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damped_mass_chain.py
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Tue, May 7, 06:28

damped_mass_chain.py
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### example from Lohmann, Eid. Efficient Order Reduction of Parametric and
### Nonlinear Models by Superposition of Locally Reduced Models.
from copy import deepcopy as copy
import numpy as np
import matplotlib.pyplot as plt
from rrompy.reduction_methods import (NearestNeighbor as NN,
RationalInterpolant as RI,
RationalInterpolantGreedy as RIG,
RationalInterpolantPivoted as RIP,
RationalInterpolantGreedyPivoted as RIGP)
from rrompy.parameter.parameter_sampling import (QuadratureSampler as QS,
EmptySampler as ES)
from damped_mass_chain_engine import (bode as bode0, bodeLog, MassChainEngine,
MassChainEngineLog, AugmentedMassChainEngine, AugmentedMassChainEngineLog)
from rrompy.utilities.base.decorators import addWhiteNoise
##########################
fullModelOrder = 1 #+ 1
SMarginal = 1 #* 2
state = 0 #+ 1
noise_level = 0 #+ 1e-5
LS = 0 #+ 6
##########################
modelSign = "Surrogate modeling for frequency response of "
if fullModelOrder == 1: modelSign += "augmented "
modelSign += "damper-mass-spring model"
if SMarginal > 1: modelSign += " with 1 design parameter"
modelSign += ".\nOutput is "
if state:
modelSign += "vector of mass displacements. "
else:
modelSign += "displacement of last mass. "
if LS:
modelSign += "Least-squares: S - N - 1 = {}. ".format(LS)
else:
modelSign += "Interpolatory: S = N + 1. "
modelSign += "Noise level: {}.\n".format(noise_level)
print(modelSign)
M = [np.array([1., 5., 25., 125.])]
N = len(M[0])
D = [np.zeros((N, N))]
D[0][0, 1], D[0][1, 2], D[0][2, 3], D[0][3, 3] = .1, .4, 1.6, 0.
D[0] = D[0] + D[0].T
K = [np.zeros((N, N))]
K[0][0, 1], K[0][1, 2], K[0][2, 3], K[0][0, 3], K[0][3, 3] = 9., 3., 1., 1., 2.
K[0] = K[0] + K[0].T
B = np.append(27., np.zeros(N - 1)).reshape(-1, 1)
if SMarginal > 1:
M += [np.zeros(N)]
D += [np.zeros((N, N))]
D[1][3, 3] = 1.
D[1] = D[1] + D[1].T
K += [np.zeros((N, N))]
K[1][0, 3], K[1][3, 3] = 2., 2.
K[1] = K[1] + K[1].T
if state:
C = np.eye(4)
else:
C = np.append(np.zeros(N - 1), 1.).reshape(1, -1)
for logspace in range(2):
print("Approximation in l{}space".format("og" * logspace
+ "in" * (not logspace)))
if logspace:
bode = bodeLog
if fullModelOrder == 1:
engine = AugmentedMassChainEngineLog
else:
engine = MassChainEngineLog
else:
bode = bode0
if fullModelOrder == 1:
engine = AugmentedMassChainEngine
else:
engine = MassChainEngine
solver = addWhiteNoise(noise_level)(engine)(M, D, K, B, C)
ss, mu = [1e-2, 1e1], []
s0 = 10. ** np.mean(np.log10(ss))
freq = np.logspace(np.log10(ss[0]), np.log10(ss[1]), 100)
if logspace:
ss, freq = [np.log10(ss[0]), np.log10(ss[1])], np.log10(freq)
s0, parameterMap = np.log10(s0), 1.
else:
parameterMap = {"F": [("log10", "x")], "B": [(10., "**", "x")]}
krange = [[ss[0]], [ss[-1]]]
k0, srange = [s0], copy(krange)
if SMarginal > 1:
ms = [0., 1.]
m0, mrange = np.mean(ms), [[ms[0]], [ms[-1]]]
krange[0] += mrange[0]
krange[1] += mrange[1]
k0 += [m0]
mu = [.5 * (ms[1] - ms[0]) / (SMarginal - 1)]
if not logspace:
parameterMap["F"] += [("x")]
parameterMap["B"] += [("x")]
for method in ["RI", "RI_GREEDY"]:
print("Testing {} method".format(method))
if method == "RI":
params = {'S':15, 'POD':True, 'polybasis':"CHEBYSHEV"}
if LS: params["N"] = params["S"] - 1 - LS
if SMarginal > 1:
algo = RIP
else:
params['sampler'] = QS(srange, "CHEBYSHEV", parameterMap)
algo = RI
if method == "RI_GREEDY":
params = {'S':5, 'POD':True, 'polybasis':"LEGENDRE",
'greedyTol':1e-2, 'errorEstimatorKind':"DISCREPANCY",
'trainSetGenerator':QS(srange, "CHEBYSHEV",
parameterMap)}
if SMarginal > 1:
algo = RIGP
else:
params['sampler'] = QS(srange, "UNIFORM", parameterMap)
algo = RIG
if SMarginal > 1:
params["paramsMarginal"] = {"MMarginal": SMarginal - 1}
params['SMarginal'] = SMarginal
params['polybasisMarginal'] = "MONOMIAL"
params['radialDirectionalWeightsMarginal'] = [2. / (ms[1] - ms[0])]
params['matchingWeight'] = 1.
params['samplerPivot'] = QS(srange, "UNIFORM", parameterMap)
params['samplerMarginal'] = QS(mrange, "UNIFORM")
approx = algo([0], solver, mu0 = k0, approx_state = True,
approxParameters = params, verbosity = 5,
storeAllSamples = True)
else:
approx = algo(solver, mu0 = k0, approx_state = True,
approxParameters = params, verbosity = 5)
if "GREEDY" in method:
approx.setupApprox("LAST")
else:
approx.setupApprox()
approxNN = NN(solver, mu0 = k0, approx_state = True, verbosity = 5,
approxParameters = {'S':len(approx.mus),
'POD':params['POD'], 'sampler':ES()})
if SMarginal > 1:
approxNN.setSamples(approx.storedSamplesFilenames)
approx.purgeStoredSamples()
for m in approx.musMarginal:
bode(freq, m[0],
[approx.getHF, approx.getApprox, approxNN.getApprox])
else:
approxNN.setSamples(approx.samplingEngine)
bode(freq, mu, [approx.getHF, approx.getApprox, approxNN.getApprox])
if SMarginal > 1:
bode(freq, [1.5 * ms[1]],
[approx.getHF, approx.getApprox, approxNN.getApprox])
bode(freq, [2. * ms[1]],
[approx.getHF, approx.getApprox, approxNN.getApprox])
verb = approx.verbosity
approx.verbosity = 0
mspace = np.linspace(ms[0], ms[-1], 10)
for j, t in enumerate(mspace):
pls = approx.getPoles([None, t])
if j == 0:
poles = np.empty((len(mspace), len(pls)),
dtype = np.complex)
poles[j] = pls
for j, t in enumerate(approx.musMarginal):
pls = approx.getPoles([None, t[0][0]])
if j == 0:
polesE = np.empty((SMarginal, len(pls)),
dtype = np.complex)
polesE[j] = pls
approx.verbosity = verb
fig = plt.figure(figsize = (10, 6))
ax = fig.add_subplot(1, 1, 1)
ax.plot(np.real(poles), np.imag(poles), '--')
ax.plot(np.real(polesE), np.imag(polesE), 'ko', markersize = 4)
ax.set_xlabel('Real')
ax.set_ylabel('Imag')
ax.grid()
plt.show()
else:
poles = approx.getPoles()
print("Poles:\n{}".format(poles))
print("\n")

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