Block Compressed Row Storage Format

# %%
import numpy as np
from scipy import sparse
# https://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.bsr_array.html#scipy.sparse.bsr_array

# %%
A = np.array([[1., 0., 0., 0., 0., 0., 0., 0.],
...        [3., 5., 0., 0., 0., 0., 0., 0.],
...        [0., 0., 0., 1., 0., 0., 0., 0.],
...        [0., 0., 2., 0., 0., 0., 0., 0.],
...        [0., 0., 5., 2., 0., 1., 0., 0.],
...        [2., 0., 0., 0., 0., 0., 0., 0.],
...        [0., 0., 0., 4., 0., 0., 3., 1.],
...        [0., 0., 0., 5., 0., 0., 0., 2.]])

# %%
m = sparse.bsr_array(A, blocksize=(4,4))

# %%
m.data # corresponding block values are stored in data[ indptr[i]: indptr[i+1] ]

# %%
# column index, different to paper
m.indices #  block column indices for row i are stored in indices[indptr[i]:indptr[i+1]]

# %%
# row pointer
m.indptr # BSR format index pointer array

# %%
#m2by2 = sparse.bsr_array(A, blocksize=(2,2))
#print(m2by2.data)
#print(m2by2.indices)
#print(m2by2.indptr)