Source code for cil.optimisation.functions.OperatorCompositionFunction
# Copyright 2019 United Kingdom Research and Innovation
# Copyright 2019 The 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.
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# Authors:
# CIL Developers, listed at: https://github.com/TomographicImaging/CIL/blob/master/NOTICE.txt
from cil.optimisation.functions import Function
from cil.optimisation.operators import Operator, ScaledOperator
import warnings
[docs]
class OperatorCompositionFunction(Function):
""" Composition of a function with an operator as : :math:`(F \otimes A)(x) = F(Ax)`
:parameter function: :code:`Function` F
:parameter operator: :code:`Operator` A
For general operator, we have no explicit formulas for convex_conjugate,
proximal and proximal_conjugate
"""
def __init__(self, function, operator):
'''creator
:param A: operator
:type A: :code:`Operator`
:param f: function
:type f: :code:`Function`
'''
super(OperatorCompositionFunction, self).__init__()
self.function = function
self.operator = operator
@property
def L(self):
if self._L is None:
try:
self._L = self.function.L * (self.operator.norm() ** 2)
except ValueError as ve:
self._L = None
return self._L
def __call__(self, x):
""" Returns :math:`F(Ax)`
"""
return self.function(self.operator.direct(x))
[docs]
def gradient(self, x, out=None):
""" Return the gradient of F(Ax),
..math :: (F(Ax))' = A^{T}F'(Ax)
"""
tmp = self.operator.range_geometry().allocate()
self.operator.direct(x, out=tmp)
self.function.gradient(tmp, out=tmp)
return self.operator.adjoint(tmp, out=out)