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fft_sampler.py
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Tue, May 7, 16:27

fft_sampler.py
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# Copyright (C) 2018 by the RROMPy authors
#
# This file is part of RROMPy.
#
# RROMPy is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# RROMPy 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with RROMPy. If not, see <http://www.gnu.org/licenses/>.
#
import numpy as np
from .generic_sampler import GenericSampler
from rrompy.utilities.base.types import paramList
from rrompy.utilities.numerical import lowDiscrepancy, kroneckerer
from rrompy.parameter import checkParameterList
__all__ = ['FFTSampler']
class FFTSampler(GenericSampler):
"""Generator of FFT-type sample points on scaled roots of unity."""
def generatePoints(self, n:int, reorder : bool = True) -> paramList:
"""Array of sample points."""
n1d = int(np.ceil(n ** (1. / self.npar)))
nleft, nright = 1, n1d ** self.npar
xmat = np.empty((nright, self.npar), dtype = np.complex)
for d in range(self.npar):
nright //= n1d
a = self.lims(0, d) ** self.scalingExp[d]
b = self.lims(1, d) ** self.scalingExp[d]
c, r = (a + b) / 2., (a - b) / 2.
xd = c + r * np.exp(1.j * np.linspace(0, 2 * np.pi, n1d + 1)[:-1])
xd **= 1. / self.scalingExp[d]
if n1d > 1 and reorder:
fejerOrdering = [n1d - 1] + lowDiscrepancy(n1d - 1)
xd = xd[fejerOrdering]
xmat[:, d] = kroneckerer(xd, nleft, nright)
nleft *= n1d
x = checkParameterList(xmat, self.npar)[0]
return x

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