
import numpy as np
from scipy.sparse import csr_matrix

dense_a = np.arange(16).reshape(4,4)
dense_b = np.arange(16).reshape(4,4)
np.fill_diagonal(dense_a, 0)
np.fill_diagonal(dense_b, 0)
print(dense_a)
print(dense_a*dense_b)
print(dense_a@dense_b.T)
print(np.dot(dense_a, dense_b.T))

sparse_a = csr_matrix(dense_a)
sparse_b = csr_matrix(dense_b)
sparse_rez1 = sparse_a.multiply(sparse_a)
sparse_rez2 = sparse_a.dot(sparse_b.T)
print(sparse_rez1.todense())
print(csr_matrix.toarray(sparse_rez2))

[[ 0  1  2  3]
 [ 4  0  6  7]
 [ 8  9  0 11]
 [12 13 14  0]]
[[  0   1   4   9]
 [ 16   0  36  49]
 [ 64  81   0 121]
 [144 169 196   0]]
[[ 14  33  42  41]
 [ 33 101 109 132]
 [ 42 109 266 213]
 [ 41 132 213 509]]
[[ 14  33  42  41]
 [ 33 101 109 132]
 [ 42 109 266 213]
 [ 41 132 213 509]]
[[  0   1   4   9]
 [ 16   0  36  49]
 [ 64  81   0 121]
 [144 169 196   0]]
[[ 14  33  42  41]
 [ 33 101 109 132]
 [ 42 109 266 213]
 [ 41 132 213 509]]

Operations with sparse matrices¶