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__init__.py
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# -*- mode:python; coding: utf-8 -*-
# @file
# @section LICENSE
#
# Copyright (©) 2016-2020 EPFL (École Polytechnique Fédérale de Lausanne),
# Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
"""
Pulling solvers to nonlinear_solvers module
"""
from sys import stderr
from functools import wraps
import numpy as np
from scipy.sparse.linalg import LinearOperator, lgmres
from scipy.linalg import norm
from scipy.optimize import newton_krylov, root
from .. import EPSolver, Logger, LogLevel
__all__ = ['NLNoConvergence',
'DFSANESolver',
'NewtonKrylovSolver',
'ToleranceManager']
class NLNoConvergence(Exception):
"""Convergence not reached exception"""
class NewtonRaphsonSolver(EPSolver):
"""
Newton-Raphson based on CTO
"""
def __init__(self, residual, model):
super(NewtonRaphsonSolver, self).__init__(residual)
self.model = model
self._residual = self.getResidual()
self._x = self.getStrainIncrement()
self.last_solution = np.zeros_like(self._x)
def applyTangent(self, _input, strain):
_input = np.reshape(_input, strain.shape)
out = np.zeros_like(_input)
self._residual.applyTangent(out, _input, strain)
return out
def solve(self):
self._x[...] = 0
# For initial guess, compute the strain due to boundary tractions
self._residual.computeResidual(self._x)
self._x[...] = self._residual.getVector()
res_vec = np.ravel(self._residual.getVector())
initial_norm = norm(res_vec)
self._residual.computeResidual(self._x)
n_max = 100
i = 0
while norm(res_vec) / initial_norm > 1e-10 and i < n_max:
# Making linear tangent
tangent = LinearOperator(
(self._x.size, self._x.size),
matvec=lambda x: self.applyTangent(x, self._x))
res_vec *= -1
correction, ok = lgmres(tangent, res_vec, tol=1e-12, maxiter=100)
if ok != 0:
raise Exception("LGMRES not converged")
self._x += np.reshape(correction, self._x.shape)
self._residual.computeResidual(self._x)
i += 1
Logger().get(LogLevel.info) << \
"Solved Newton-Raphson in {} iterations".format(i)
# Computing the strain correction
self.last_solution *= -1
self.last_solution += self._x
# Computing displacements
self._residual.computeResidualDisplacement(self.last_solution)
self.last_solution[...] = self._x[...]
class ScipySolver(EPSolver):
"""
Base class for solvers wrapping SciPy routines
"""
def __init__(self, residual, model, callback=None):
super(ScipySolver, self).__init__(residual)
self.model = model
self.callback = callback
self._x = self.getStrainIncrement()
self._residual = self.getResidual()
self.options = {'ftol': 0, 'fatol': 1e-9}
@property
def tolerance(self):
"Return solver absolute tolerance"
return self.options['fatol']
@tolerance.setter
def tolerance(self, v):
"Set solver absolute tolerance"
self.options['fatol'] = v
def solve(self):
"""
Solve the nonlinear plasticity equation using the scipy_solve routine
"""
# For initial guess, compute the strain due to boundary tractions
# self._residual.computeResidual(self._x)
# self._x[...] = self._residual.getVector()
# Scipy root callback
def compute_residual(x):
self._residual.computeResidual(x)
return self._residual.getVector().copy()
# Solve
self._x[...] = self.scipy_solve(compute_residual)
# Computing displacements
self._residual.computeResidualDisplacement(self._x)
def reset(self):
self._x[...] = 0
class NewtonKrylovSolver(ScipySolver):
"""
Solve using a finite-difference Newton-Krylov method
"""
def __init__(self, residual, model, callback=None):
ScipySolver.__init__(self, residual, model, callback)
def scipy_solve(self, compute_residual):
"Solve R(delta epsilon) = 0 using a newton-krylov method"
try:
return newton_krylov(compute_residual, self._x,
f_tol=self.options['fatol'],
verbose=True, callback=self.callback)
except Exception as e:
raise NLNoConvergence(e.what())
class DFSANESolver(ScipySolver):
"""
Solve using a spectral residual jacobianless method
"""
def __init__(self, residual, model, callback=None):
ScipySolver.__init__(self, residual, model, callback)
def scipy_solve(self, compute_residual):
"Solve R(delta epsilon) = 0 using a df-sane method"
solution = root(compute_residual,
self._x,
method='df-sane',
options=self.options,
callback=self.callback)
Logger().get(LogLevel.info) << \
"DF-SANE: {} ({} iterations, {})".format(
solution.message,
solution.nit,
self.options)
if not solution.success:
raise NLNoConvergence("DF-SANE did not converge")
return solution.x.copy()
def ToleranceManager(start, end, rate, key='fatol'):
"Decorator to manage tolerance of non-linear solver"
start /= rate # just anticipating first multiplication
def actual_decorator(cls):
orig_init = cls.__init__
orig_solve = cls.scipy_solve
orig_update_state = cls.updateState
@wraps(cls.__init__)
def __init__(obj, *args, **kwargs):
orig_init(obj, *args, **kwargs)
obj.options[key] = start
@wraps(cls.scipy_solve)
def scipy_solve(obj, *args, **kwargs):
ftol = obj.options[key]
ftol *= rate
obj.options[key] = max(ftol, end)
return orig_solve(obj, *args, **kwargs)
@wraps(cls.updateState)
def updateState(obj, *args, **kwargs):
obj.options[key] = start
return orig_update_state(obj, *args, **kwargs)
cls.__init__ = __init__
cls.scipy_solve = scipy_solve
cls.updateState = updateState
return cls
return actual_decorator

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