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#-------------------------------------------------------------------------------
# SPEX/Python/SPEXpy/spex_from_matrix_file.py: read matrix from file
#-------------------------------------------------------------------------------
# SPEX: (c) 2022-2024, Christopher Lourenco, Jinhao Chen,
# Lorena Mejia Domenzain, Erick Moreno-Centeno, and Timothy A. Davis.
# All Rights Reserved.
# SPDX-License-Identifier: GPL-2.0-or-later or LGPL-3.0-or-later
#------------------------------------------------------------------------------
import numpy as np
from scipy.sparse import coo_matrix
def spex_matrix_from_file(fname):
#fname is the name of the file that contains matrix A
##--------------------------------------------------------------------------
## Load file data and store it in mat
##--------------------------------------------------------------------------
mat = np.loadtxt(fname, delimiter=' ')
##--------------------------------------------------------------------------
## Splice mat to get the componets of matrix A and populate a scipy sparse matrix
##--------------------------------------------------------------------------
data = mat[1:,2]
row = mat[1:,0].astype(int)
col = mat[1:,1].astype(int)
n = mat[0][0].astype(int)
m = mat[0][1].astype(int)
## The matrix in the file is in triplet form
triplet=coo_matrix((data, (row, col)),shape=(n, m))
## Change the triplet matrix into a csc matrix
A = triplet.tocsc()
return A
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