# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see .
#
# Copyright(C) 2013-2018 Max-Planck-Society
#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.
from __future__ import absolute_import, division, print_function
from ..compat import *
from .descent_minimizer import DescentMinimizer
from .line_search_strong_wolfe import LineSearchStrongWolfe
class RelaxedNewton(DescentMinimizer):
""" Calculates the descent direction according to a Newton scheme.
The descent direction is determined by weighting the gradient at the
current parameter position with the inverse local metric.
"""
def __init__(self, controller, line_searcher=None):
if line_searcher is None:
line_searcher = LineSearchStrongWolfe(
preferred_initial_step_size=1.)
super(RelaxedNewton, self).__init__(controller=controller,
line_searcher=line_searcher)
def get_descent_direction(self, energy):
return -energy.metric.inverse_times(energy.gradient)