Source code for nifty.operators.fft_operator.transformations.lmgltransformation

# NIFTy
# Copyright (C) 2017  Theo Steininger
#
# Author: Theo Steininger
#
# 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/>.

import numpy as np
from nifty.config import dependency_injector as gdi
from nifty import GLSpace, LMSpace

from slicing_transformation import SlicingTransformation
import lm_transformation_helper

pyHealpix = gdi.get('pyHealpix')


[docs]class LMGLTransformation(SlicingTransformation): # ---Overwritten properties and methods--- def __init__(self, domain, codomain=None, module=None): if module is None: module = 'pyHealpix' if module != 'pyHealpix': raise ValueError("Unsupported SHT module.") if 'pyHealpix' not in gdi: raise ImportError( "The module pyHealpix is needed but not available.") super(LMGLTransformation, self).__init__(domain, codomain, module) # ---Mandatory properties and methods--- @property def unitary(self): return False
[docs] @classmethod def get_codomain(cls, domain): """ Generates a compatible codomain to which transformations are reasonable, i.e.\ a pixelization of the two-sphere. Parameters ---------- domain : LMSpace Space for which a codomain is to be generated Returns ------- codomain : HPSpace A compatible codomain. References ---------- .. [#] M. Reinecke and D. Sverre Seljebotn, 2013, "Libsharp - spherical harmonic transforms revisited"; `arXiv:1303.4945 <http://www.arxiv.org/abs/1303.4945>`_ """ if not isinstance(domain, LMSpace): raise TypeError("domain needs to be a LMSpace") nlat = domain.lmax + 1 nlon = domain.lmax*2 + 1 result = GLSpace(nlat=nlat, nlon=nlon) return result
@classmethod def check_codomain(cls, domain, codomain): if not isinstance(domain, LMSpace): raise TypeError("domain is not a LMSpace") if not isinstance(codomain, GLSpace): raise TypeError("codomain must be a GLSpace.") nlat = codomain.nlat nlon = codomain.nlon lmax = domain.lmax mmax = domain.mmax if lmax != mmax: cls.logger.warn("Unrecommended: codomain has lmax != mmax.") if nlat != lmax + 1: cls.logger.warn("Unrecommended: codomain has nlat != lmax + 1.") if nlon != 2*lmax + 1: cls.logger.warn("Unrecommended: domain has nlon != 2*lmax + 1.") super(LMGLTransformation, cls).check_codomain(domain, codomain) def _transformation_of_slice(self, inp, **kwargs): if inp.dtype not in (np.float, np.complex): self.logger.warn("The input array has dtype: %s. The FFT will " "be performed at double precision." % str(inp.dtype)) nlat = self.codomain.nlat nlon = self.codomain.nlon lmax = self.domain.lmax mmax = self.domain.mmax sjob = pyHealpix.sharpjob_d() sjob.set_Gauss_geometry(nlat, nlon) sjob.set_triangular_alm_info(lmax, mmax) if issubclass(inp.dtype.type, np.complexfloating): [resultReal, resultImag] = [lm_transformation_helper.buildLm(x, lmax=lmax) for x in (inp.real, inp.imag)] [resultReal, resultImag] = [sjob.alm2map(x) for x in [resultReal, resultImag]] result = self._combine_complex_result(resultReal, resultImag) else: result = lm_transformation_helper.buildLm(inp, lmax=lmax) result = sjob.alm2map(result) return result