simple_linear_operators.py

# 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 ..domains.unstructured_domain import UnstructuredDomain
from ..field import Field
from ..multi_domain import MultiDomain
from ..multi_field import MultiField
from .endomorphic_operator import EndomorphicOperator
from .linear_operator import LinearOperator


class VdotOperator(LinearOperator):
    def __init__(self, field):
        self._field = field
        self._domain = field.domain
        self._target = DomainTuple.scalar_domain()
        self._capability = self.TIMES | self.ADJOINT_TIMES

    def apply(self, x, mode):
        self._check_mode(mode)
        if mode == self.TIMES:
            return Field.scalar(self._field.vdot(x))
        return self._field*x.local_data[()]


class ConjugationOperator(EndomorphicOperator):
    def __init__(self, domain):
        self._domain = DomainTuple.make(domain)
        self._capability = self._all_ops

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


class Realizer(EndomorphicOperator):
    def __init__(self, domain):
        self._domain = DomainTuple.make(domain)
        self._capability = self.TIMES | self.ADJOINT_TIMES

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


class _FieldAdapter(LinearOperator):
    """Operator for conversion between Fields and MultiFields.

    Parameters
    ----------
    tgt : Domain, tuple of Domain, DomainTuple, dict or MultiDomain:
        If this is a Domain, tuple of Domain or DomainTuple, this will be the
        operator's target, and its domain will be a MultiDomain consisting of
        its domain with the supplied `name`
        If this is a dict or MultiDomain, everything except for `name` will
        be stripped out of it, and the result will be the operator's target.
        Its domain will then be the DomainTuple corresponding to the single
        entry in the operator's domain.

    name : String
        The relevant key of the MultiDomain.
    """

    def __init__(self, tgt, name):
        from ..sugar import makeDomain
        tmp = makeDomain(tgt)
        if isinstance(tmp, DomainTuple):
            self._target = tmp
            self._domain = MultiDomain.make({name: tmp})
        else:
            self._domain = tmp[name]
            self._target = MultiDomain.make({name: tmp[name]})
        self._capability = self.TIMES | self.ADJOINT_TIMES

    def apply(self, x, mode):
        self._check_input(x, mode)
        if isinstance(x, MultiField):
            return x.values()[0]
        else:
            return MultiField(self._tgt(mode), (x,))

    def __repr__(self):
        key = self.domain.keys()[0]
        return 'FieldAdapter: {}'.format(key)


def ducktape(left, right, name):
    from ..sugar import makeDomain
    from .operator import Operator
    if left is None:  # need to infer left from right
        if isinstance(right, Operator):
            right = right.target
        elif right is not None:
            right = makeDomain(right)
        if isinstance(right, MultiDomain):
            left = right[name]
        else:
            left = MultiDomain.make({name: right})
    else:
        if isinstance(left, Operator):
            left = left.domain
        else:
            left = makeDomain(left)
    return _FieldAdapter(left, name)


class GeometryRemover(LinearOperator):
    """Operator which transforms between a structured and an unstructured
    domain.

    Parameters
    ----------
    domain: Domain, tuple of Domain, or DomainTuple:
        the full input domain of the operator.

    Notes
    -----
    The operator will convert every sub-domain of its input domain to an
    UnstructuredDomain with the same shape. No weighting by volume factors
    is carried out.
    """

    def __init__(self, domain):
        self._domain = DomainTuple.make(domain)
        target_list = [UnstructuredDomain(dom.shape) for dom in self._domain]
        self._target = DomainTuple.make(target_list)
        self._capability = self.TIMES | self.ADJOINT_TIMES

    def apply(self, x, mode):
        self._check_input(x, mode)
        return x.cast_domain(self._tgt(mode))


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)
        self._capability = self.TIMES | self.ADJOINT_TIMES

    @staticmethod
    def _nullfield(dom):
        if isinstance(dom, DomainTuple):
            return Field(dom, 0)
        else:
            return MultiField.full(dom, 0)

    def apply(self, x, mode):
        self._check_input(x, mode)
        return self._nullfield(self._tgt(mode))