def run(self, dag):
"""Run one pass of the lookahead mapper on the provided DAG.
Args:
dag (DAGCircuit): the directed acyclic graph to be mapped
Returns:
DAGCircuit: A dag mapped to be compatible with the coupling_map in
the property_set.
Raises:
MapperError: If the provided DAG has more qubits than are available
in the coupling map.
"""
# Preserve fix for https://github.com/Qiskit/qiskit-terra/issues/674
removed_measures = remove_last_measurements(dag)
coupling_map = self._coupling_map
ordered_virtual_gates = list(dag.serial_layers())
if len(dag.get_qubits()) > len(coupling_map.physical_qubits):
raise MapperError(
'DAG contains more qubits than are present in the coupling map.'
)
dag_qubits = dag.get_qubits()
coupling_qubits = coupling_map.physical_qubits
starting_layout = [
dag_qubits[i] if i < len(dag_qubits) else None
for i in range(len(coupling_qubits))
]
mapped_gates = []
layout = Layout(starting_layout)
gates_remaining = ordered_virtual_gates.copy()
while gates_remaining:
best_step = _search_forward_n_swaps(layout, gates_remaining,
coupling_map)
layout = best_step['layout']
gates_mapped = best_step['gates_mapped']
gates_remaining = best_step['gates_remaining']
mapped_gates.extend(gates_mapped)
# Preserve input DAG's name, regs, wire_map, etc. but replace the graph.
mapped_dag = _copy_circuit_metadata(dag, coupling_map)
for gate in mapped_gates:
mapped_dag.apply_operation_back(**gate)
return_last_measurements(mapped_dag, removed_measures, layout)
return mapped_dag
def transpile(dag,
basis_gates='u1,u2,u3,cx,id',
coupling_map=None,
initial_layout=None,
get_layout=False,
format='dag',
seed=None,
pass_manager=None):
"""Transform a dag circuit into another dag circuit (transpile), through
consecutive passes on the dag.
Args:
dag (DAGCircuit): dag circuit to transform via transpilation
basis_gates (str): a comma separated string for the target basis gates
coupling_map (list): A graph of coupling::
[
[control0(int), target0(int)],
[control1(int), target1(int)],
]
eg. [[0, 2], [1, 2], [1, 3], [3, 4]}
initial_layout (dict): A mapping of qubit to qubit::
{
("q", start(int)): ("q", final(int)),
...
}
eg.
{
("q", 0): ("q", 0),
("q", 1): ("q", 1),
("q", 2): ("q", 2),
("q", 3): ("q", 3)
}
get_layout (bool): flag for returning the final layout after mapping
format (str): The target format of the compilation:
{'dag', 'json', 'qasm'}
seed (int): random seed for the swap mapper
pass_manager (PassManager): pass manager instance for the transpilation process
If None, a default set of passes are run.
Otherwise, the passes defined in it will run.
If contains no passes in it, no dag transformations occur.
Returns:
DAGCircuit: transformed dag
DAGCircuit, dict: transformed dag along with the final layout on backend qubits
Raises:
TranspilerError: if the format is not valid.
"""
# TODO: `basis_gates` will be removed after we have the unroller pass.
# TODO: `coupling_map`, `initial_layout`, `get_layout`, `seed` removed after mapper pass.
# TODO: move this to the mapper pass
num_qubits = sum(dag.qregs.values())
if num_qubits == 1 or coupling_map == "all-to-all":
coupling_map = None
final_layout = None
if pass_manager:
# run the passes specified by the pass manager
# TODO return the property set too. See #1086
dag = pass_manager.run_passes(dag)
else:
# default set of passes
# TODO: move each step here to a pass, and use a default passmanager below
basis = basis_gates.split(',') if basis_gates else []
dag_unroller = DagUnroller(dag, DAGBackend(basis))
dag = dag_unroller.expand_gates()
# if a coupling map is given compile to the map
if coupling_map:
logger.info("pre-mapping properties: %s", dag.property_summary())
# Insert swap gates
coupling = Coupling(coupling_list2dict(coupling_map))
removed_meas = remove_last_measurements(dag)
logger.info("measurements moved: %s", removed_meas)
logger.info("initial layout: %s", initial_layout)
dag, final_layout, last_layout = swap_mapper(dag,
coupling,
initial_layout,
trials=20,
seed=seed)
logger.info("final layout: %s", final_layout)
# Expand swaps
dag_unroller = DagUnroller(dag, DAGBackend(basis))
dag = dag_unroller.expand_gates()
# Change cx directions
dag = direction_mapper(dag, coupling)
# Simplify cx gates
cx_cancellation(dag)
# Simplify single qubit gates
dag = optimize_1q_gates(dag)
return_last_measurements(dag, removed_meas, last_layout)
logger.info("post-mapping properties: %s", dag.property_summary())
# choose output format
# TODO: do we need all of these formats, or just the dag?
if format == 'dag':
compiled_circuit = dag
elif format == 'json':
# FIXME: JsonBackend is wrongly taking an ordered dict as basis, not list
dag_unroller = DagUnroller(dag, JsonBackend(dag.basis))
compiled_circuit = dag_unroller.execute()
elif format == 'qasm':
compiled_circuit = dag.qasm()
else:
raise TranspilerError('unrecognized circuit format')
if get_layout:
return compiled_circuit, final_layout
return compiled_circuit
def transpile_dag(dag,
basis_gates='u1,u2,u3,cx,id',
coupling_map=None,
initial_layout=None,
get_layout=False,
format='dag',
seed_mapper=None,
pass_manager=None):
"""Transform a dag circuit into another dag circuit (transpile), through
consecutive passes on the dag.
Args:
dag (DAGCircuit): dag circuit to transform via transpilation
basis_gates (str): a comma separated string for the target basis gates
coupling_map (list): A graph of coupling::
[
[control0(int), target0(int)],
[control1(int), target1(int)],
]
eg. [[0, 2], [1, 2], [1, 3], [3, 4]}
initial_layout (dict): A mapping of qubit to qubit::
{
("q", start(int)): ("q", final(int)),
...
}
eg.
{
("q", 0): ("q", 0),
("q", 1): ("q", 1),
("q", 2): ("q", 2),
("q", 3): ("q", 3)
}
get_layout (bool): flag for returning the final layout after mapping
format (str): DEPRECATED The target format of the compilation: {'dag', 'json', 'qasm'}
seed_mapper (int): random seed_mapper for the swap mapper
pass_manager (PassManager): pass manager instance for the transpilation process
If None, a default set of passes are run.
Otherwise, the passes defined in it will run.
If contains no passes in it, no dag transformations occur.
Returns:
DAGCircuit: transformed dag
DAGCircuit, dict: transformed dag along with the final layout on backend qubits
"""
# TODO: `basis_gates` will be removed after we have the unroller pass.
# TODO: `coupling_map`, `initial_layout`, `get_layout`, `seed_mapper` removed after mapper pass.
# TODO: move this to the mapper pass
num_qubits = sum([qreg.size for qreg in dag.qregs.values()])
if num_qubits == 1 or coupling_map == "all-to-all":
coupling_map = None
final_layout = None
if pass_manager:
# run the passes specified by the pass manager
# TODO return the property set too. See #1086
dag = pass_manager.run_passes(dag)
else:
# default set of passes
# TODO: move each step here to a pass, and use a default passmanager below
basis = basis_gates.split(',') if basis_gates else []
dag = Unroller(basis).run(dag)
# if a coupling map is given compile to the map
if coupling_map:
logger.info("pre-mapping properties: %s", dag.properties())
# Insert swap gates
coupling = Coupling(couplinglist=coupling_map)
removed_meas = remove_last_measurements(dag)
logger.info("measurements moved: %s", removed_meas)
logger.info("initial layout: %s", initial_layout)
dag, final_layout, last_layout = swap_mapper(dag,
coupling,
initial_layout,
trials=20,
seed=seed_mapper)
logger.info("final layout: %s", final_layout)
# Expand swaps
dag = Unroller(basis).run(dag)
# Change cx directions
dag = direction_mapper(dag, coupling)
# Simplify cx gates
cx_cancellation(dag)
# Simplify single qubit gates
dag = optimize_1q_gates(dag)
return_last_measurements(dag, removed_meas, last_layout)
logger.info("post-mapping properties: %s", dag.properties())
if format != 'dag':
warnings.warn(
"transpiler no longer supports different formats. "
"only dag to dag transformations are supported.",
DeprecationWarning)
if get_layout:
return dag, final_layout
return dag
