# 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 .
from .quasi_newton_minimizer import QuasiNewtonMinimizer
class SteepestDescent(QuasiNewtonMinimizer):
"""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.
"""
def _get_descend_direction(self, energy):
descend_direction = energy.gradient
norm = descend_direction.norm()
if norm != 1:
return descend_direction / -norm
else:
return descend_direction * -1