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rb_centered.py
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rb_centered.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 copy import deepcopy as copy
import numpy as np
from .generic_centered_approximant import GenericCenteredApproximant
from rrompy.reduction_methods.trained_model import TrainedModelRB as tModel
from rrompy.reduction_methods.trained_model import TrainedModelData
from rrompy.reduction_methods.base.rb_utils import projectAffineDecomposition
from rrompy.utilities.base.types import (Np1D, Np2D, Tuple, List, DictAny,
HFEng, paramVal, sampList)
from rrompy.utilities.base import purgeDict, verbosityDepth
from rrompy.utilities.exception_manager import RROMPyException, RROMPyWarning
__all__ = ['RBCentered']
class RBCentered(GenericCenteredApproximant):
"""
ROM single-point fast RB approximant computation for parametric problems
with polynomial dependence up to degree 2.
Args:
HFEngine: HF problem solver.
mu0(optional): Default parameter. Defaults to 0.
approxParameters(optional): Dictionary containing values for main
parameters of approximant. Recognized keys are:
- 'POD': whether to compute POD of snapshots; defaults to True;
- 'R': rank for Galerkin projection; defaults to E + 1;
- 'E': total number of derivatives current approximant relies upon;
defaults to 1.
Defaults to empty dict.
homogeneized(optional): Whether to homogeneize Dirichlet BCs. Defaults
to False.
verbosity(optional): Verbosity level. Defaults to 10.
Attributes:
HFEngine: HF problem solver.
mu0: Default parameter.
homogeneized: Whether to homogeneize Dirichlet BCs.
approxParameters: Dictionary containing values for main parameters of
approximant. Recognized keys are in parameterList.
parameterList: Recognized keys of approximant parameters:
- 'POD': whether to compute POD of snapshots;
- 'R': rank for Galerkin projection;
- 'E': total number of derivatives current approximant relies upon.
POD: Whether to compute QR factorization of derivatives.
R: Rank for Galerkin projection.
E: Number of solution derivatives over which current approximant is
based upon.
uHF: High fidelity solution with wavenumber lastSolvedHF as numpy
complex vector.
lastSolvedHF: Wavenumber corresponding to last computed high fidelity
solution.
uApp: Last evaluated approximant as numpy complex vector.
ARBs: List of sparse matrices (in CSC format) representing RB
coefficients of linear system matrix wrt mu.
bRBs: List of numpy vectors representing RB coefficients of linear
system RHS wrt mu.
"""
def __init__(self, HFEngine:HFEng, mu0 : paramVal = 0,
approxParameters : DictAny = {}, homogeneized : bool = False,
verbosity : int = 10, timestamp : bool = True):
self._preInit()
self._addParametersToList(["R"])
super().__init__(HFEngine = HFEngine, mu0 = mu0,
approxParameters = approxParameters,
homogeneized = homogeneized,
verbosity = verbosity, timestamp = timestamp)
if self.verbosity >= 10:
verbosityDepth("INIT", "Computing affine blocks of system.",
timestamp = self.timestamp)
if self.verbosity >= 10:
verbosityDepth("DEL", "Done computing affine blocks.",
timestamp = self.timestamp)
self._postInit()
@property
def approxParameters(self):
"""
Value of approximant parameters. Its assignment may change M, N and S.
"""
return self._approxParameters
@approxParameters.setter
def approxParameters(self, approxParams):
approxParameters = purgeDict(approxParams, self.parameterList,
dictname = self.name() + ".approxParameters",
baselevel = 1)
approxParametersCopy = purgeDict(approxParameters, ["R"],
True, True, baselevel = 1)
GenericCenteredApproximant.approxParameters.fset(self,
approxParametersCopy)
keyList = list(approxParameters.keys())
if "R" in keyList:
self.R = approxParameters["R"]
else:
self.R = self.E + 1
@property
def R(self):
"""Value of R. Its assignment may change S."""
return self._R
@R.setter
def R(self, R):
if R < 0: raise RROMPyException("R must be non-negative.")
self._R = R
self._approxParameters["R"] = self.R
if hasattr(self, "_E") and self.E + 1 < self.R:
RROMPyWarning("Prescribed E is too small. Updating E to R - 1.")
self.E = self.R - 1
def setupApprox(self):
"""Setup RB system."""
if self.checkComputedApprox():
return
if self.verbosity >= 5:
verbosityDepth("INIT", "Setting up {}.". format(self.name()),
timestamp = self.timestamp)
self.computeDerivatives()
if self.verbosity >= 7:
verbosityDepth("INIT", "Computing projection matrix.",
timestamp = self.timestamp)
if self.POD:
U, _, _ = np.linalg.svd(self.samplingEngine.RPOD[: self.E + 1,
: self.E + 1])
pMat = self.samplingEngine.samples(list(range(self.E + 1))).dot(
U[:, : self.R])
else:
pMat = self.samplingEngine.samples(list(range(self.R)))
if self.trainedModel is None:
self.trainedModel = tModel()
self.trainedModel.verbosity = self.verbosity
self.trainedModel.timestamp = self.timestamp
data = TrainedModelData(self.trainedModel.name(), self.mu0,
pMat, self.HFEngine.rescalingExp)
data.thetaAs = self.HFEngine.affineWeightsA(self.mu0)
data.thetabs = self.HFEngine.affineWeightsb(self.mu0,
self.homogeneized)
data.ARBs, data.bRBs = self.assembleReducedSystem(pMat)
self.trainedModel.data = data
else:
pMatOld = self.trainedModel.data.projMat
Sold = pMatOld.shape[1]
ARBs, bRBs = self.assembleReducedSystem(
pMat(list(range(Sold, pMat.shape[1]))), pMatOld)
self.trainedModel.data.ARBs = ARBs
self.trainedModel.data.bRBs = bRBs
self.trainedModel.data.projMat = copy(pMat)
if self.verbosity >= 7:
verbosityDepth("DEL", "Done computing projection matrix.",
timestamp = self.timestamp)
self.trainedModel.data.approxParameters = copy(self.approxParameters)
if self.verbosity >= 5:
verbosityDepth("DEL", "Done setting up approximant.",
timestamp = self.timestamp)
def assembleReducedSystem(self, pMat : sampList = None,
pMatOld : sampList = None)\
-> Tuple[List[Np2D], List[Np1D]]:
"""Build affine blocks of RB linear system through projections."""
if pMat is None:
self.setupApprox()
ARBs = self.trainedModel.data.ARBs
bRBs = self.trainedModel.data.bRBs
else:
if self.verbosity >= 10:
verbosityDepth("INIT", "Projecting affine terms of HF model.",
timestamp = self.timestamp)
As = self.HFEngine.affineLinearSystemA(self.mu0)
bs = self.HFEngine.affineLinearSystemb(self.mu0, self.homogeneized)
ARBsOld = None if pMatOld is None else self.trainedModel.data.ARBs
bRBsOld = None if pMatOld is None else self.trainedModel.data.bRBs
ARBs, bRBs = projectAffineDecomposition(As, bs, pMat, ARBsOld,
bRBsOld, pMatOld)
if self.verbosity >= 10:
verbosityDepth("DEL", "Done projecting affine terms.",
timestamp = self.timestamp)
return ARBs, bRBs

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