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laplace_disk_gaussian.py
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Tue, Nov 19, 01:43

laplace_disk_gaussian.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
import fenics as fen
from rrompy.utilities.base.types import Np1D, Tuple, FenExpr
from .laplace_base_problem_engine import LaplaceBaseProblemEngine
from rrompy.utilities.base.fenics import fenZERO, fenONE
from rrompy.utilities.base import verbosityDepth
__all__ = ['LaplaceDiskGaussian']
class LaplaceDiskGaussian(LaplaceBaseProblemEngine):
"""
Solver for disk Laplace problems with parametric forcing term center.
- \Delta u = C exp(-.5 * ||\cdot - (mu, 0)||^2) in \Omega = B(0, 5)
u = 0 on \partial\Omega.
"""
nbs = 20
def __init__(self, n:int, degree_threshold : int = np.inf,
verbosity : int = 10, timestamp : bool = True):
super().__init__(degree_threshold = degree_threshold,
verbosity = verbosity, timestamp = timestamp)
self.computebsFactors()
self.forcingTermMu = np.nan
import mshr
mesh = mshr.generate_mesh(mshr.Circle(fen.Point(0., 0.), 5.), n)
self.V = fen.FunctionSpace(mesh, "P", 3)
def getForcingTerm(self, mu:complex) -> Tuple[FenExpr, FenExpr]:
"""Compute forcing term."""
if not np.isclose(mu, self.forcingTermMu):
if self.verbosity >= 25:
verbosityDepth("INIT", ("Assembling base expression for "
"forcing term."),
timestamp = self.timestamp)
x, y = fen.SpatialCoordinate(self.V.mesh())[:]
C = np.exp(-.5 * mu ** 2.)
CR, CI = np.real(C), np.imag(C)
f0 = (2 * np.pi) ** -.5 * fen.exp(-.5 * (x ** 2. + y ** 2.))
muR, muI = np.real(mu), np.imag(mu)
f1R = fen.exp(muR * x) * fen.cos(muI * x)
f1I = fen.exp(muR * x) * fen.sin(muI * x)
self.forcingTerm = [f0 * (CR * f1R - CI * f1I),
f0 * (CR * f1I + CI * f1R)]
self.forcingTermMu = mu
if self.verbosity >= 25:
verbosityDepth("DEL", "Done assembling base expression.",
timestamp = self.timestamp)
return self.forcingTerm
def computebsFactors(self):
self.bsFactors = np.zeros((self.nbs, self.nbs), dtype = float)
self.bsFactors[0, 0] = 1.
self.bsFactors[1, 1] = 1.
for j in range(2, self.nbs):
l = (j + 1) % 2 + 1
J = np.arange(l, j + 1, 2)
self.bsFactors[j, J] = self.bsFactors[j - 1, J - 1]
if l == 2:
l = 0
J = np.arange(l, j, 2)
self.bsFactors[j, J] += np.multiply(- 1 - J,
self.bsFactors[j - 1, J + 1])
self.bsFactors[j, l : j + 2 : 2] /= j
def getExtraFactorB(self, mu:complex, der:int) -> Tuple[FenExpr, FenExpr]:
"""Compute extra expression in RHS."""
if self.verbosity >= 25:
verbosityDepth("INIT", ("Assembling auxiliary expression for "
"forcing term derivative."),
timestamp = self.timestamp)
muR, muI = np.real(mu), np.imag(mu)
x = fen.SpatialCoordinate(self.V.mesh())[0]
l = der % 2
if l == 0:
powR, powI = fenONE, fenZERO
else:
powR, powI = x - muR, fen.Constant(muI)
exprR, exprI = [self.bsFactors[der, l] * k for k in [powR, powI]]
for j in range(l + 2, der + 1, 2):
for _ in range(2):
powR, powI = (powR * (x - muR) - powI * muI,
powR * muI + powI * (x - muR))
exprR += self.bsFactors[der, j] * powR
exprI += self.bsFactors[der, j] * powI
if self.verbosity >= 25:
verbosityDepth("DEL", "Done assembling auxiliary expression.",
timestamp = self.timestamp)
return[exprR, exprI]
def b(self, mu:complex, der : int = 0,
homogeneized : bool = False) -> Np1D:
"""Assemble (derivative of) RHS of linear system."""
bnull = self.checkbInBounds(der, homogeneized)
if bnull is not None: return bnull
if homogeneized and not np.isclose(self.mu0BC, mu):
self.u0BC = self.liftDirichletData(mu)
if not np.isclose(self.bsmu, mu):
self.bsmu = mu
self.resetbs()
if self.bs[homogeneized][der] is None:
if self.verbosity >= 20:
verbosityDepth("INIT", "Assembling forcing term b{}.".format(
der),
timestamp = self.timestamp)
if der < self.nbs:
fRe, fIm = self.getForcingTerm(mu)
cRe, cIm = self.getExtraFactorB(mu, der)
cfRe = cRe * fRe - cIm * fIm
cfIm = cRe * fIm + cIm * fRe
else:
cfRe, cfIm = fenZERO, fenZERO
parsRe = self.iterReduceQuadratureDegree(zip([cfRe],
["forcingTermDer{}Real".format(der)]))
parsIm = self.iterReduceQuadratureDegree(zip([cfIm],
["forcingTermDer{}Imag".format(der)]))
L0Re = fen.dot(cfRe, self.v) * fen.dx
L0Im = fen.dot(cfIm, self.v) * fen.dx
b0Re = fen.assemble(L0Re, form_compiler_parameters = parsRe)
b0Im = fen.assemble(L0Im, form_compiler_parameters = parsIm)
if homogeneized:
Ader = self.A(mu, der)
b0Re[:] -= np.real(Ader.dot(self.u0BC))
b0Im[:] -= np.imag(Ader.dot(self.u0BC))
DirichletBC0 = fen.DirichletBC(self.V, fenZERO,
self.DirichletBoundary)
DirichletBC0.apply(b0Re)
DirichletBC0.apply(b0Im)
self.bs[homogeneized][der] = np.array(b0Re[:]
+ 1.j * b0Im[:], dtype = np.complex)
if self.verbosity >= 20:
verbosityDepth("DEL", "Done assembling forcing term.",
timestamp = self.timestamp)
return self.bs[homogeneized][der]

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