def RS(S, second_pass=False):
"""Compute a C/F splitting using Ruge-Stuben coarsening
Parameters
----------
S : csr_matrix
Strength of connection matrix indicating the strength between nodes i
and j (S_ij)
second_pass : bool, default False
Perform second pass of classical AMG coarsening. Can be important for
classical AMG interpolation. Typically not done in parallel (e.g. Hypre).
Returns
-------
splitting : ndarray
Array of length of S of ones (coarse) and zeros (fine)
Examples
--------
>>> from pyamg.gallery import poisson
>>> from pyamg.classical import RS
>>> S = poisson((7,), format='csr') # 1D mesh with 7 vertices
>>> splitting = RS(S)
See Also
--------
amg_core.rs_cf_splitting
References
----------
.. [1] Ruge JW, Stuben K. "Algebraic multigrid (AMG)"
In Multigrid Methods, McCormick SF (ed.),
Frontiers in Applied Mathematics, vol. 3.
SIAM: Philadelphia, PA, 1987; 73-130.
"""
if not isspmatrix_csr(S):
raise TypeError('expected csr_matrix')
S = remove_diagonal(S)
T = S.T.tocsr() # transpose S for efficient column access
splitting = np.empty(S.shape[0], dtype='intc')
influence = np.zeros((S.shape[0],), dtype='intc')
amg_core.rs_cf_splitting(S.shape[0],
S.indptr, S.indices,
T.indptr, T.indices,
influence,
splitting)
if second_pass:
amg_core.rs_cf_splitting_pass2(S.shape[0], S.indptr,
S.indices, splitting)
return splitting
def RS(S, second_pass=False):
"""Compute a C/F splitting using Ruge-Stuben coarsening
Parameters
----------
S : csr_matrix
Strength of connection matrix indicating the strength between nodes i
and j (S_ij)
second_pass : bool, default False
Perform second pass of classical AMG coarsening. Can be important for
classical AMG interpolation. Typically not done in parallel (e.g. Hypre).
Returns
-------
splitting : ndarray
Array of length of S of ones (coarse) and zeros (fine)
Examples
--------
>>> from pyamg.gallery import poisson
>>> from pyamg.classical import RS
>>> S = poisson((7,), format='csr') # 1D mesh with 7 vertices
>>> splitting = RS(S)
See Also
--------
amg_core.rs_cf_splitting
References
----------
.. [1] Ruge JW, Stuben K. "Algebraic multigrid (AMG)"
In Multigrid Methods, McCormick SF (ed.),
Frontiers in Applied Mathematics, vol. 3.
SIAM: Philadelphia, PA, 1987; 73-130.
"""
if not isspmatrix_csr(S):
raise TypeError('expected csr_matrix')
S = remove_diagonal(S)
T = S.T.tocsr() # transpose S for efficient column access
splitting = np.empty(S.shape[0], dtype='intc')
influence = np.zeros((S.shape[0],), dtype='intc')
amg_core.rs_cf_splitting(S.shape[0],
S.indptr, S.indices,
T.indptr, T.indices,
influence,
splitting)
if second_pass:
amg_core.rs_cf_splitting_pass2(S.shape[0], S.indptr,
S.indices, splitting)
return splitting
