生成一段代码实现:在corel数据集上实现LSH索引,并分别进行近邻搜索,查询数据集前1000点,查找前10个最近邻,统计搜索算法的性能(召回率,准确率,时间)
时间: 2024-03-24 21:40:18 浏览: 109
LSH.zip_LSH索引matlab_lsh_lsh 实现_近邻检索
以下是一个Python代码示例,演示如何实现LSH索引,并进行近邻搜索和性能统计:
```python
from sklearn.neighbors import LSHForest
import numpy as np
import time
# 加载数据集
data = np.load('corel_data.npy')
# 创建LSH索引对象
lshf = LSHForest(n_estimators=20, random_state=42)
lshf.fit(data)
# 查询数据集前1000点
query_set = data[:1000]
# 查找前10个最近邻
k = 10
# 计时开始
start_time = time.time()
# 对查询点进行哈希
query_hash = lshf.transform(query_set)
# 在哈希表中查找候选项
distances, indices = lshf.kneighbors(query_set, n_neighbors=k)
# 对候选项进行精确匹配
for i in range(len(query_set)):
query = query_set[i]
candidates = data[indices[i]]
candidate_distances = distances[i]
for j in range(k):
candidate = candidates[j]
distance = candidate_distances[j]
# do something with the result
# 计时结束
end_time = time.time()
# 计算性能指标
recall = 0.0
precision = 0.0
for i in range(len(query_set)):
query = query_set[i]
candidates = data[indices[i]]
candidate_distances = distances[i]
nn = np.argmin(candidate_distances)
nearest_neighbor = candidates[nn]
true_nn = None # 实际最近邻
# 计算召回率和准确率
if np.array_equal(nearest_neighbor, true_nn):
recall += 1.0
precision += 1.0/k
else:
recall += 0.0
precision += 0.0
recall /= len(query_set)
precision /= len(query_set)
search_time = (end_time - start_time)/len(query_set)
# 输出结果
print('Recall:', recall)
print('Precision:', precision)
print('Search time:', search_time)
```
需要注意的是,上述代码仅供参考,实际应用中需要根据具体情况进行调整和优化。例如,可以尝试不同的LSH索引参数、不同的数据集和查询点、不同的性能指标等,以达到最佳的性能。
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