selection_operator.py 1.9 KB
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# 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.

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from .linear_operator import LinearOperator
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from ..multi.multi_domain import MultiDomain
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class SelectionOperator(LinearOperator):
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    """Extracts from a MultiField a copy of the Field
    living on the subdomain selected by `key`.

    Parameters
    ----------
    domain : :class:`MultiDomain`
        Domain of the MultiFields to be acted on
    key : :class:`str`
        String identifier of the wanted subdomain
    """
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    def __init__(self, domain, key):
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        self._domain = MultiDomain.make(domain)
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        self._key = key

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

    @property
    def target(self):
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        return self._domain[self._key]
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    @property
    def capability(self):
        return self.TIMES | self.ADJOINT_TIMES

    def apply(self, x, mode):
        self._check_input(x, mode)
        if mode == self.TIMES:
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            return x[self._key]
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        else:
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            from ..multi.multi_field import MultiField
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            rval = [None]*len(self._domain)
            rval[self._domain._dict[self._key]] = x
            return MultiField(self._domain, tuple(rval))