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rational_interpolant_greedy.py
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rational_interpolant_greedy.py

# 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 rrompy.hfengines.base.linear_affine_engine import checkIfAffine
from .generic_greedy_approximant import GenericGreedyApproximant
from rrompy.utilities.poly_fitting.polynomial import (polybases, polyfitname,
PolynomialInterpolator as PI,
polyvander)
from rrompy.utilities.numerical import dot
from rrompy.utilities.numerical.degree import totalDegreeN
from rrompy.utilities.expression import expressionEvaluator
from rrompy.reduction_methods.standard import RationalInterpolant
from rrompy.utilities.base.types import Np1D, Tuple, paramVal, List
from rrompy.utilities.base.verbosity_depth import (verbosityManager as vbMng,
getVerbosityDepth, setVerbosityDepth)
from rrompy.utilities.poly_fitting import customFit
from rrompy.utilities.exception_manager import (RROMPyWarning, RROMPyException,
RROMPyAssert, RROMPy_FRAGILE)
from rrompy.sampling import sampleList, emptySampleList
__all__ = ['RationalInterpolantGreedy']
class RationalInterpolantGreedy(GenericGreedyApproximant, RationalInterpolant):
"""
ROM greedy rational interpolant 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': kind of snapshots orthogonalization; allowed values
include 0, 1/2, and 1; defaults to 1, i.e. POD;
- 'scaleFactorDer': scaling factors for derivative computation;
defaults to 'AUTO';
- 'S': number of starting training points;
- 'sampler': sample point generator;
- 'greedyTol': uniform error tolerance for greedy algorithm;
defaults to 1e-2;
- 'collinearityTol': collinearity tolerance for greedy algorithm;
defaults to 0.;
- 'maxIter': maximum number of greedy steps; defaults to 1e2;
- 'nTestPoints': number of test points; defaults to 5e2;
- 'trainSetGenerator': training sample points generator; defaults
to sampler;
- 'polybasis': type of basis for interpolation; defaults to
'MONOMIAL';
- 'errorEstimatorKind': kind of error estimator; available values
include 'AFFINE', 'DISCREPANCY', 'LOOK_AHEAD',
'LOOK_AHEAD_RES', 'LOOK_AHEAD_OUTPUT', and 'NONE'; defaults to
'NONE';
- 'functionalSolve': strategy for minimization of denominator
functional; allowed values include 'NORM', 'DOMINANT', 'NODAL',
'BARYCENTRIC_NORM', and 'BARYCENTRIC[_AVERAGE]' (check pdf in
main folder for meaning); defaults to 'NORM';
- 'interpRcond': tolerance for interpolation; defaults to None;
- 'robustTol': tolerance for robust rational denominator
management; defaults to 0.
Defaults to empty dict.
approx_state(optional): Whether to approximate state. Defaults and must
be True.
verbosity(optional): Verbosity level. Defaults to 10.
Attributes:
HFEngine: HF problem solver.
mu0: Default parameter.
mus: Array of snapshot parameters.
approxParameters: Dictionary containing values for main parameters of
approximant. Recognized keys are in parameterList.
parameterListSoft: Recognized keys of soft approximant parameters:
- 'POD': kind of snapshots orthogonalization;
- 'scaleFactorDer': scaling factors for derivative computation;
- 'greedyTol': uniform error tolerance for greedy algorithm;
- 'collinearityTol': collinearity tolerance for greedy algorithm;
- 'maxIter': maximum number of greedy steps;
- 'nTestPoints': number of test points;
- 'trainSetGenerator': training sample points generator;
- 'errorEstimatorKind': kind of error estimator;
- 'functionalSolve': strategy for minimization of denominator
functional;
- 'interpRcond': tolerance for interpolation;
- 'robustTol': tolerance for robust rational denominator
management.
parameterListCritical: Recognized keys of critical approximant
parameters:
- 'S': total number of samples current approximant relies upon;
- 'sampler': sample point generator.
approx_state: Whether to approximate state.
verbosity: Verbosity level.
POD: Kind of snapshots orthogonalization.
scaleFactorDer: Scaling factors for derivative computation.
S: number of test points.
sampler: Sample point generator.
greedyTol: uniform error tolerance for greedy algorithm.
collinearityTol: Collinearity tolerance for greedy algorithm.
maxIter: maximum number of greedy steps.
nTestPoints: number of starting training points.
trainSetGenerator: training sample points generator.
robustTol: tolerance for robust rational denominator management.
errorEstimatorKind: kind of error estimator.
functionalSolve: Strategy for minimization of denominator functional.
interpRcond: tolerance for interpolation.
robustTol: tolerance for robust rational denominator management.
muBounds: list of bounds for parameter values.
samplingEngine: Sampling engine.
estimatorNormEngine: Engine for estimator norm computation.
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.
"""
_allowedEstimatorKinds = ["AFFINE", "DISCREPANCY", "LOOK_AHEAD",
"LOOK_AHEAD_RES", "LOOK_AHEAD_OUTPUT", "NONE"]
def __init__(self, *args, **kwargs):
self._preInit()
self._addParametersToList(["errorEstimatorKind"], ["DISCREPANCY"],
toBeExcluded = ["M", "N", "polydegreetype",
"radialDirectionalWeights"])
super().__init__(*args, **kwargs)
if not self.approx_state and self.errorEstimatorKind not in [
"LOOK_AHEAD", "LOOK_AHEAD_OUTPUT", "NONE"]:
raise RROMPyException(("Must compute greedy approximation of "
"state, unless error estimator allows "
"otherwise."))
self._postInit()
@property
def approx_state(self):
"""Value of approx_state."""
return self._approx_state
@approx_state.setter
def approx_state(self, approx_state):
RationalInterpolant.approx_state.fset(self, approx_state)
if (not self.approx_state and hasattr(self, "_errorEstimatorKind")
and self.errorEstimatorKind not in [
"LOOK_AHEAD", "LOOK_AHEAD_OUTPUT", "NONE"]):
raise RROMPyException(("Must compute greedy approximation of "
"state, unless error estimator allows "
"otherwise."))
@property
def E(self):
"""Value of E."""
self._E = self.sampleBatchIdx - 1
return self._E
@E.setter
def E(self, E):
RROMPyWarning(("E is used just to simplify inheritance, and its value "
"cannot be changed from that of sampleBatchIdx - 1."))
def _setMAuto(self):
self.M = self.E
def _setNAuto(self):
self.N = self.E
@property
def polydegreetype(self):
"""Value of polydegreetype."""
return "TOTAL"
@polydegreetype.setter
def polydegreetype(self, polydegreetype):
RROMPyWarning(("polydegreetype is used just to simplify inheritance, "
"and its value cannot be changed from 'TOTAL'."))
@property
def polybasis(self):
"""Value of polybasis."""
return self._polybasis
@polybasis.setter
def polybasis(self, polybasis):
try:
polybasis = polybasis.upper().strip().replace(" ","")
if polybasis not in polybases:
raise RROMPyException("Sample type not recognized.")
self._polybasis = polybasis
except:
RROMPyWarning(("Prescribed polybasis not recognized. Overriding "
"to 'MONOMIAL'."))
self._polybasis = "MONOMIAL"
self._approxParameters["polybasis"] = self.polybasis
@property
def errorEstimatorKind(self):
"""Value of errorEstimatorKind."""
return self._errorEstimatorKind
@errorEstimatorKind.setter
def errorEstimatorKind(self, errorEstimatorKind):
errorEstimatorKind = errorEstimatorKind.upper()
if errorEstimatorKind not in self._allowedEstimatorKinds:
RROMPyWarning(("Error estimator kind not recognized. Overriding "
"to 'NONE'."))
errorEstimatorKind = "NONE"
self._errorEstimatorKind = errorEstimatorKind
self._approxParameters["errorEstimatorKind"] = self.errorEstimatorKind
if (self.errorEstimatorKind not in [
"LOOK_AHEAD", "LOOK_AHEAD_OUTPUT", "NONE"]
and hasattr(self, "_approx_state") and not self.approx_state):
raise RROMPyException(("Must compute greedy approximation of "
"state, unless error estimator allows "
"otherwise."))
def _polyvanderAuxiliary(self, mus, deg, *args):
return polyvander(mus, deg, *args)
def getErrorEstimatorDiscrepancy(self, mus:Np1D) -> Np1D:
"""Discrepancy-based residual estimator."""
checkIfAffine(self.HFEngine, "apply discrepancy-based error estimator")
mus = self.checkParameterList(mus)
muCTest = self.trainedModel.centerNormalize(mus)
tMverb, self.trainedModel.verbosity = self.trainedModel.verbosity, 0
QTest = self.trainedModel.getQVal(mus)
QTzero = np.where(QTest == 0.)[0]
if len(QTzero) > 0:
RROMPyWarning(("Adjusting estimator to avoid division by "
"numerically zero denominator."))
QTest[QTzero] = np.finfo(np.complex).eps / (1. + self.N)
self.HFEngine.buildA()
self.HFEngine.buildb()
nAs, nbs = self.HFEngine.nAs, self.HFEngine.nbs
muTrainEff = self.mapParameterList(self.mus)
muTestEff = self.mapParameterList(mus)
PTrain = self.trainedModel.getPVal(self.mus).data.T
QTrain = self.trainedModel.getQVal(self.mus)
QTzero = np.where(QTrain == 0.)[0]
if len(QTzero) > 0:
RROMPyWarning(("Adjusting estimator to avoid division by "
"numerically zero denominator."))
QTrain[QTzero] = np.finfo(np.complex).eps / (1. + self.N)
PTest = self.trainedModel.getPVal(mus).data
self.trainedModel.verbosity = tMverb
radiusAbTrain = np.empty((self.S, nAs * self.S + nbs),
dtype = np.complex)
radiusA = np.empty((self.S, nAs, len(mus)), dtype = np.complex)
radiusb = np.empty((nbs, len(mus)), dtype = np.complex)
for j, thA in enumerate(self.HFEngine.thAs):
idxs = j * self.S + np.arange(self.S)
radiusAbTrain[:, idxs] = expressionEvaluator(thA[0], muTrainEff,
(self.S, 1)) * PTrain
radiusA[:, j] = PTest * expressionEvaluator(thA[0], muTestEff,
(len(mus),))
for j, thb in enumerate(self.HFEngine.thbs):
idx = nAs * self.S + j
radiusAbTrain[:, idx] = QTrain * expressionEvaluator(thb[0],
muTrainEff, (self.S,))
radiusb[j] = QTest * expressionEvaluator(thb[0], muTestEff,
(len(mus),))
QRHSNorm2 = self._affineResidualMatricesContraction(radiusb)
vanTrain = self._polyvanderAuxiliary(self._musUniqueCN, self.E,
self.polybasis0, self._derIdxs,
self._reorder)
interpPQ = customFit(vanTrain, radiusAbTrain,
rcond = self.interpRcond)
vanTest = self._polyvanderAuxiliary(muCTest, self.E, self.polybasis0)
DradiusAb = vanTest.dot(interpPQ)
radiusA = (radiusA
- DradiusAb[:, : - nbs].reshape(len(mus), -1, self.S).T)
radiusb = radiusb - DradiusAb[:, - nbs :].T
ff, Lf, LL = self._affineResidualMatricesContraction(radiusb, radiusA)
err = np.abs((LL - 2. * np.real(Lf) + ff) / QRHSNorm2) ** .5
return err
def getErrorEstimatorLookAhead(self, mus:Np1D,
what : str = "") -> Tuple[Np1D, List[int]]:
"""Residual estimator based on look-ahead idea."""
errTest, QTest, idxMaxEst = self._EIMStep(mus)
_approx_state_old = self.approx_state
if what == "OUTPUT" and _approx_state_old: self._approx_state = False
self.initEstimatorNormEngine()
self._approx_state = _approx_state_old
mu_muTestSample = mus[idxMaxEst]
app_muTestSample = self.getApproxReduced(mu_muTestSample)
if self._mode == RROMPy_FRAGILE:
if what == "RES" and not self.HFEngine.isCEye:
raise RROMPyException(("Cannot compute LOOK_AHEAD_RES "
"estimator in fragile mode for "
"non-scalar C."))
app_muTestSample = dot(self.trainedModel.data.projMat[:,
: app_muTestSample.shape[0]],
app_muTestSample)
else:
app_muTestSample = dot(self.samplingEngine.projectionMatrix,
app_muTestSample)
if what == "RES":
errmu = self.HFEngine.residual(mu_muTestSample, app_muTestSample,
post_c = False)
solmu = self.HFEngine.residual(mu_muTestSample, None,
post_c = False)
else:
for j, mu in enumerate(mu_muTestSample):
uEx = self.samplingEngine.nextSample(mu)
if j == 0:
solmu = emptySampleList()
solmu.reset((len(uEx), len(mu_muTestSample)),
dtype = uEx.dtype)
solmu[j] = uEx
if what == "OUTPUT" and self.approx_state:
solmu = sampleList(self.HFEngine.applyC(solmu))
app_muTestSample = sampleList(self.HFEngine.applyC(
app_muTestSample))
errmu = solmu - app_muTestSample
errsamples = (self.estimatorNormEngine.norm(errmu)
/ self.estimatorNormEngine.norm(solmu))
musT = copy(self.mus)
musT.append(mu_muTestSample)
musT = self.trainedModel.centerNormalize(musT)
musC = self.trainedModel.centerNormalize(mus)
errT = np.zeros((len(musT), len(mu_muTestSample)), dtype = np.complex)
errT[np.arange(len(self.mus), len(musT)),
np.arange(len(mu_muTestSample))] = errsamples * QTest[idxMaxEst]
vanT = self._polyvanderAuxiliary(musT, self.E + 1, self.polybasis)
fitOut = customFit(vanT, errT, full = True, rcond = self.interpRcond)
vbMng(self, "MAIN",
("Fitting {} samples with degree {} through {}... Conditioning "
"of LS system: {:.4e}.").format(len(vanT), self.E + 1,
polyfitname(self.polybasis),
fitOut[1][2][0] / fitOut[1][2][-1]), 15)
vanC = self._polyvanderAuxiliary(musC, self.E + 1, self.polybasis)
err = np.sum(np.abs(vanC.dot(fitOut[0])), axis = -1) / QTest
return err, idxMaxEst
def getErrorEstimatorNone(self, mus:Np1D) -> Np1D:
"""EIM-based residual estimator."""
err = np.max(self._EIMStep(mus, True), axis = 1)
err *= self.greedyTol / np.mean(err)
return err
def _EIMStep(self, mus:Np1D,
only_one : bool = False) -> Tuple[Np1D, Np1D, List[int]]:
"""Residual estimator based on look-ahead idea."""
mus = self.checkParameterList(mus)
tMverb, self.trainedModel.verbosity = self.trainedModel.verbosity, 0
QTest = self.trainedModel.getQVal(mus)
QTzero = np.where(QTest == 0.)[0]
if len(QTzero) > 0:
RROMPyWarning(("Adjusting estimator to avoid division by "
"numerically zero denominator."))
QTest[QTzero] = np.finfo(np.complex).eps / (1. + self.N)
QTest = np.abs(QTest)
muCTest = self.trainedModel.centerNormalize(mus)
muCTrain = self.trainedModel.centerNormalize(self.mus)
self.trainedModel.verbosity = tMverb
vanTest = self._polyvanderAuxiliary(muCTest, self.E, self.polybasis)
vanTestNext = self._polyvanderAuxiliary(muCTest, self.E + 1,
self.polybasis)[:,
vanTest.shape[1] :]
idxsTest = np.arange(vanTestNext.shape[1])
basis = np.zeros((len(idxsTest), 0), dtype = float)
idxMaxEst = []
while len(idxsTest) > 0:
vanTrial = self._polyvanderAuxiliary(muCTrain, self.E,
self.polybasis)
vanTrialNext = self._polyvanderAuxiliary(muCTrain, self.E + 1,
self.polybasis)[:,
vanTrial.shape[1] :]
vanTrial = np.hstack((vanTrial, vanTrialNext.dot(basis).reshape(
len(vanTrialNext), basis.shape[1])))
valuesTrial = vanTrialNext[:, idxsTest]
vanTestEff = np.hstack((vanTest, vanTestNext.dot(basis).reshape(
len(vanTestNext), basis.shape[1])))
vanTestNextEff = vanTestNext[:, idxsTest]
coeffTest = np.linalg.solve(vanTrial, valuesTrial)
errTest = (np.abs(vanTestNextEff - vanTestEff.dot(coeffTest))
/ np.expand_dims(QTest, 1))
if only_one: return errTest
idxMaxErr = np.unravel_index(np.argmax(errTest), errTest.shape)
idxMaxEst += [idxMaxErr[0]]
muCTrain.append(muCTest[idxMaxErr[0]])
basis = np.pad(basis, [(0, 0), (0, 1)], "constant")
basis[idxsTest[idxMaxErr[1]], -1] = 1.
idxsTest = np.delete(idxsTest, idxMaxErr[1])
return errTest, QTest, idxMaxEst
def errorEstimator(self, mus:Np1D, return_max : bool = False) -> Np1D:
"""Standard residual-based error estimator."""
setupOK = self.setupApproxLocal()
if setupOK > 0:
err = np.empty(len(mus))
err[:] = np.nan
if not return_max: return err
return err, [- setupOK], np.nan
mus = self.checkParameterList(mus)
vbMng(self.trainedModel, "INIT",
"Evaluating error estimator at mu = {}.".format(mus), 10)
if self.errorEstimatorKind == "AFFINE":
err = self.getErrorEstimatorAffine(mus)
else:
self._setupInterpolationIndices()
if self.errorEstimatorKind == "DISCREPANCY":
err = self.getErrorEstimatorDiscrepancy(mus)
elif self.errorEstimatorKind[: 10] == "LOOK_AHEAD":
err, idxMaxEst = self.getErrorEstimatorLookAhead(mus,
self.errorEstimatorKind[11 :])
else: #if self.errorEstimatorKind == "NONE":
err = self.getErrorEstimatorNone(mus)
vbMng(self.trainedModel, "DEL", "Done evaluating error estimator", 10)
if not return_max: return err
if self.errorEstimatorKind[: 10] != "LOOK_AHEAD":
idxMaxEst = np.empty(self.sampleBatchSize, dtype = int)
errCP = copy(err)
for j in range(self.sampleBatchSize):
k = np.argmax(errCP)
idxMaxEst[j] = k
if j + 1 < self.sampleBatchSize:
musZero = self.trainedModel.centerNormalize(mus, mus[k])
errCP *= np.linalg.norm(musZero.data, axis = 1)
return err, idxMaxEst, err[idxMaxEst]
def plotEstimator(self, *args, **kwargs):
super().plotEstimator(*args, **kwargs)
if self.errorEstimatorKind == "NONE":
vbMng(self, "MAIN",
("Warning! Error estimator has been arbitrarily normalized "
"before plotting."), 15)
def greedyNextSample(self, *args,
**kwargs) -> Tuple[Np1D, int, float, paramVal]:
"""Compute next greedy snapshot of solution map."""
RROMPyAssert(self._mode, message = "Cannot add greedy sample.")
self.sampleBatchIdx += 1
self.sampleBatchSize = totalDegreeN(self.npar - 1, self.sampleBatchIdx)
err, muidx, maxErr, muNext = super().greedyNextSample(*args, **kwargs)
if maxErr is not None and (np.any(np.isnan(maxErr))
or np.any(np.isinf(maxErr))):
self.sampleBatchIdx -= 1
self.sampleBatchSize = totalDegreeN(self.npar - 1,
self.sampleBatchIdx)
if (self.errorEstimatorKind == "NONE" and not np.isnan(maxErr)
and not np.isinf(maxErr)):
maxErr = None
return err, muidx, maxErr, muNext
def _setSampleBatch(self, maxS:int):
self.sampleBatchIdx, self.sampleBatchSize, S = -1, 0, 0
nextBatchSize = 1
while S + nextBatchSize <= maxS:
self.sampleBatchIdx += 1
self.sampleBatchSize = nextBatchSize
S += self.sampleBatchSize
nextBatchSize = totalDegreeN(self.npar - 1,
self.sampleBatchIdx + 1)
return S
def _preliminaryTraining(self):
"""Initialize starting snapshots of solution map."""
RROMPyAssert(self._mode, message = "Cannot start greedy algorithm.")
if self.samplingEngine.nsamples > 0: return
self._S = self._setSampleBatch(self.S)
super()._preliminaryTraining()
self.M, self.N = ("AUTO",) * 2
def setupApproxLocal(self) -> int:
"""Compute rational interpolant."""
if self.checkComputedApprox(): return -1
RROMPyAssert(self._mode, message = "Cannot setup approximant.")
self.verbosity -= 10
vbMng(self, "INIT", "Setting up local approximant.", 5)
pMat = self.samplingEngine.projectionMatrix
if self.trainedModel is not None:
pMat = pMat[:, len(self.trainedModel.data.mus) :]
self._setupTrainedModel(pMat, self.trainedModel is not None)
self.catchInstability = 2
vbDepth = getVerbosityDepth()
unstable = 0
if self.E > 0:
try:
Q = self._setupDenominator()
except RROMPyException as RE:
if RE.critical: raise RE from None
setVerbosityDepth(vbDepth)
RROMPyWarning("Downgraded {}: {}".format(RE.__class__.__name__,
RE))
unstable = 1
else:
Q = PI()
Q.coeffs = np.ones((1,) * self.npar, dtype = np.complex)
Q.npar = self.npar
Q.polybasis = self.polybasis
if not unstable:
self.trainedModel.data.Q = copy(Q)
try:
P = copy(self._setupNumerator())
except RROMPyException as RE:
if RE.critical: raise RE from None
setVerbosityDepth(vbDepth)
RROMPyWarning("Downgraded {}: {}".format(RE.__class__.__name__,
RE))
unstable = 1
if not unstable:
self.trainedModel.data.P = copy(P)
self.trainedModel.data.approxParameters = copy(
self.approxParameters)
vbMng(self, "DEL", "Done setting up local approximant.", 5)
self.catchInstability = 0
self.verbosity += 10
return unstable
def setupApprox(self, plotEst : str = "NONE") -> int:
val = super().setupApprox(plotEst)
if val == 0:
self._setupRational(self.trainedModel.data.Q,
self.trainedModel.data.P)
self.trainedModel.data.approxParameters = copy(
self.approxParameters)
return val
def loadTrainedModel(self, filename:str):
"""Load trained reduced model from file."""
super().loadTrainedModel(filename)
self._setSampleBatch(self.S + 1)

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