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reduced_basis.py
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reduced_basis.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_standard_approximant import GenericStandardApproximant
from rrompy.reduction_methods.trained_model import \
TrainedModelReducedBasis as tModel
from rrompy.reduction_methods.trained_model import TrainedModelData
from rrompy.reduction_methods.base.reduced_basis_utils import \
projectAffineDecomposition
from rrompy.utilities.base.types import (Np1D, Np2D, List, ListAny, Tuple,
DictAny, HFEng, paramVal, sampList)
from rrompy.utilities.base import verbosityManager as vbMng
from rrompy.utilities.exception_manager import (RROMPyWarning, RROMPyException,
RROMPyAssert)
__all__ = ['ReducedBasis']
class ReducedBasis(GenericStandardApproximant):
"""
ROM RB approximant computation for parametric problems.
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;
- 'S': total number of samples current approximant relies upon;
- 'sampler': sample point generator;
- 'R': rank for Galerkin projection; defaults to prod(S);
- 'PODTolerance': tolerance for snapshots POD; 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.
mus: Array of snapshot parameters.
homogeneized: Whether to homogeneize Dirichlet BCs.
approxRadius: Dummy radius of approximant (i.e. distance from mu0 to
farthest sample point).
approxParameters: Dictionary containing values for main parameters of
approximant. Recognized keys are in parameterList.
parameterListSoft: Recognized keys of soft approximant parameters:
- 'POD': whether to compute POD of snapshots.
- 'R': rank for Galerkin projection;
- 'PODTolerance': tolerance for snapshots POD.
parameterListCritical: Recognized keys of critical approximant
parameters:
- 'S': total number of samples current approximant relies upon;
- 'sampler': sample point generator;
POD: Whether to compute POD of snapshots.
S: Number of solution snapshots over which current approximant is
based upon.
sampler: Sample point generator.
R: Rank for Galerkin projection.
muBounds: list of bounds for parameter values.
samplingEngine: Sampling engine.
uHF: High fidelity solution(s) with parameter(s) lastSolvedHF as
sampleList.
lastSolvedHF: Parameter(s) corresponding to last computed high fidelity
solution(s) as parameterList.
uApproxReduced: Reduced approximate solution(s) with parameter(s)
lastSolvedApprox as sampleList.
lastSolvedApproxReduced: Parameter(s) corresponding to last computed
reduced approximate solution(s) as parameterList.
uApprox: Approximate solution(s) with parameter(s) lastSolvedApprox as
sampleList.
lastSolvedApprox: Parameter(s) corresponding to last computed
approximate solution(s) as parameterList.
As: List of sparse matrices (in CSC format) representing coefficients
of linear system matrix.
bs: List of numpy vectors representing coefficients of linear system
RHS.
ARBs: List of sparse matrices (in CSC format) representing coefficients
of compressed linear system matrix.
bRBs: List of numpy vectors representing coefficients of compressed
linear system RHS.
"""
def __init__(self, HFEngine:HFEng, mu0 : paramVal = None,
approxParameters : DictAny = {}, homogeneized : bool = False,
verbosity : int = 10, timestamp : bool = True):
self._preInit()
self._addParametersToList(["R", "PODTolerance"], [1, -1])
super().__init__(HFEngine = HFEngine, mu0 = mu0,
approxParameters = approxParameters,
homogeneized = homogeneized,
verbosity = verbosity, timestamp = timestamp)
vbMng(self, "INIT", "Computing affine blocks of system.", 10)
vbMng(self, "DEL", "Done computing affine blocks.", 10)
self._postInit()
@property
def S(self):
"""Value of S."""
return self._S
@S.setter
def S(self, S):
GenericStandardApproximant.S.fset(self, S)
if not hasattr(self, "_R"): self._R = np.prod(self.S)
@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, "_S") and np.prod(self.S) < self.R:
RROMPyWarning("Prescribed S is too small. Decreasing R.")
self.R = np.prod(self.S)
@property
def PODTolerance(self):
"""Value of PODTolerance."""
return self._PODTolerance
@PODTolerance.setter
def PODTolerance(self, PODTolerance):
self._PODTolerance = PODTolerance
self._approxParameters["PODTolerance"] = self.PODTolerance
def setupApprox(self):
"""Compute RB projection matrix."""
if self.checkComputedApprox():
return
RROMPyAssert(self._mode, message = "Cannot setup approximant.")
vbMng(self, "INIT", "Setting up {}.". format(self.name()), 5)
self.computeScaleFactor()
self.computeSnapshots()
vbMng(self, "INIT", "Computing projection matrix.", 7)
if self.POD:
U, s, _ = np.linalg.svd(self.samplingEngine.RPOD)
s = s ** 2.
else:
Gramian = self.HFEngine.innerProduct(self.samplingEngine.samples,
self.samplingEngine.samples)
U, s, _ = np.linalg.svd(Gramian)
nsamples = self.samplingEngine.nsamples
snorm = np.cumsum(s[::-1]) / np.sum(s)
nPODTrunc = min(nsamples - np.argmax(snorm > self.PODTolerance),
self.R)
pMat = self.samplingEngine.samples.dot(U[:, : nPODTrunc])
vbMng(self, "MAIN",
("Assembling {}x{} projection matrix from {} "
"samples.").format(*(pMat.shape), nsamples), 5)
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.scaleFactor,
self.HFEngine.rescalingExp)
data.mus = copy(self.mus)
self.trainedModel.data = data
else:
self.trainedModel = self.trainedModel
self.trainedModel.data.projMat = copy(pMat)
vbMng(self, "INIT", "Computing affine blocks of system.", 10)
self.As = self.HFEngine.affineLinearSystemA(self.mu0, self.scaleFactor)
self.bs = self.HFEngine.affineLinearSystemb(self.mu0, self.scaleFactor,
self.homogeneized)
vbMng(self, "DEL", "Done computing affine blocks.", 10)
ARBs, bRBs = self.assembleReducedSystem(pMat)
self.trainedModel.data.ARBs = ARBs
self.trainedModel.data.bRBs = bRBs
vbMng(self, "DEL", "Done computing projection matrix.", 7)
self.trainedModel.data.approxParameters = copy(self.approxParameters)
vbMng(self, "DEL", "Done setting up approximant.", 5)
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:
vbMng(self, "INIT", "Projecting affine terms of HF model.", 10)
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(self.As, self.bs, pMat,
ARBsOld, bRBsOld, pMatOld)
vbMng(self, "DEL", "Done projecting affine terms.", 10)
return ARBs, bRBs

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