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preconditioner.py
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preconditioner.py
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#!/usr/bin/env python3
## vi: tabstop=4 shiftwidth=4 softtabstop=4 expandtab
## ---------------------------------------------------------------------
##
## Copyright (C) 2018 by the adcc authors
##
## This file is part of adcc.
##
## adcc is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published
## by the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## adcc is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with adcc. If not, see <http://www.gnu.org/licenses/>.
##
## ---------------------------------------------------------------------
import numpy as np
from adcc.AdcMatrix import AdcMatrixlike
from adcc.AmplitudeVector import AmplitudeVector
class PreconditionerIdentity:
"""
Preconditioner, which does absolutely nothing
"""
def apply(self, invecs):
return invecs
def __matmul__(self, x):
return x
class JacobiPreconditioner:
"""
Jacobi-type preconditioner
Represents the application of (D - σ I)^{-1}, where
D is the diagonal of the adcmatrix.
"""
def __init__(self, adcmatrix, shifts=0.0):
if not isinstance(adcmatrix, AdcMatrixlike):
raise TypeError("Only an AdcMatrixlike may be used with this "
"preconditioner for now.")
self.diagonal = adcmatrix.diagonal()
self.shifts = shifts
def update_shifts(self, shifts):
"""
Update the shift value or values applied to the diagonal.
If this is a single value it will be applied to all
vectors simultaneously. If it is multiple values,
then each value will be applied only to one
of the passed vectors.
"""
self.shifts = shifts
def apply(self, invecs):
if isinstance(invecs, AmplitudeVector):
if not isinstance(self.shifts, (float, np.number)):
raise TypeError("Can only apply JacobiPreconditioner "
"to a single vector if shifts is "
"only a single number.")
return invecs / (self.diagonal - self.shifts)
elif isinstance(invecs, list):
if len(self.shifts) != len(invecs):
raise ValueError("Number of vectors passed does not agree "
"with number of shifts stored inside "
"precoditioner. Update using the "
"'update_shifts' method.")
return [v / (self.diagonal - self.shifts[i])
for i, v in enumerate(invecs)]
else:
raise TypeError("Input type not understood: " + str(type(invecs)))
def __matmul__(self, invecs):
return self.apply(invecs)
# __matvec__