sugar.py 2.39 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
# 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/>.
18 19 20 21 22 23 24 25 26

from nifty import PowerSpace,\
                  Field,\
                  DiagonalOperator,\
                  FFTOperator

__all__ = ['create_power_operator']


27 28
def create_power_operator(domain, power_spectrum, dtype=None,
                          distribution_strategy='not'):
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
	"""Creates a diagonal operator with a certain power spectrum.
	Constructs a diagonal operator that lives over the specified domain, or
	its harmonic domain in case it is not harmonic.
	Parameters
	----------
	domain : DomainObject
		Domain over which the power operator shall live. If this is not a
		harmonic domain, it will return an operator for its harmonic domain
		instead.
	power_spectrum : {array-like, method}
		An array-like object, or a method that implements the square root
		of a power spectrum as a function of k.
	dtype : type, *optional*
		dtype that the field holding the power spectrum shall use
		{default : None}
			if dtype == None: passes this on to constructor of Field
	distribution_strategy : string, *optional*
		Distributed strategy to be used by the underlying d2o objects.
		{default : 'not'}
	Returns
	-------
	DiagonalOperator : An operator that lives that implements the given power
		spectrum.
	"""
53 54 55 56
    if not domain.harmonic:
        fft = FFTOperator(domain)
        domain = fft.target[0]

57 58
    power_domain = PowerSpace(domain,
                              distribution_strategy=distribution_strategy)
59 60

    fp = Field(power_domain,
61
               val=power_spectrum, dtype=dtype,
62
               distribution_strategy=distribution_strategy)
63
    fp **= 2
64

65
    f = fp.power_synthesize(mean=1, std=0, real_signal=False)
66

67
    power_operator = DiagonalOperator(domain, diagonal=f, bare=True)
68

69
    return power_operator