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# fmt: off
import numpy as np
import pytest
from ase.build import molecule
from ase.constraints import FixCartesian
@pytest.fixture()
def atoms():
return molecule('CH3CH2OH')
def test_fixcartesian_misc():
mask = np.array([1, 1, 0], bool)
indices = [2, 3]
constraint = FixCartesian(indices, mask=mask)
assert '3' in str(constraint)
dct = constraint.todict()['kwargs']
assert dct['a'] == indices
assert all(dct['mask'] == mask)
# 2 atoms x 2 directions == 4 DOFs constrained
assert constraint.get_removed_dof(atoms=None) == 4 # XXX atoms
def test_fixcartesian_adjust(atoms):
cart_mask = np.array([False, True, True])
atom_index = [2, 3, 5, 6] # Arbitrary subset of atoms
fixmask = np.zeros((len(atoms), 3), bool)
fixmask[atom_index] = cart_mask[None, :]
oldpos = atoms.get_positions()
constraint = FixCartesian(atom_index, mask=cart_mask)
rng = np.random.RandomState(42)
deviation = 1.0 + rng.random((len(atoms), 3))
newpos = oldpos + deviation
constraint.adjust_positions(atoms, newpos)
newpos_expected = oldpos + deviation
newpos_expected[fixmask] = oldpos[fixmask]
assert newpos == pytest.approx(newpos_expected, abs=1e-14)
oldforces = 1.0 + rng.random((len(atoms), 3))
newforces = oldforces.copy()
constraint.adjust_forces(atoms, newforces)
newforces_expected = oldforces.copy()
newforces_expected[fixmask] = 0.0
assert newforces == pytest.approx(newforces_expected, abs=1e-14)
nzeros = sum(abs(newforces_expected.ravel()) < 1e-14)
ndof = constraint.get_removed_dof(atoms)
assert nzeros == ndof == sum(cart_mask) * len(atom_index)
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