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import numpy as np
import pytest
from ase.build import bulk
from ase.constraints import FixAtoms, UnitCellFilter
from ase.calculators.emt import EMT
from ase.optimize.precon import make_precon, Precon
from ase.neighborlist import neighbor_list
from ase.utils.ff import Bond
@pytest.fixture
def ref_atoms():
atoms = bulk('Al', a=3.994) * 2
atoms.calc = EMT()
i, j, r = neighbor_list('ijd', atoms, cutoff=3.0)
bonds = [Bond(I, J, k=1.0, b0=R) for (I, J, R) in zip(i, j, r)]
return atoms, bonds
@pytest.fixture
def atoms(ref_atoms):
atoms, bonds = ref_atoms
atoms.rattle(stdev=0.1, seed=7)
return atoms, bonds
@pytest.fixture
def var_cell(atoms):
atoms, bonds = atoms
return UnitCellFilter(atoms), bonds
@pytest.fixture
def fixed_atoms(atoms):
atoms, bonds = atoms
atoms.set_constraint(FixAtoms(indices=[0]))
return atoms, bonds
def check_assembly(precon, system):
atoms, bonds = system
kwargs = {}
if precon == 'FF' or precon == 'Exp_FF':
kwargs['bonds'] = bonds
precon = make_precon(precon, atoms, **kwargs)
assert isinstance(precon, Precon)
# check its a symmetric positive definite matrix of expected size
N = 3 * len(atoms)
P = precon.asarray()
assert P.shape == (N, N)
assert np.abs(P - P.T).max() < 1e-6
assert np.all(np.linalg.eigvalsh(P)) > 0
precons = [None, 'C1', 'Exp', 'Pfrommer', 'FF', 'Exp_FF']
@pytest.mark.parametrize('precon', precons)
def test_assembly_ref_atoms(precon, ref_atoms):
check_assembly(precon, ref_atoms)
@pytest.mark.parametrize('precon', precons)
def test_assembly_atoms(precon, atoms):
check_assembly(precon, atoms)
@pytest.mark.parametrize('precon', precons)
def test_assembly_var_cell(precon, var_cell):
check_assembly(precon, var_cell)
@pytest.mark.parametrize('precon', precons)
def test_assembly_fixed_atoms(precon, fixed_atoms):
check_assembly(precon, fixed_atoms)
def check_apply(precon, system):
atoms, bonds = system
kwargs = {}
if precon == 'FF' or precon == 'Exp_FF':
kwargs['bonds'] = bonds
precon = make_precon(precon, atoms, **kwargs)
forces = atoms.get_forces().reshape(-1)
precon_forces, residual = precon.apply(forces, atoms)
residual_P = np.linalg.norm(precon_forces, np.inf)
print(f'|F| = {residual:.3f} '
f'|F|_P = {np.linalg.norm(precon_forces, np.inf):.3f}')
# force norm should not get much bigger when we precondition:
# in this case all norms get smaller, but this will not be true in general
assert residual_P <= residual
# forces on any fixed atoms be zero, and remain zero after applying precon
fixed_atoms = []
for constraint in atoms.constraints:
if isinstance(constraint, FixAtoms):
fixed_atoms.extend(list(constraint.index))
if len(fixed_atoms) != 0:
assert np.linalg.norm(forces[fixed_atoms], np.inf) < 1e-8
assert np.linalg.norm(precon_forces[fixed_atoms], np.inf) < 1e-8
@pytest.mark.parametrize('precon', precons)
def test_apply_atoms(precon, atoms):
check_apply(precon, atoms)
@pytest.mark.parametrize('precon', precons)
def test_apply_fixed_atoms(precon, fixed_atoms):
check_apply(precon, fixed_atoms)
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