def step_c1(self, state, dt):
pos_init = state.pos.copy()
state.pos += dt * self.system.dh_dmom(state)
pos_fwd = state.pos.copy()
self.step_c2(state, -dt)
rev_diff = self.reverse_check_norm(state.pos - pos_init)
if rev_diff > self.reverse_check_tol:
raise NonReversibleStepError(
f'Non-reversible step. Distance between initial and '
f'forward-backward integrated positions = {rev_diff:.1e}.')
state.pos = pos_fwd
def step_b2(self, state, dt):
mom_init = state.mom.copy()
state.mom -= dt * self.system.dh2_dpos(state)
mom_fwd = state.mom.copy()
self.step_b1(state, -dt)
rev_diff = self.reverse_check_norm(state.mom - mom_init)
if rev_diff > self.reverse_check_tol:
raise NonReversibleStepError(
f'Non-reversible step. Distance between initial and '
f'forward-backward integrated momentums = {rev_diff:.1e}.')
state.mom = mom_fwd
def step_b(self, state, dt):
dt_i = dt / self.n_inner_step
for i in range(self.n_inner_step):
state_prev = state.copy()
self.step_b_inner(state, dt_i)
self.project_onto_manifold(state, state_prev)
self.solve_for_mom_post_projection(state, state_prev, dt_i)
self.project_onto_cotangent_space(state)
state_back = state.copy()
self.step_b_inner(state_back, -dt_i)
self.project_onto_manifold(state_back, state)
rev_diff = self.reverse_check_norm(state_back.pos - state_prev.pos)
if rev_diff > self.reverse_check_tol:
raise NonReversibleStepError(
f'Non-reversible step. Distance between initial and '
f'forward-backward integrated positions = {rev_diff:.1e}.')