def reverse_cuthill_mckee(A, sym=False):
"""
Returns the permutation array that orders a sparse CSR or CSC matrix
in Reverse-Cuthill McKee ordering. Since the input matrix must be
symmetric, this routine works on the matrix A+Trans(A) if the sym flag is
set to False (Default).
It is assumed by default (*sym=False*) that the input matrix is not
symmetric. This is because it is faster to do A+Trans(A) than it is to
check for symmetry for a generic matrix. If you are guaranteed that the
matrix is symmetric in structure (values of matrix element do not matter)
then set *sym=True*
Parameters
----------
A : csc_matrix, csr_matrix
Input sparse CSC or CSR sparse matrix format.
sym : bool {False, True}
Flag to set whether input matrix is symmetric.
Returns
-------
perm : array
Array of permuted row and column indices.
Notes
-----
This routine is used primarily for internal reordering of Lindblad
superoperators for use in iterative solver routines.
References
----------
E. Cuthill and J. McKee, "Reducing the Bandwidth of Sparse Symmetric
Matrices", ACM '69 Proceedings of the 1969 24th national conference,
(1969).
"""
if not (sp.isspmatrix_csc(A) or sp.isspmatrix_csr(A)):
raise TypeError('Input must be CSC or CSR sparse matrix.')
nrows = A.shape[0]
if not sym:
A = A + A.transpose()
return _reverse_cuthill_mckee(A.indices, A.indptr, nrows)
def reverse_cuthill_mckee(A, sym=False):
"""
Returns the permutation array that orders a sparse CSR or CSC matrix
in Reverse-Cuthill McKee ordering. Since the input matrix must be
symmetric, this routine works on the matrix A+Trans(A) if the sym flag is
set to False (Default).
It is assumed by default (*sym=False*) that the input matrix is not
symmetric. This is because it is faster to do A+Trans(A) than it is to
check for symmetry for a generic matrix. If you are guaranteed that the
matrix is symmetric in structure (values of matrix element do not matter)
then set *sym=True*
Parameters
----------
A : csc_matrix, csr_matrix
Input sparse CSC or CSR sparse matrix format.
sym : bool {False, True}
Flag to set whether input matrix is symmetric.
Returns
-------
perm : array
Array of permuted row and column indices.
Notes
-----
This routine is used primarily for internal reordering of Lindblad
superoperators for use in iterative solver routines.
References
----------
E. Cuthill and J. McKee, "Reducing the Bandwidth of Sparse Symmetric
Matrices", ACM '69 Proceedings of the 1969 24th national conference,
(1969).
"""
if not (sp.isspmatrix_csc(A) or sp.isspmatrix_csr(A)):
raise TypeError('Input must be CSC or CSR sparse matrix.')
nrows = A.shape[0]
if not sym:
A = A + A.transpose()
return _reverse_cuthill_mckee(A.indices, A.indptr, nrows)