
self.key = nn.Linear(in_features, out_features)
self.value = nn.Linear(in_features, out_features)
def forward(self, x):
batch_size, seq_len, _ = x.size()
query = self.query(x)
key = self.key(x)
value = self.value(x)
# 使用k-means选择与当前位置最相关的k个输入元素
kmeans = nn.KMeans(self.k, max_iter=100)
key_flat = key.view(batch_size * seq_len, self.out_features)
centroids = kmeans(key_flat)[0]
centroids = centroids.view(batch_size, seq_len, self.k, self.out_features)
# 计算注意力权重
query = query.unsqueeze(2).expand(batch_size, seq_len, self.k, self.out_features)
attn_weights = (query * centroids).sum(dim=-1) / self.out_features ** 0.5
attn_weights = F.softmax(attn_weights, dim=2)
# 使用注意力权重加权求和得到输出
value = value.unsqueeze(2).expand(batch_size, seq_len, self.k, self.out_features)
attn_output = (value * attn_weights.unsqueeze(-1)).sum(dim=2)
return attn_output
```
在这个例子中,我们定义了一个SparseAttention类,它包含了query、key和value三个线性层,分别用于计算注意力中的查询、键和值。在forward函数中,我们先计算出所有的query、key和value,然后使用KMeans算法选择与当前位置最相关的k个输入元素,并计算注意力权重。最后,我们使用注意力权重加权求和得到输出。