# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2018.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Pass manager for optimization level 2, providing medium optimization.
Level 2 pass manager: medium optimization by noise adaptive qubit mapping and
gate cancellation using commutativity rules.
"""
from __future__ import annotations
from qiskit.transpiler.basepasses import BasePass
from qiskit.transpiler.passmanager_config import PassManagerConfig
from qiskit.transpiler.timing_constraints import TimingConstraints
from qiskit.transpiler.passmanager import PassManager
from qiskit.transpiler.passmanager import StagedPassManager
from qiskit.transpiler import ConditionalController, FlowController
from qiskit.transpiler.passes import SetLayout
from qiskit.transpiler.passes import VF2Layout
from qiskit.transpiler.passes import TrivialLayout
from qiskit.transpiler.passes import DenseLayout
from qiskit.transpiler.passes import NoiseAdaptiveLayout
from qiskit.transpiler.passes import SabreLayout
from qiskit.transpiler.passes import FixedPoint
from qiskit.transpiler.passes import Depth
from qiskit.transpiler.passes import Size
from qiskit.transpiler.passes import Optimize1qGatesDecomposition
from qiskit.transpiler.passes import CommutativeCancellation
from qiskit.transpiler.passes import GatesInBasis
from qiskit.transpiler.passes import BarrierBeforeFinalMeasurements
from qiskit.transpiler.preset_passmanagers import common
from qiskit.transpiler.passes.layout.vf2_layout import VF2LayoutStopReason
from qiskit.transpiler.preset_passmanagers.plugin import (
PassManagerStagePluginManager,
)
[docs]def level_2_pass_manager(pass_manager_config: PassManagerConfig) -> StagedPassManager:
"""Level 2 pass manager: medium optimization by initial layout selection and
gate cancellation using commutativity rules.
This pass manager applies the user-given initial layout. If none is given, a search
for a perfect layout (i.e. one that satisfies all 2-qubit interactions) is conducted.
If no such layout is found, qubits are laid out on the most densely connected subset
which also exhibits the best gate fidelities.
The pass manager then transforms the circuit to match the coupling constraints.
It is then unrolled to the basis, and any flipped cx directions are fixed.
Finally, optimizations in the form of commutative gate cancellation and redundant
reset removal are performed.
Args:
pass_manager_config: configuration of the pass manager.
Returns:
a level 2 pass manager.
Raises:
TranspilerError: if the passmanager config is invalid.
"""
plugin_manager = PassManagerStagePluginManager()
basis_gates = pass_manager_config.basis_gates
inst_map = pass_manager_config.inst_map
coupling_map = pass_manager_config.coupling_map
initial_layout = pass_manager_config.initial_layout
init_method = pass_manager_config.init_method
layout_method = pass_manager_config.layout_method or "sabre"
routing_method = pass_manager_config.routing_method or "sabre"
translation_method = pass_manager_config.translation_method or "translator"
optimization_method = pass_manager_config.optimization_method
scheduling_method = pass_manager_config.scheduling_method
instruction_durations = pass_manager_config.instruction_durations
seed_transpiler = pass_manager_config.seed_transpiler
backend_properties = pass_manager_config.backend_properties
approximation_degree = pass_manager_config.approximation_degree
unitary_synthesis_method = pass_manager_config.unitary_synthesis_method
timing_constraints = pass_manager_config.timing_constraints or TimingConstraints()
unitary_synthesis_plugin_config = pass_manager_config.unitary_synthesis_plugin_config
target = pass_manager_config.target
hls_config = pass_manager_config.hls_config
# Search for a perfect layout, or choose a dense layout, if no layout given
_given_layout = SetLayout(initial_layout)
def _choose_layout_condition(property_set):
# layout hasn't been set yet
return not property_set["layout"]
def _vf2_match_not_found(property_set):
# If a layout hasn't been set by the time we run vf2 layout we need to
# run layout
if property_set["layout"] is None:
return True
# if VF2 layout stopped for any reason other than solution found we need
# to run layout since VF2 didn't converge.
if (
property_set["VF2Layout_stop_reason"] is not None
and property_set["VF2Layout_stop_reason"] is not VF2LayoutStopReason.SOLUTION_FOUND
):
return True
return False
# Try using VF2 layout to find a perfect layout
_choose_layout_0: list[BasePass] | BasePass = (
[]
if pass_manager_config.layout_method
else VF2Layout(
coupling_map,
seed=seed_transpiler,
call_limit=int(5e6), # Set call limit to ~10 sec with rustworkx 0.10.2
properties=backend_properties,
target=target,
max_trials=25000, # Limits layout scoring to < 6 sec on ~400 qubit devices
)
)
if target is None:
coupling_map_layout = coupling_map
else:
coupling_map_layout = target
if layout_method == "trivial":
_choose_layout_1: BasePass = TrivialLayout(coupling_map_layout)
elif layout_method == "dense":
_choose_layout_1 = DenseLayout(coupling_map, backend_properties, target=target)
elif layout_method == "noise_adaptive":
if target is None:
_choose_layout_1 = NoiseAdaptiveLayout(backend_properties)
else:
_choose_layout_1 = NoiseAdaptiveLayout(target)
elif layout_method == "sabre":
_choose_layout_1 = SabreLayout(
coupling_map_layout,
max_iterations=2,
seed=seed_transpiler,
swap_trials=10,
layout_trials=10,
skip_routing=pass_manager_config.routing_method is not None
and routing_method != "sabre",
)
# Choose routing pass
routing_pm = plugin_manager.get_passmanager_stage(
"routing", routing_method, pass_manager_config, optimization_level=2
)
# Build optimization loop: 1q rotation merge and commutative cancellation iteratively until
# no more change in depth
_depth_check = [Depth(recurse=True), FixedPoint("depth")]
_size_check = [Size(recurse=True), FixedPoint("size")]
def _opt_control(property_set):
return (not property_set["depth_fixed_point"]) or (not property_set["size_fixed_point"])
_opt: list[BasePass] = [
Optimize1qGatesDecomposition(basis=basis_gates, target=target),
CommutativeCancellation(basis_gates=basis_gates, target=target),
]
unroll_3q = None
# Build pass manager
if coupling_map or initial_layout:
unroll_3q = common.generate_unroll_3q(
target,
basis_gates,
approximation_degree,
unitary_synthesis_method,
unitary_synthesis_plugin_config,
hls_config,
)
if layout_method not in {"trivial", "dense", "noise_adaptive", "sabre"}:
layout = plugin_manager.get_passmanager_stage(
"layout", layout_method, pass_manager_config, optimization_level=2
)
else:
def _swap_mapped(property_set):
return property_set["final_layout"] is None
layout = PassManager()
layout.append(_given_layout)
layout.append(_choose_layout_0, condition=_choose_layout_condition)
layout.append(
[BarrierBeforeFinalMeasurements(), _choose_layout_1], condition=_vf2_match_not_found
)
embed = common.generate_embed_passmanager(coupling_map_layout)
layout.append(
[pass_ for x in embed.passes() for pass_ in x["passes"]], condition=_swap_mapped
)
routing = routing_pm
else:
layout = None
routing = None
if translation_method not in {"translator", "synthesis", "unroller"}:
translation = plugin_manager.get_passmanager_stage(
"translation", translation_method, pass_manager_config, optimization_level=2
)
else:
translation = common.generate_translation_passmanager(
target,
basis_gates,
translation_method,
approximation_degree,
coupling_map,
backend_properties,
unitary_synthesis_method,
unitary_synthesis_plugin_config,
hls_config,
)
if (coupling_map and not coupling_map.is_symmetric) or (
target is not None and target.get_non_global_operation_names(strict_direction=True)
):
pre_optimization = common.generate_pre_op_passmanager(target, coupling_map, True)
else:
pre_optimization = common.generate_pre_op_passmanager(remove_reset_in_zero=True)
if optimization_method is None:
optimization = PassManager()
unroll = [pass_ for x in translation.passes() for pass_ in x["passes"]]
# Build nested Flow controllers
def _unroll_condition(property_set):
return not property_set["all_gates_in_basis"]
# Check if any gate is not in the basis, and if so, run unroll passes
_unroll_if_out_of_basis: list[BasePass | FlowController] = [
GatesInBasis(basis_gates, target=target),
ConditionalController(unroll, condition=_unroll_condition),
]
optimization.append(_depth_check + _size_check)
opt_loop = _opt + _unroll_if_out_of_basis + _depth_check + _size_check
optimization.append(opt_loop, do_while=_opt_control)
else:
optimization = plugin_manager.get_passmanager_stage(
"optimization", optimization_method, pass_manager_config, optimization_level=2
)
if scheduling_method is None or scheduling_method in {"alap", "asap"}:
sched = common.generate_scheduling(
instruction_durations,
scheduling_method,
timing_constraints,
inst_map,
target=target,
)
else:
sched = plugin_manager.get_passmanager_stage(
"scheduling", scheduling_method, pass_manager_config, optimization_level=2
)
init = common.generate_control_flow_options_check(
layout_method=layout_method,
routing_method=routing_method,
translation_method=translation_method,
optimization_method=optimization_method,
scheduling_method=scheduling_method,
basis_gates=basis_gates,
target=target,
)
if init_method is not None:
init += plugin_manager.get_passmanager_stage(
"init", init_method, pass_manager_config, optimization_level=2
)
elif unroll_3q is not None:
init += unroll_3q
return StagedPassManager(
init=init,
layout=layout,
routing=routing,
translation=translation,
pre_optimization=pre_optimization,
optimization=optimization,
scheduling=sched,
)