# 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/>.
#
# Copyright(C) 2013-2017 Max-Planck-Society
#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.

import unittest
import numpy as np
from numpy.testing import assert_allclose
import nifty4 as ift
from itertools import product
from test.common import expand

spaces = [ift.RGSpace([1024], distances=0.123), ift.HPSpace(32)]
minimizers = [ift.SteepestDescent, ift.RelaxedNewton, ift.VL_BFGS,
              ift.ConjugateGradient, ift.NonlinearCG]


class Test_Minimizers(unittest.TestCase):

    @expand(product(minimizers, spaces))
    def test_quadratic_minimization(self, minimizer_class, space):
        np.random.seed(42)
        starting_point = ift.Field.from_random('normal', domain=space)*10
        covariance_diagonal = ift.Field.from_random(
                                  'uniform', domain=space) + 0.5
        covariance = ift.DiagonalOperator(covariance_diagonal)
        required_result = ift.Field.ones(space, dtype=np.float64)

        IC = ift.GradientNormController(tol_abs_gradnorm=1e-5)
        minimizer = minimizer_class(controller=IC)
        energy = ift.QuadraticEnergy(A=covariance, b=required_result,
                                     position=starting_point)

        (energy, convergence) = minimizer(energy)
        assert convergence == IC.CONVERGED
        assert_allclose(ift.dobj.to_global_data(energy.position.val),
                        1./ift.dobj.to_global_data(covariance_diagonal.val),
                        rtol=1e-3, atol=1e-3)