sandwich_operator.py 3.34 KB
Newer Older
Martin Reinecke's avatar
Martin Reinecke committed
1
2
3
4
5
6
7
8
9
10
11
12
13
# This program 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.
#
# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
#
14
# Copyright(C) 2013-2019 Max-Planck-Society
Martin Reinecke's avatar
Martin Reinecke committed
15
#
16
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik.
17

18
import numpy as np
19

20
from .diagonal_operator import DiagonalOperator
Martin Reinecke's avatar
Martin Reinecke committed
21
from .endomorphic_operator import EndomorphicOperator
22
from .linear_operator import LinearOperator
23
from .scaling_operator import ScalingOperator
Martin Reinecke's avatar
Martin Reinecke committed
24
25
26


class SandwichOperator(EndomorphicOperator):
Martin Reinecke's avatar
cleanup    
Martin Reinecke committed
27
    """Operator which is equivalent to the expression
28
29
    `bun.adjoint(cheese(bun))`.

Philipp Arras's avatar
Fixup    
Philipp Arras committed
30
31
    Note
    ----
32
33
    This operator should always be called using the `make` method.
    """
Martin Reinecke's avatar
Martin Reinecke committed
34

Martin Reinecke's avatar
Martin Reinecke committed
35
36
37
    def __init__(self, bun, cheese, op, _callingfrommake=False):
        if not _callingfrommake:
            raise NotImplementedError
Martin Reinecke's avatar
Martin Reinecke committed
38
        self._bun = bun
Martin Reinecke's avatar
Martin Reinecke committed
39
40
        self._cheese = cheese
        self._op = op
Martin Reinecke's avatar
Martin Reinecke committed
41
        self._domain = op.domain
Martin Reinecke's avatar
Martin Reinecke committed
42
        self._capability = op._capability
Martin Reinecke's avatar
Martin Reinecke committed
43
44
45
46
47
48
49
50
51
52
53
54

    @staticmethod
    def make(bun, cheese=None):
        """Build a SandwichOperator (or something simpler if possible)

        Parameters
        ----------
        bun: LinearOperator
            the bun part
        cheese: EndomorphicOperator
            the cheese part
        """
Martin Reinecke's avatar
Martin Reinecke committed
55
56
57
        if not isinstance(bun, LinearOperator):
            raise TypeError("bun must be a linear operator")
        if cheese is not None and not isinstance(cheese, LinearOperator):
Martin Reinecke's avatar
cleanup    
Martin Reinecke committed
58
            raise TypeError("cheese must be a linear operator or None")
59
        if cheese is None:
Martin Reinecke's avatar
Martin Reinecke committed
60
            cheese = ScalingOperator(1., bun.target)
Martin Reinecke's avatar
Martin Reinecke committed
61
            op = bun.adjoint(bun)
62
        else:
Martin Reinecke's avatar
Martin Reinecke committed
63
            op = bun.adjoint(cheese(bun))
Martin Reinecke's avatar
Martin Reinecke committed
64
65
66
67
68

        # if our sandwich is diagonal, we can return immediately
        if isinstance(op, (ScalingOperator, DiagonalOperator)):
            return op
        return SandwichOperator(bun, cheese, op, _callingfrommake=True)
Martin Reinecke's avatar
Martin Reinecke committed
69
70
71
72

    def apply(self, x, mode):
        return self._op.apply(x, mode)

73
    def draw_sample(self, from_inverse=False, dtype=np.float64):
Martin Reinecke's avatar
cleanup    
Martin Reinecke committed
74
        # Inverse samples from general sandwiches are not possible
75
        if from_inverse:
Martin Reinecke's avatar
Martin Reinecke committed
76
            if self._bun.capability & self._bun.INVERSE_TIMES:
77
78
79
                try:
                    s = self._cheese.draw_sample(from_inverse, dtype)
                    return self._bun.inverse_times(s)
Martin Reinecke's avatar
Martin Reinecke committed
80
                except NotImplementedError:
81
                    pass
82
83
            raise NotImplementedError(
                "cannot draw from inverse of this operator")
84
85

        # Samples from general sandwiches
86
87
        return self._bun.adjoint_times(
            self._cheese.draw_sample(from_inverse, dtype))
Martin Reinecke's avatar
Martin Reinecke committed
88
89
90
91
92
93
94
95

    def __repr__(self):
        from ..utilities import indent
        return "\n".join((
            "SandwichOperator:",
            indent("\n".join((
                "Cheese:", self._cheese.__repr__(),
                "Bun:", self._bun.__repr__())))))