null_operator.py 2.05 KB
Newer Older
Martin Reinecke's avatar
Martin Reinecke committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
# 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/>.
#
# Copyright(C) 2013-2018 Max-Planck-Society
#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.

from __future__ import absolute_import, division, print_function
from ..compat import *
from ..domain_tuple import DomainTuple
from ..field import Field
from ..multi.multi_field import MultiField
from ..operators.linear_operator import LinearOperator


class NullOperator(LinearOperator):
    """Operator corresponding to a matrix of all zeros.

    Parameters
    ----------
    domain : DomainTuple or MultiDomain
        input domain
    target : DomainTuple or MultiDomain
        output domain
    """
    def __init__(self, domain, target):
        from ..sugar import makeDomain
        self._domain = makeDomain(domain)
        self._target = makeDomain(target)

    @staticmethod
    def _nullfield(dom):
        if isinstance (dom, DomainTuple):
Martin Reinecke's avatar
fix  
Martin Reinecke committed
45
            return Field.full(dom, 0)
Martin Reinecke's avatar
Martin Reinecke committed
46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
        else:
            return MultiField(dom, (None,)*len(dom))

    def apply(self, x, mode):
        self._check_input(x, mode)

        if mode == self.TIMES:
            return self._nullfield(self._target)
        return self._nullfield(self._domain)

    @property
    def domain(self):
        return self._domain

    @property
    def target(self):
        return self._target

    @property
    def capability(self):
        return self.TIMES | self.ADJOINT_TIMES