steepest_descent.py 1.46 KB
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# NIFTy
# Copyright (C) 2017  Theo Steininger
#
# Author: Theo Steininger
#
# 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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from .quasi_newton_minimizer import QuasiNewtonMinimizer


class SteepestDescent(QuasiNewtonMinimizer):
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    """Implementation of the steepest descent minimization scheme.
    
    It uses the gradient of the minimized function to get to the minimum.    
    
    Parameters
    ----------
    energy : Energy object
        The energy object providing implementations of the to be minimized
        function and gradient.
    
    Returns
    -------
    descend_direction : Field
        Returns the descent direction.
    
    """
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    def _get_descend_direction(self, energy):
        descend_direction = energy.gradient
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        norm = descend_direction.norm()
        if norm != 1:
            return descend_direction / -norm
        else:
            return descend_direction * -1