gl_space.py 3.58 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/>.
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#
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# Copyright(C) 2013-2018 Max-Planck-Society
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#
# 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 __future__ import division
import numpy as np
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from .structured_domain import StructuredDomain
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class GLSpace(StructuredDomain):
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    """NIFTy subclass for Gauss-Legendre pixelizations of the two-sphere.

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    Its harmonic partner domain is the
    :class:`~nifty4.domains.lm_space.LMSpace`.
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    Parameters
    ----------
    nlat : int
        Number of latitudinal bins (or rings) that are used for this
        pixelization.
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    nlon : int, optional
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        Number of longitudinal bins that are used for this pixelization.
        Default value is 2*nlat + 1.
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    """

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    def __init__(self, nlat, nlon=None):
        super(GLSpace, self).__init__()
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        self._needed_for_hash += ["_nlat", "_nlon"]
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        self._nlat = int(nlat)
        if self._nlat < 1:
            raise ValueError("nlat must be a positive number.")
        if nlon is None:
            self._nlon = 2*self._nlat - 1
        else:
            self._nlon = int(nlon)
            if self._nlon < 1:
                raise ValueError("nlon must be a positive number.")
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        self._dvol = None
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    def __repr__(self):
        return ("GLSpace(nlat=%r, nlon=%r)" % (self.nlat, self.nlon))

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    @property
    def harmonic(self):
        return False
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    @property
    def shape(self):
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        return (np.int((self.nlat * self.nlon)),)
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    @property
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    def size(self):
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        return np.int((self.nlat * self.nlon))
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    def scalar_dvol(self):
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        return None

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    # MR FIXME: this is potentially wasteful, since the return array is
    #           blown up by a factor of self.nlon
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    def dvol(self):
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        from pyHealpix import GL_weights
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        if self._dvol is None:
            self._dvol = GL_weights(self.nlat, self.nlon)
        return np.repeat(self._dvol, self.nlon)
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    def total_volume(self):
        return 4*np.pi

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    @property
    def nlat(self):
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        """int : number of rings in this domain"""
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        return self._nlat

    @property
    def nlon(self):
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        """int : pixels per ring in this domain"""
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        return self._nlon

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    def get_default_codomain(self):
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        """Returns a :class:`LMSpace` object, which is capable of storing an
        accurate representation of data residing on `self` (if this data is
        band-limited).

        Returns
        -------
        LMSpace
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            The partner domain
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        """
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        from .. import LMSpace
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        return LMSpace(lmax=self._nlat-1, mmax=self._nlon//2)
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    def check_codomain(self, codomain):
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        """Raises `TypeError` if `codomain` is not a matching partner domain
        for `self`.

        Notes
        -----
        This function only checks whether `codomain` is of type
        :class:`LMSpace`.
        """
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        from .. import LMSpace
        if not isinstance(codomain, LMSpace):
            raise TypeError("codomain must be a LMSpace.")