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scattering_problem_engine.py
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Sun, Jun 30, 20:48

scattering_problem_engine.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/>.
#
from numpy import inf
import fenics as fen
from rrompy.utilities.base.types import paramVal
from rrompy.solver.fenics import fenZERO
from rrompy.utilities.base import verbosityManager as vbMng
from .helmholtz_problem_engine import HelmholtzProblemEngine
from rrompy.utilities.exception_manager import RROMPyWarning
from rrompy.solver.fenics import fenics2Sparse
__all__ = ['ScatteringProblemEngine']
class ScatteringProblemEngine(HelmholtzProblemEngine):
"""
Solver for scattering problems with parametric wavenumber.
- \nabla \cdot (a \nabla u) - omega^2 * n**2 * u = f in \Omega
u = u0 on \Gamma_D
\partial_nu = g1 on \Gamma_N
\partial_nu +- i omega u = g2 on \Gamma_R
Attributes:
verbosity: Verbosity level.
BCManager: Boundary condition manager.
V: Real FE space.
u: Generic trial functions for variational form evaluation.
v: Generic test functions for variational form evaluation.
As: Scipy sparse array representation (in CSC format) of As.
bs: Numpy array representation of bs.
cs: Numpy array representation of cs.
energyNormMatrix: Scipy sparse matrix representing inner product over
V.
energyNormDualMatrix: Scipy sparse matrix representing dual inner
product between Riesz representers V-V.
degree_threshold: Threshold for ufl expression interpolation degree.
signR: Sign in ABC.
omega: Value of omega.
diffusivity: Value of a.
forcingTerm: Value of f.
DirichletDatum: Value of u0.
NeumannDatum: Value of g1.
RobinDatumG: Value of g2.
DirichletBoundary: Function handle to \Gamma_D.
NeumannBoundary: Function handle to \Gamma_N.
RobinBoundary: Function handle to \Gamma_R.
ds: Boundary measure 2-tuple (resp. for Neumann and Robin boundaries).
dsToBeSet: Whether ds needs to be set.
"""
def __init__(self, mu0 : paramVal = [0.], degree_threshold : int = inf,
verbosity : int = 10, timestamp : bool = True):
self.silenceWarnings = True
super().__init__(mu0 = mu0, degree_threshold = degree_threshold,
verbosity = verbosity, timestamp = timestamp)
self._affinePoly = True
del self.silenceWarnings
self.nAs = 3
self.rescalingExp = [1.] + self.rescalingExp[1 :]
self.signR = - 1.
@property
def RobinDatumH(self):
"""Value of h."""
return self.signR * self.omega
@RobinDatumH.setter
def RobinDatumH(self, RobinDatumH):
if not hasattr(self, "silenceWarnings"):
RROMPyWarning(("Scattering problems do not allow changes of h. "
"Ignoring assignment."))
return
@property
def signR(self):
"""Value of signR."""
return self._signR
@signR.setter
def signR(self, signR):
self.resetAs()
self._signR = signR
def buildA(self):
"""Build terms of operator of linear system."""
if self.thAs[0] is None: self.thAs = self.getMonomialWeights(self.nAs)
if self.As[0] is None:
vbMng(self, "INIT", "Assembling operator term A0.", 20)
DirichletBC0 = fen.DirichletBC(self.V, fenZERO,
self.DirichletBoundary)
aRe, aIm = self.diffusivity
parsRe = self.iterReduceQuadratureDegree(zip([aRe],
["diffusivityReal"]))
parsIm = self.iterReduceQuadratureDegree(zip([aIm],
["diffusivityImag"]))
a0Re = aRe * fen.dot(fen.grad(self.u), fen.grad(self.v)) * fen.dx
a0Im = aIm * fen.dot(fen.grad(self.u), fen.grad(self.v)) * fen.dx
self.As[0] = (fenics2Sparse(a0Re, parsRe, DirichletBC0, 1)
+ 1.j * fenics2Sparse(a0Im, parsIm, DirichletBC0, 0))
vbMng(self, "DEL", "Done assembling operator term.", 20)
if self.As[1] is None:
self.autoSetDS()
vbMng(self, "INIT", "Assembling operator term A1.", 20)
DirichletBC0 = fen.DirichletBC(self.V, fenZERO,
self.DirichletBoundary)
a1 = fen.dot(self.u, self.v) * self.ds(1)
self.As[1] = (self.signR * 1.j
* fenics2Sparse(a1, {}, DirichletBC0, 0))
vbMng(self, "DEL", "Done assembling operator term.", 20)
if self.As[2] is None:
vbMng(self, "INIT", "Assembling operator term A2.", 20)
DirichletBC0 = fen.DirichletBC(self.V, fenZERO,
self.DirichletBoundary)
nRe, nIm = self.refractionIndex
n2Re, n2Im = nRe * nRe - nIm * nIm, 2 * nRe * nIm
parsRe = self.iterReduceQuadratureDegree(zip([n2Re],
["refractionIndexSquaredReal"]))
parsIm = self.iterReduceQuadratureDegree(zip([n2Im],
["refractionIndexSquaredImag"]))
a2Re = - n2Re * fen.dot(self.u, self.v) * fen.dx
a2Im = - n2Im * fen.dot(self.u, self.v) * fen.dx
self.As[2] = (fenics2Sparse(a2Re, parsRe, DirichletBC0, 0)
+ 1.j * fenics2Sparse(a2Im, parsIm, DirichletBC0, 0))
vbMng(self, "DEL", "Done assembling operator term.", 20)

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