def _layout_and_route_passmanager(self, initial_layout):
"""Return a passmanager for a full layout and routing.
We use a factory to remove potential statefulness of passes.
"""
layout_and_route = [SetLayout(initial_layout),
FullAncillaAllocation(self.coupling_map),
EnlargeWithAncilla(),
ApplyLayout(),
self.routing_pass]
pm = PassManager(layout_and_route)
return pm
def __init__(
self,
coupling_map,
objective="depth",
backend_prop=None,
time_limit=30,
threads=None,
max_swaps_inbetween_layers=None,
):
"""BIPMapping initializer.
Args:
coupling_map (CouplingMap): Directed graph represented a coupling map.
objective (str): Type of objective function:
* ``'error_rate'``: [NotImplemented] Predicted error rate of the circuit
* ``'depth'``: [Default] Depth (number of time-steps) of the circuit
* ``'balanced'``: [NotImplemented] Weighted sum of ``'error_rate'`` and ``'depth'``
backend_prop (BackendProperties): Backend properties object
time_limit (float): Time limit for solving BIP in seconds
threads (int): Number of threads to be allowed for CPLEX to solve BIP
max_swaps_inbetween_layers (int):
Number of swaps allowed in between layers. If None, automatically set.
Large value could decrease the probability to build infeasible BIP problem but also
could reduce the chance of finding a feasible solution within the ``time_limit``.
Raises:
MissingOptionalLibraryError: if cplex or docplex are not installed.
"""
if not HAS_DOCPLEX or not HAS_CPLEX:
raise MissingOptionalLibraryError(
libname="bip-mapper",
name="BIP-based mapping pass",
pip_install="pip install 'qiskit-terra[bip-mapper]'",
)
super().__init__()
self.coupling_map = copy.deepcopy(
coupling_map) # save a copy to modify
if self.coupling_map is not None:
self.coupling_map.make_symmetric()
self.objective = objective
self.backend_prop = backend_prop
self.time_limit = time_limit
self.threads = threads
self.max_swaps_inbetween_layers = max_swaps_inbetween_layers
# ensure the number of virtual and physical qubits are the same
self.requires.append(TrivialLayout(self.coupling_map))
self.requires.append(FullAncillaAllocation(self.coupling_map))
self.requires.append(EnlargeWithAncilla())