def apply_next_swaps(self, require_frontier_adjacency: bool = False):
"""Applies a few SWAPs to get the mapping closer to one in which the
next logical gates can be applied.
See route_circuit_greedily for more details.
"""
time_slices = get_time_slices(self.remaining_dag)
if require_frontier_adjacency:
frontier_edges = sorted(time_slices[0].edges)
self.bring_farthest_pair_together(frontier_edges)
return
for k in range(1, self.max_search_radius + 1):
candidate_swap_sets = list(self.get_edge_sets(k))
for time_slice in time_slices:
edges = sorted(time_slice.edges)
distance_vectors = list(
self.get_distance_vector(edges, swap_set)
for swap_set in candidate_swap_sets)
dominated_indices = _get_dominated_indices(distance_vectors)
candidate_swap_sets = [
S for i, S in enumerate(candidate_swap_sets)
if i not in dominated_indices
]
if len(candidate_swap_sets) == 1:
self.apply_swap(*candidate_swap_sets[0])
return
self.apply_next_swaps(True)
def set_initial_mapping(self,
initial_mapping: Optional[Dict[ops.Qid,
ops.Qid]] = None):
"""Sets the internal state according to an initial mapping.
Args:
initial_mapping: The mapping to use. If not given, one is found
greedily.
"""
if initial_mapping is None:
time_slices = get_time_slices(self.remaining_dag)
if not time_slices:
initial_mapping = dict(
zip(self.device_graph, self.logical_qubits))
else:
logical_graph = time_slices[0]
logical_graph.add_nodes_from(self.logical_qubits)
initial_mapping = get_initial_mapping(logical_graph,
self.device_graph,
self.prng)
self.initial_mapping = initial_mapping
self._phys_to_log = {
q: initial_mapping.get(q)
for q in self.physical_qubits
}
self._log_to_phys = {
l: p
for p, l in self._phys_to_log.items() if l is not None
}
self._assert_mapping_consistency()
