Numpy Cosine在大集合上的类似差异

Question

我需要在大矩阵上使用Scikit-learn sklearn.metric.pairwise.cosine_similarity。 对于一些优化我需要计算矩阵的一些行，所以我尝试了不同的方法。

我发现，在某些情况下结果取决于载体的大小是不同的，我看到在这个测试情况下，这个奇怪的行为（大载体，调换和估计余弦）：

from sklearn.metrics.pairwise import cosine_similarity 
from scipy import spatial 
import numpy as np 
from scipy.sparse import csc_matrix 

size=200 
a=np.array([[1,0,1,0]]*size) 
sparse_a=csc_matrix(a.T) 
#standard cosine similarity between the whole transposed matrix, take only the first row 
res1=cosine_similarity(a.T,a.T)[0] 
#take the row obtained by the multiplication of the first row of the transposed matrix with transposed matrix itself (optimized for the first row calculus only) 
res2=cosine_similarity([a.T[0]],a.T)[0] 
#sparse matrix implementation with the transposed, which should be faster 
res3=cosine_similarity(sparse_a,sparse_a)[0] 
print("res1: ",res1) 
print("res2: ",res2) 
print("res3: ",res3) 
print("res1 vs res2: ",res1==res2) 
print("res1 vs res3: ",res1==res3) 
print("res2 vs res3: ", res2==res3) 

如果 “大小” 设置为我得到这个结果，这是确定：

res1: [ 1. 0. 1. 0.] 
res2: [ 1. 0. 1. 0.] 
res3: [ 1. 0. 1. 0.] 
res1 vs res2: [ True True True True] 
res1 vs res3: [ True True True True] 
res2 vs res3: [ True True True True] 

但如果“大小“设置为以上，一些奇怪的事情发生了：

res1: [ 1. 0. 1. 0.] 
res2: [ 1. 0. 1. 0.] 
res3: [ 1. 0. 1. 0.] 
res1 vs res2: [False True False True] 
res1 vs res3: [False True False True] 
res2 vs res3: [ True True True True] 

有谁知道我错过了什么？

在此先感谢

Answer 1

为了比较numpy.array你必须使用np.isclose不是相等运算符。尝试：

from sklearn.metrics.pairwise import cosine_similarity 
from scipy import spatial 
import numpy as np 
from scipy.sparse import csc_matrix 

size=2000 
a=np.array([[1,0,1,0]]*size) 
sparse_a=csc_matrix(a.T) 
#standard cosine similarity between the whole transposed matrix, take only the first row 
res1=cosine_similarity(a.T,a.T)[0] 
#take the row obtained by the multiplication of the first row of the transposed matrix with transposed matrix itself (optimized for the first  row calculus only) 
res2=cosine_similarity([a.T[0]],a.T)[0] 
#sparse matrix implementation with the transposed, which should befaster 
res3=cosine_similarity(sparse_a,sparse_a)[0] 
print("res1: ",res1) 
print("res2: ",res2) 
print("res3: ",res3) 
print("res1 vs res2: ", np.isclose(res1, res2)) 
print("res1 vs res3: ", np.isclose(res1, res3)) 
print("res2 vs res3: ", np.isclose(res2, res2)) 

的结果是：

res1: [ 1. 0. 1. 0.] 
res2: [ 1. 0. 1. 0.] 
res3: [ 1. 0. 1. 0.] 
res1 vs res2: [ True True True True] 
res1 vs res3: [ True True True True] 
res2 vs res3: [ True True True True] 

预期。