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# -*- coding: utf-8 -*-
# CCP in Tomographic Imaging (CCPi) Core Imaging Library (CIL).
# Copyright 2017 UKRI-STFC
# Copyright 2017 University of Manchester
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from numbers import Number
import numpy
class ScaledOperator(object):
'''ScaledOperator
A class to represent the scalar multiplication of an Operator with a scalar.
It holds an operator and a scalar. Basically it returns the multiplication
of the result of direct and adjoint of the operator with the scalar.
For the rest it behaves like the operator it holds.
Args:
operator (Operator): a Operator or LinearOperator
scalar (Number): a scalar multiplier
Example:
The scaled operator behaves like the following:
sop = ScaledOperator(operator, scalar)
sop.direct(x) = scalar * operator.direct(x)
sop.adjoint(x) = scalar * operator.adjoint(x)
sop.norm() = operator.norm()
sop.range_geometry() = operator.range_geometry()
sop.domain_geometry() = operator.domain_geometry()
'''
def __init__(self, operator, scalar):
super(ScaledOperator, self).__init__()
if not isinstance (scalar, Number):
raise TypeError('expected scalar: got {}'.format(type(scalar)))
self.scalar = scalar
self.operator = operator
def direct(self, x, out=None):
if out is None:
return self.scalar * self.operator.direct(x, out=out)
else:
self.operator.direct(x, out=out)
out *= self.scalar
def adjoint(self, x, out=None):
if self.operator.is_linear():
if out is None:
return self.scalar * self.operator.adjoint(x, out=out)
else:
self.operator.adjoint(x, out=out)
out *= self.scalar
else:
raise TypeError('Operator is not linear')
def norm(self, **kwargs):
return numpy.abs(self.scalar) * self.operator.norm(**kwargs)
def range_geometry(self):
return self.operator.range_geometry()
def domain_geometry(self):
return self.operator.domain_geometry()
def is_linear(self):
return self.operator.is_linear()
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