relaxed_newton.py 1.68 KB
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# 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 <http://www.gnu.org/licenses/>.
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#
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# Copyright(C) 2013-2018 Max-Planck-Society
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#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.
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from __future__ import absolute_import, division, print_function
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from ..compat import *
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from .descent_minimizer import DescentMinimizer
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from .line_search_strong_wolfe import LineSearchStrongWolfe
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class RelaxedNewton(DescentMinimizer):
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    """ Calculates the descent direction according to a Newton scheme.

    The descent direction is determined by weighting the gradient at the
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    current parameter position with the inverse local metric.
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    """
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    def __init__(self, controller, line_searcher=None):
        if line_searcher is None:
            line_searcher = LineSearchStrongWolfe(
                preferred_initial_step_size=1.)
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        super(RelaxedNewton, self).__init__(controller=controller,
                                            line_searcher=line_searcher)
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    def get_descent_direction(self, energy):
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        return -energy.metric.inverse_times(energy.gradient)