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fft_sampler.py
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Tue, May 14, 22:42

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 Np1D, List, Tuple, paramList
from rrompy.utilities.base 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:List[int],
reorder : bool = True) -> Tuple[paramList, Np1D]:
"""Array of sample points and array of weights."""
if not hasattr(n, "__len__"): n = [n]
super().generatePoints(n)
nleft, nright = 1, np.prod(n)
xmat = np.empty((nright, self.npar), dtype = np.complex)
wdMult = 1.
for d in range(self.npar):
nright //= n[d]
a, b = self.lims[0](d), self.lims[1](d)
if self.scaling is not None:
a, b = self.scaling[d](a), self.scaling[d](b)
c, r = (a + b) / 2., np.abs(a - b) / 2.
xd = c + r * np.exp(1.j * np.linspace(0, 2 * np.pi, n[d] + 1)[:-1])
wdMult *= r / n[d]
if reorder:
fejerOrdering = lowDiscrepancy(n[d])
xd = xd[fejerOrdering]
if self.scalingInv is not None:
xd = self.scalingInv[d](xd)
xmat[:, d] = kroneckerer(xd, nleft, nright)
nleft *= n[d]
x, _ = checkParameterList(xmat, self.npar)
return x, wdMult * np.ones(len(x))

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