def test_cms(self):
parts = self.system.part[:]
g = GalileiTransform()
total_mass = np.sum(parts.mass)
com = np.sum(np.multiply(parts.mass.reshape((-1, 1)), parts.pos),
axis=0) / total_mass
np.testing.assert_allclose(np.copy(g.system_CMS()), com)
def test_galilei_transform(self):
g = GalileiTransform()
no_virtual = self.system.part.select(virtual=False)
# Center of mass
np.testing.assert_allclose(
np.copy(g.system_CMS()),
np.average(no_virtual.pos, weights=no_virtual.mass, axis=0))
# Center of mass velocity
np.testing.assert_allclose(
np.copy(g.system_CMS_velocity()),
np.average(no_virtual.v, weights=no_virtual.mass, axis=0))