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def test_mixingcalc():
"""This test checks the basic functionality of the MixingCalculators.
The example system is based on the SinglePointCalculator test case.
"""
import numpy as np
from ase.build import fcc111
from ase.calculators.emt import EMT
from ase.calculators.mixing import SumCalculator, LinearCombinationCalculator, AverageCalculator, MixedCalculator
from ase.constraints import FixAtoms
# Calculate reference values:
atoms = fcc111('Cu', (2, 2, 1), vacuum=10.)
atoms[0].x += 0.2
# First run the test with EMT similarly to the test of the single point calculator.
calc = EMT()
atoms.calc = calc
forces = atoms.get_forces()
# SumCalculator: Alternative ways to associate a calculator with an atoms object.
atoms1 = atoms.copy()
calc1 = SumCalculator([EMT(), EMT()])
atoms1.calc = calc1
atoms2 = atoms.copy()
SumCalculator(calcs=[EMT(), EMT()], atoms=atoms2)
# Check the results.
assert np.isclose(2 * forces, atoms1.get_forces()).all()
assert np.isclose(2 * forces, atoms2.get_forces()).all()
# testing step
atoms1[0].x += 0.2
assert not np.isclose(2 * forces, atoms1.get_forces()).all()
# Check constraints
atoms1.set_constraint(FixAtoms(indices=[atom.index for atom in atoms]))
assert np.isclose(0, atoms1.get_forces()).all()
# AverageCalculator:
atoms1 = atoms.copy()
calc1 = AverageCalculator([EMT(), EMT()])
atoms1.calc = calc1
# LinearCombinationCalculator:
atoms2 = atoms.copy()
LinearCombinationCalculator([EMT(), EMT()], weights=[.5, .5], atoms=atoms2)
# Check the results (it should be the same because it is tha average of the same values).
assert np.isclose(forces, atoms1.get_forces()).all()
assert np.isclose(forces, atoms2.get_forces()).all()
# testing step
atoms1[0].x += 0.2
assert not np.isclose(2 * forces, atoms1.get_forces()).all()
try:
calc1 = LinearCombinationCalculator([], [])
except ValueError:
assert True
try:
calc1 = AverageCalculator([])
except ValueError:
assert True
# test MixedCalculator and energy contributions
w1, w2 = 0.78, 0.22
atoms1 = atoms.copy()
atoms1.calc = EMT()
E_tot = atoms1.get_potential_energy()
calc1 = MixedCalculator(EMT(), EMT(), w1, w2)
E1, E2 = calc1.get_energy_contributions(atoms1)
assert np.isclose(E1, E_tot)
assert np.isclose(E2, E_tot)
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