Пример #1
0
def exercise_linear_velocity_manipulations(tardy_model):
    for nosiet in [None, tardy_model.number_of_sites_in_each_tree()]:
        tardy_model.assign_random_velocities(e_kin_target=17)
        if (tardy_model.degrees_of_freedom == 0):
            assert approx_equal(tardy_model.e_kin(), 0)
            assert tardy_model.mean_linear_velocity(
                number_of_sites_in_each_tree=None) is None
        else:
            assert approx_equal(tardy_model.e_kin(), 17)
            mlv = tardy_model.mean_linear_velocity(
                number_of_sites_in_each_tree=nosiet)
            if (mlv is not None):
                assert is_above_limit(value=abs(mlv), limit=1e-3)
                tardy_model.subtract_from_linear_velocities(
                    number_of_sites_in_each_tree=nosiet, value=mlv)
                mlv = tardy_model.mean_linear_velocity(
                    number_of_sites_in_each_tree=nosiet)
                assert approx_equal(mlv, (0, 0, 0))
Пример #2
0
def exercise_linear_velocity_manipulations(tardy_model):
  for nosiet in [None, tardy_model.number_of_sites_in_each_tree()]:
    tardy_model.assign_random_velocities(e_kin_target=17)
    if (tardy_model.degrees_of_freedom == 0):
      assert approx_equal(tardy_model.e_kin(), 0)
      assert tardy_model.mean_linear_velocity(
        number_of_sites_in_each_tree=None) is None
    else:
      assert approx_equal(tardy_model.e_kin(), 17)
      mlv = tardy_model.mean_linear_velocity(
        number_of_sites_in_each_tree=nosiet)
      if (mlv is not None):
        assert is_above_limit(value=abs(mlv), limit=1e-3)
        tardy_model.subtract_from_linear_velocities(
          number_of_sites_in_each_tree=nosiet, value=mlv)
        mlv = tardy_model.mean_linear_velocity(
          number_of_sites_in_each_tree=nosiet)
        assert approx_equal(mlv, (0,0,0))
def run_call_back(flags, space_group_info):
    structure = set_up_random_structure(space_group_info)
    if (flags.Verbose):
        structure.scattering_type_registry().show()
    rho_at_sites_from_phenix_fft_map = map_value_at_sites(structure)
    rho_at_sites_calculated = map_value_at_sites_calculated(structure)
    for scatterer, rf, rc in zip(structure.scatterers(),
                                 rho_at_sites_from_phenix_fft_map,
                                 rho_at_sites_calculated):
        if (flags.Verbose):
            print numstr(scatterer.site), "%.3f" % rf, "%.3f" % rc
    from scitbx.array_family import flex
    corr = flex.linear_correlation(
        flex.double(rho_at_sites_from_phenix_fft_map),
        flex.double(rho_at_sites_calculated))
    assert corr.is_well_defined
    cc = corr.coefficient()
    if (flags.Verbose):
        print "Correlation coefficient:", cc
    from libtbx.test_utils import is_above_limit
    assert is_above_limit(value=cc, limit=0.99)
    if (flags.Verbose):
        print
def run_call_back(flags, space_group_info):
  structure = set_up_random_structure(space_group_info)
  if (flags.Verbose):
    structure.scattering_type_registry().show()
  rho_at_sites_from_phenix_fft_map = map_value_at_sites(structure)
  rho_at_sites_calculated = map_value_at_sites_calculated(structure)
  for scatterer,rf,rc in zip(
        structure.scatterers(),
        rho_at_sites_from_phenix_fft_map,
        rho_at_sites_calculated):
     if (flags.Verbose):
       print numstr(scatterer.site), "%.3f" % rf, "%.3f" % rc
  from scitbx.array_family import flex
  corr = flex.linear_correlation(
    flex.double(rho_at_sites_from_phenix_fft_map),
    flex.double(rho_at_sites_calculated))
  assert corr.is_well_defined
  cc = corr.coefficient()
  if (flags.Verbose):
    print "Correlation coefficient:", cc
  from libtbx.test_utils import is_above_limit
  assert is_above_limit(value=cc, limit=0.99)
  if (flags.Verbose):
    print
Пример #5
0
def compare_essence_and_fast_tardy_models(etm,
                                          have_singularity=False,
                                          run_minimization=False):
    etm = scitbx.rigid_body.essence.tardy.model(  # new instance to reset q, qd
        labels=etm.labels,
        sites=etm.sites,
        masses=etm.masses,
        tardy_tree=etm.tardy_tree,
        potential_obj=etm.potential_obj,
        near_singular_hinges_angular_tolerance_deg=etm.
        near_singular_hinges_angular_tolerance_deg)
    ftm = etm_as_ftm(etm=etm)
    #
    assert list(ftm.root_indices()) == etm.root_indices()
    #
    q_packed_zero = etm.pack_q()
    qd_packed_zero = etm.pack_qd()

    #
    def check_packed():
        e = etm.pack_q()
        f = ftm.pack_q()
        assert approx_equal(e, f)
        e = etm.pack_qd()
        f = ftm.pack_qd()
        assert approx_equal(e, f)

    check_packed()
    mt = flex.mersenne_twister(seed=0)
    q_packed_rand = mt.random_double(size=q_packed_zero.size()) * 2 - 1
    qd_packed_rand = mt.random_double(size=qd_packed_zero.size()) * 2 - 1
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_zero)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_zero)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_rand)
    check_packed()
    #
    fnosiet = ftm.number_of_sites_in_each_tree()
    assert list(fnosiet) == etm.number_of_sites_in_each_tree()
    e = etm.sum_of_masses_in_each_tree()
    f = ftm.sum_of_masses_in_each_tree()
    assert approx_equal(e, f)

    #
    def check_mean_linear_velocity():
        e = etm.mean_linear_velocity(number_of_sites_in_each_tree=None)
        for f in [
                ftm.mean_linear_velocity(number_of_sites_in_each_tree=None),
                ftm.mean_linear_velocity(number_of_sites_in_each_tree=fnosiet)
        ]:
            if (e is None): assert f is None
            else: assert approx_equal(e, f)

    check_mean_linear_velocity()
    value = matrix.col(mt.random_double(size=3) * 2 - 1)
    for tm in [etm, ftm]:
        tm.subtract_from_linear_velocities(number_of_sites_in_each_tree=None,
                                           value=value)
    check_mean_linear_velocity()
    for tm in [etm, ftm]:
        tm.subtract_from_linear_velocities(
            number_of_sites_in_each_tree=fnosiet, value=value)
    check_mean_linear_velocity()
    #
    e = etm.sites_moved()
    f = ftm.sites_moved()
    assert approx_equal(e, f)
    e = etm.e_pot()
    f = ftm.e_pot()
    assert approx_equal(e, f)
    e = etm.d_e_pot_d_sites()
    f = ftm.d_e_pot_d_sites()
    assert approx_equal(e, f)
    e = etm.d_e_pot_d_q_packed()
    f = ftm.d_e_pot_d_q_packed()
    if (e.size() == 0):
        assert f.size() == 0
    else:
        e_max_abs = flex.max(flex.abs(e))
        if (etm.potential_obj is None):
            assert is_below_limit(value=e_max_abs, limit=1e-10)
        else:
            # note: e_max_abs is random generator dependent
            # by change much smaller e_max_abs are possible
            assert is_above_limit(value=e_max_abs, limit=0.1)
        assert approx_equal(e, f)
    #
    e = etm.e_kin()
    f = ftm.e_kin()
    assert approx_equal(e, f)
    e = etm.e_tot()
    f = ftm.e_tot()
    assert approx_equal(e, f)
    etm.reset_e_kin(e_kin_target=1.234)
    ftm.reset_e_kin(e_kin_target=1.234)
    e = etm.e_kin()
    if (etm.degrees_of_freedom == 0):
        assert approx_equal(e, 0)
    else:
        assert approx_equal(e, 1.234)
    f = ftm.e_kin()
    assert approx_equal(e, f)
    try:
        ftm.reset_e_kin(e_kin_target=1, e_kin_epsilon=0)
    except RuntimeError, e:
        assert str(e).find("e_kin_epsilon > 0") > 0
Пример #6
0
def compare_essence_and_fast_tardy_models(
      etm,
      have_singularity=False,
      run_minimization=False):
  etm = scitbx.rigid_body.essence.tardy.model( # new instance to reset q, qd
    labels=etm.labels,
    sites=etm.sites,
    masses=etm.masses,
    tardy_tree=etm.tardy_tree,
    potential_obj=etm.potential_obj,
    near_singular_hinges_angular_tolerance_deg=
      etm.near_singular_hinges_angular_tolerance_deg)
  ftm = etm_as_ftm(etm=etm)
  #
  assert list(ftm.root_indices()) == etm.root_indices()
  #
  q_packed_zero = etm.pack_q()
  qd_packed_zero = etm.pack_qd()
  #
  def check_packed():
    e = etm.pack_q()
    f = ftm.pack_q()
    assert approx_equal(e, f)
    e = etm.pack_qd()
    f = ftm.pack_qd()
    assert approx_equal(e, f)
  check_packed()
  mt = flex.mersenne_twister(seed=0)
  q_packed_rand = mt.random_double(size=q_packed_zero.size())*2-1
  qd_packed_rand = mt.random_double(size=qd_packed_zero.size())*2-1
  for tm in [etm, ftm]: tm.unpack_q(q_packed=q_packed_rand)
  check_packed()
  for tm in [etm, ftm]: tm.unpack_q(q_packed=q_packed_zero)
  check_packed()
  for tm in [etm, ftm]: tm.unpack_qd(qd_packed=qd_packed_rand)
  check_packed()
  for tm in [etm, ftm]: tm.unpack_qd(qd_packed=qd_packed_zero)
  check_packed()
  for tm in [etm, ftm]: tm.unpack_q(q_packed=q_packed_rand)
  check_packed()
  for tm in [etm, ftm]: tm.unpack_qd(qd_packed=qd_packed_rand)
  check_packed()
  #
  fnosiet = ftm.number_of_sites_in_each_tree()
  assert list(fnosiet) == etm.number_of_sites_in_each_tree()
  e = etm.sum_of_masses_in_each_tree()
  f = ftm.sum_of_masses_in_each_tree()
  assert approx_equal(e, f)
  #
  def check_mean_linear_velocity():
    e = etm.mean_linear_velocity(number_of_sites_in_each_tree=None)
    for f in [ftm.mean_linear_velocity(number_of_sites_in_each_tree=None),
              ftm.mean_linear_velocity(number_of_sites_in_each_tree=fnosiet)]:
      if (e is None): assert f is None
      else:           assert approx_equal(e, f)
  check_mean_linear_velocity()
  value = matrix.col(mt.random_double(size=3)*2-1)
  for tm in [etm, ftm]:
    tm.subtract_from_linear_velocities(
      number_of_sites_in_each_tree=None,
      value=value)
  check_mean_linear_velocity()
  for tm in [etm, ftm]:
    tm.subtract_from_linear_velocities(
      number_of_sites_in_each_tree=fnosiet,
      value=value)
  check_mean_linear_velocity()
  #
  e = etm.sites_moved()
  f = ftm.sites_moved()
  assert approx_equal(e, f)
  e = etm.e_pot()
  f = ftm.e_pot()
  assert approx_equal(e, f)
  e = etm.d_e_pot_d_sites()
  f = ftm.d_e_pot_d_sites()
  assert approx_equal(e, f)
  e = etm.d_e_pot_d_q_packed()
  f = ftm.d_e_pot_d_q_packed()
  if (e.size() == 0):
    assert f.size() == 0
  else:
    e_max_abs = flex.max(flex.abs(e))
    if (etm.potential_obj is None):
      assert is_below_limit(value=e_max_abs, limit=1e-10)
    else:
      # note: e_max_abs is random generator dependent
      # by change much smaller e_max_abs are possible
      assert is_above_limit(value=e_max_abs, limit=0.1)
    assert approx_equal(e, f)
  #
  e = etm.e_kin()
  f = ftm.e_kin()
  assert approx_equal(e, f)
  e = etm.e_tot()
  f = ftm.e_tot()
  assert approx_equal(e, f)
  etm.reset_e_kin(e_kin_target=1.234)
  ftm.reset_e_kin(e_kin_target=1.234)
  e = etm.e_kin()
  if (etm.degrees_of_freedom == 0):
    assert approx_equal(e, 0)
  else:
    assert approx_equal(e, 1.234)
  f = ftm.e_kin()
  assert approx_equal(e, f)
  try:
    ftm.reset_e_kin(e_kin_target=1, e_kin_epsilon=0)
  except RuntimeError, e:
    assert str(e).find("e_kin_epsilon > 0") > 0
Пример #7
0
Файл: tst.py Проект: dials/cctbx
def compare_essence_and_fast_tardy_models(etm,
                                          have_singularity=False,
                                          run_minimization=False):
    etm = scitbx.rigid_body.essence.tardy.model(  # new instance to reset q, qd
        labels=etm.labels,
        sites=etm.sites,
        masses=etm.masses,
        tardy_tree=etm.tardy_tree,
        potential_obj=etm.potential_obj,
        near_singular_hinges_angular_tolerance_deg=etm.
        near_singular_hinges_angular_tolerance_deg)
    ftm = etm_as_ftm(etm=etm)
    #
    assert list(ftm.root_indices()) == etm.root_indices()
    #
    q_packed_zero = etm.pack_q()
    qd_packed_zero = etm.pack_qd()

    #
    def check_packed():
        e = etm.pack_q()
        f = ftm.pack_q()
        assert approx_equal(e, f)
        e = etm.pack_qd()
        f = ftm.pack_qd()
        assert approx_equal(e, f)

    check_packed()
    mt = flex.mersenne_twister(seed=0)
    q_packed_rand = mt.random_double(size=q_packed_zero.size()) * 2 - 1
    qd_packed_rand = mt.random_double(size=qd_packed_zero.size()) * 2 - 1
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_zero)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_zero)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_q(q_packed=q_packed_rand)
    check_packed()
    for tm in [etm, ftm]:
        tm.unpack_qd(qd_packed=qd_packed_rand)
    check_packed()
    #
    fnosiet = ftm.number_of_sites_in_each_tree()
    assert list(fnosiet) == etm.number_of_sites_in_each_tree()
    e = etm.sum_of_masses_in_each_tree()
    f = ftm.sum_of_masses_in_each_tree()
    assert approx_equal(e, f)

    #
    def check_mean_linear_velocity():
        e = etm.mean_linear_velocity(number_of_sites_in_each_tree=None)
        for f in [
                ftm.mean_linear_velocity(number_of_sites_in_each_tree=None),
                ftm.mean_linear_velocity(number_of_sites_in_each_tree=fnosiet)
        ]:
            if (e is None): assert f is None
            else: assert approx_equal(e, f)

    check_mean_linear_velocity()
    value = matrix.col(mt.random_double(size=3) * 2 - 1)
    for tm in [etm, ftm]:
        tm.subtract_from_linear_velocities(number_of_sites_in_each_tree=None,
                                           value=value)
    check_mean_linear_velocity()
    for tm in [etm, ftm]:
        tm.subtract_from_linear_velocities(
            number_of_sites_in_each_tree=fnosiet, value=value)
    check_mean_linear_velocity()
    #
    e = etm.sites_moved()
    f = ftm.sites_moved()
    assert approx_equal(e, f)
    e = etm.e_pot()
    f = ftm.e_pot()
    assert approx_equal(e, f)
    e = etm.d_e_pot_d_sites()
    f = ftm.d_e_pot_d_sites()
    assert approx_equal(e, f)
    e = etm.d_e_pot_d_q_packed()
    f = ftm.d_e_pot_d_q_packed()
    if (e.size() == 0):
        assert f.size() == 0
    else:
        e_max_abs = flex.max(flex.abs(e))
        if (etm.potential_obj is None):
            assert is_below_limit(value=e_max_abs, limit=1e-10)
        else:
            # note: e_max_abs is random generator dependent
            # by change much smaller e_max_abs are possible
            assert is_above_limit(value=e_max_abs, limit=0.1)
        assert approx_equal(e, f)
    #
    e = etm.e_kin()
    f = ftm.e_kin()
    assert approx_equal(e, f)
    e = etm.e_tot()
    f = ftm.e_tot()
    assert approx_equal(e, f)
    etm.reset_e_kin(e_kin_target=1.234)
    ftm.reset_e_kin(e_kin_target=1.234)
    e = etm.e_kin()
    if (etm.degrees_of_freedom == 0):
        assert approx_equal(e, 0)
    else:
        assert approx_equal(e, 1.234)
    f = ftm.e_kin()
    assert approx_equal(e, f)
    try:
        ftm.reset_e_kin(e_kin_target=1, e_kin_epsilon=0)
    except RuntimeError as e:
        assert str(e).find("e_kin_epsilon > 0") > 0
    else:
        raise Exception_expected
    etm.assign_zero_velocities()
    ftm.assign_zero_velocities()
    assert etm.e_kin() == 0
    assert ftm.e_kin() == 0
    random.seed(0)
    etm.assign_random_velocities()
    random.seed(0)
    ftm.assign_random_velocities()
    e = etm.e_kin()
    f = ftm.e_kin()
    assert approx_equal(e, f)
    #
    mt = flex.mersenne_twister(seed=0)
    qdd_rand_array = []
    for body in etm.bodies:
        qdd_rand_array.append(
            matrix.col(
                mt.random_double(size=body.joint.degrees_of_freedom) * 2 - 1))
    tau_rand_array = []
    for body in etm.bodies:
        tau_rand_array.append(
            matrix.col(
                mt.random_double(size=body.joint.degrees_of_freedom) * 2 - 1))
    f_ext_rand_array = []
    for ib in range(len(etm.bodies)):
        f_ext_rand_array.append(matrix.col(mt.random_double(size=6) * 2 - 1))
    grav_accn_rand = matrix.col(mt.random_double(size=6) * 2 - 1)

    def pack_array(array, packed_size=None):
        result = flex.double()
        if (packed_size is not None):
            result.reserve(packed_size)
        for sub in array:
            result.extend(flex.double(sub))
        if (packed_size is not None):
            assert result.size() == packed_size
        return result

    qdd_rand_packed = pack_array(array=qdd_rand_array,
                                 packed_size=etm.degrees_of_freedom)
    tau_rand_packed = pack_array(array=tau_rand_array,
                                 packed_size=etm.degrees_of_freedom)
    f_ext_rand_packed = pack_array(array=f_ext_rand_array,
                                   packed_size=len(etm.bodies) * 6)

    def etm_inverse_dynamics_packed(qdd_array=None,
                                    f_ext_array=None,
                                    grav_accn=None):
        return pack_array(array=etm.inverse_dynamics(qdd_array=qdd_array,
                                                     f_ext_array=f_ext_array,
                                                     grav_accn=grav_accn),
                          packed_size=etm.degrees_of_freedom)

    def etm_forward_dynamics_ab_packed(tau_array=None,
                                       f_ext_array=None,
                                       grav_accn=None):
        return pack_array(array=etm.forward_dynamics_ab(
            tau_array=tau_array, f_ext_array=f_ext_array, grav_accn=grav_accn),
                          packed_size=etm.degrees_of_freedom)

    #
    e = etm_inverse_dynamics_packed(qdd_array=qdd_rand_array)
    f = ftm.inverse_dynamics_packed(qdd_packed=qdd_rand_packed)
    assert approx_equal(e, f)
    e = etm_inverse_dynamics_packed(f_ext_array=f_ext_rand_array)
    f = ftm.inverse_dynamics_packed(f_ext_packed=f_ext_rand_packed)
    assert approx_equal(e, f)
    e = etm_inverse_dynamics_packed(grav_accn=grav_accn_rand)
    f = ftm.inverse_dynamics_packed(grav_accn=flex.double(grav_accn_rand))
    assert approx_equal(e, f)
    for qdd_array, qdd_packed in [(None, None),
                                  (qdd_rand_array, qdd_rand_packed)]:
        for f_ext_array, f_ext_packed in [(None, None),
                                          (f_ext_rand_array, f_ext_rand_packed)
                                          ]:
            for grav_accn in [None, grav_accn_rand]:
                if ([qdd_array, f_ext_array, grav_accn].count(None) >= 2):
                    continue  # exercised above already
                e = etm_inverse_dynamics_packed(qdd_array=qdd_rand_array,
                                                f_ext_array=f_ext_rand_array,
                                                grav_accn=grav_accn_rand)
                f = ftm.inverse_dynamics_packed(
                    qdd_packed=qdd_rand_packed,
                    f_ext_packed=f_ext_rand_packed,
                    grav_accn=flex.double(grav_accn_rand))
                assert approx_equal(e, f)
    #
    e = etm_forward_dynamics_ab_packed()
    f = ftm.forward_dynamics_ab_packed()
    assert approx_equal(e, f)
    e = etm_forward_dynamics_ab_packed(tau_array=tau_rand_array)
    f = ftm.forward_dynamics_ab_packed(tau_packed=tau_rand_packed)
    assert approx_equal(e, f)
    e = etm_forward_dynamics_ab_packed(f_ext_array=f_ext_rand_array)
    f = ftm.forward_dynamics_ab_packed(f_ext_packed=f_ext_rand_packed)
    assert approx_equal(e, f)
    e = etm_forward_dynamics_ab_packed(grav_accn=grav_accn_rand)
    f = ftm.forward_dynamics_ab_packed(grav_accn=flex.double(grav_accn_rand))
    assert approx_equal(e, f)
    for tau_array, tau_packed in [(None, None),
                                  (tau_rand_array, tau_rand_packed)]:
        for f_ext_array, f_ext_packed in [(None, None),
                                          (f_ext_rand_array, f_ext_rand_packed)
                                          ]:
            for grav_accn in [None, grav_accn_rand]:
                if (grav_accn is None):
                    grav_accn_f = None
                else:
                    grav_accn_f = flex.double(grav_accn)
                qdd_array_e = etm.forward_dynamics_ab(tau_array=tau_array,
                                                      f_ext_array=f_ext_array,
                                                      grav_accn=grav_accn)
                qdd_packed_e = pack_array(array=qdd_array_e,
                                          packed_size=etm.degrees_of_freedom)
                qdd_packed_f = ftm.forward_dynamics_ab_packed(
                    tau_packed=tau_packed,
                    f_ext_packed=f_ext_packed,
                    grav_accn=grav_accn_f)
                assert approx_equal(qdd_packed_e, qdd_packed_f)
                tau2_array_e = etm.inverse_dynamics(qdd_array=qdd_array_e,
                                                    f_ext_array=f_ext_array,
                                                    grav_accn=grav_accn)
                tau2_packed_e = pack_array(array=tau2_array_e,
                                           packed_size=etm.degrees_of_freedom)
                tau2_packed_f = ftm.inverse_dynamics_packed(
                    qdd_packed=qdd_packed_f,
                    f_ext_packed=f_ext_packed,
                    grav_accn=grav_accn_f)
                assert approx_equal(tau2_packed_e, tau2_packed_f)
                if (etm.degrees_of_freedom == 0):
                    assert tau2_packed_e.size() == 0
                elif (not have_singularity):
                    if (tau_packed is None):
                        assert is_below_limit(flex.max(
                            flex.abs(tau2_packed_e)),
                                              0,
                                              eps=1e-5)
                    else:
                        assert approx_equal(tau2_packed_e,
                                            tau_packed,
                                            eps=1e-5)
                qdd2_array_e = etm.forward_dynamics_ab(tau_array=tau2_array_e,
                                                       f_ext_array=f_ext_array,
                                                       grav_accn=grav_accn)
                qdd2_packed_e = pack_array(array=qdd2_array_e,
                                           packed_size=etm.degrees_of_freedom)
                qdd2_packed_f = ftm.forward_dynamics_ab_packed(
                    tau_packed=tau2_packed_f,
                    f_ext_packed=f_ext_packed,
                    grav_accn=grav_accn_f)
                assert approx_equal(qdd2_packed_e, qdd2_packed_f)
                assert approx_equal(qdd2_packed_e, qdd_packed_e, eps=1e-4)
    #
    def check_qdd():
        e = pack_array(array=etm.qdd_array(),
                       packed_size=etm.degrees_of_freedom)
        f = ftm.qdd_packed()
        assert approx_equal(e, f)

    check_qdd()
    ftm.flag_positions_as_changed()
    assert not ftm.sites_moved_is_cached()
    assert not ftm.qdd_array_is_cached()
    ftm.sites_moved()
    assert ftm.sites_moved_is_cached()
    assert not ftm.qdd_array_is_cached()
    check_qdd()
    assert ftm.sites_moved_is_cached()
    assert ftm.qdd_array_is_cached()
    ftm.unpack_q(q_packed=ftm.pack_q())
    assert not ftm.sites_moved_is_cached()
    assert not ftm.qdd_array_is_cached()
    ftm.qdd_packed()
    if (ftm.potential_obj is None):
        assert not ftm.sites_moved_is_cached()
        ftm.sites_moved()
    assert ftm.sites_moved_is_cached()
    assert ftm.qdd_array_is_cached()
    ftm.unpack_qd(qd_packed=ftm.pack_qd())
    assert ftm.sites_moved_is_cached()
    assert not ftm.qdd_array_is_cached()
    check_qdd()
    #
    delta_t = 0.1234
    etm.dynamics_step(delta_t=delta_t)
    ftm.dynamics_step(delta_t=delta_t)
    assert not ftm.sites_moved_is_cached()
    assert not ftm.qdd_array_is_cached()
    check_packed()
    check_qdd()
    #
    etm.assign_zero_velocities()
    ftm.assign_zero_velocities()
    e = etm_inverse_dynamics_packed(f_ext_array=f_ext_rand_array)
    f = ftm.inverse_dynamics_packed(f_ext_packed=f_ext_rand_packed)
    assert approx_equal(e, f)
    e_ref = e
    e = pack_array(array=etm.f_ext_as_tau(f_ext_array=f_ext_array),
                   packed_size=etm.degrees_of_freedom)
    assert approx_equal(e_ref, e)
    f = ftm.f_ext_as_tau_packed(f_ext_packed=f_ext_packed)
    assert approx_equal(e_ref, f)
    #
    if (run_minimization):
        check_packed()
        etm.minimization(max_iterations=3)
        ftm.minimization(max_iterations=3)
        check_packed()