level3.py

# 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 3, providing heavy optimization.

Level 3 pass manager: heavy optimization by noise adaptive qubit mapping and
gate cancellation using commutativity rules and unitary synthesis.
"""


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.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 RemoveResetInZeroState
from qiskit.transpiler.passes import Optimize1qGatesDecomposition
from qiskit.transpiler.passes import CommutativeCancellation
from qiskit.transpiler.passes import OptimizeSwapBeforeMeasure
from qiskit.transpiler.passes import RemoveDiagonalGatesBeforeMeasure
from qiskit.transpiler.passes import Collect2qBlocks
from qiskit.transpiler.passes import ConsolidateBlocks
from qiskit.transpiler.passes import UnitarySynthesis
from qiskit.transpiler.passes import GatesInBasis
from qiskit.transpiler.passes import BarrierBeforeFinalMeasurements
from qiskit.transpiler.runningpassmanager import ConditionalController
from qiskit.transpiler.preset_passmanagers import common
from qiskit.transpiler.passes.layout.vf2_layout import VF2LayoutStopReason
from qiskit.transpiler.preset_passmanagers.plugin import (
    PassManagerStagePluginManager,
)


def level_3_pass_manager(pass_manager_config: PassManagerConfig) -> StagedPassManager:
    """Level 3 pass manager: heavy optimization by noise adaptive qubit mapping and
    gate cancellation using commutativity rules and unitary synthesis.

    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, and device calibration information is available, the
    circuit is mapped to the qubits with best readouts and to CX gates with highest fidelity.

    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, resynthesis
    of two-qubit unitary blocks, and redundant reset removal are performed.

    Args:
        pass_manager_config: configuration of the pass manager.

    Returns:
        a level 3 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

    # Layout on good qubits if calibration info available, otherwise on dense links
    _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

    # 2a. If layout method is not set, first try VF2Layout
    _choose_layout_0 = (
        []
        if pass_manager_config.layout_method
        else VF2Layout(
            coupling_map,
            seed=seed_transpiler,
            call_limit=int(3e7),  # Set call limit to ~60 sec with rustworkx 0.10.2
            properties=backend_properties,
            target=target,
        )
    )
    # 2b. if VF2 didn't converge on a solution use layout_method (dense).
    if layout_method == "trivial":
        _choose_layout_1 = TrivialLayout(coupling_map)
    elif layout_method == "dense":
        _choose_layout_1 = DenseLayout(coupling_map, backend_properties, target=target)
    elif layout_method == "noise_adaptive":
        _choose_layout_1 = NoiseAdaptiveLayout(backend_properties)
    elif layout_method == "sabre":
        _choose_layout_1 = SabreLayout(
            coupling_map,
            max_iterations=4,
            seed=seed_transpiler,
            swap_trials=20,
            layout_trials=20,
            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=3
    )

    # 8. Optimize iteratively until no more change in depth. Removes useless gates
    # after reset and before measure, commutes gates and optimizes contiguous blocks.
    _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 = [
        Collect2qBlocks(),
        ConsolidateBlocks(basis_gates=basis_gates, target=target),
        UnitarySynthesis(
            basis_gates,
            approximation_degree=approximation_degree,
            coupling_map=coupling_map,
            backend_props=backend_properties,
            method=unitary_synthesis_method,
            plugin_config=unitary_synthesis_plugin_config,
            target=target,
        ),
        Optimize1qGatesDecomposition(basis=basis_gates, target=target),
        CommutativeCancellation(target=target),
    ]

    # Build pass manager
    init = common.generate_error_on_control_flow(
        "The optimizations in optimization_level=3 do not yet support control flow."
    )
    if init_method is not None:
        init += plugin_manager.get_passmanager_stage(
            "init", init_method, pass_manager_config, optimization_level=2
        )
    else:
        init += common.generate_unroll_3q(
            target,
            basis_gates,
            approximation_degree,
            unitary_synthesis_method,
            unitary_synthesis_plugin_config,
            hls_config,
        )
    init.append(RemoveResetInZeroState())
    init.append(OptimizeSwapBeforeMeasure())
    init.append(RemoveDiagonalGatesBeforeMeasure())
    if coupling_map or initial_layout:
        if layout_method not in {"trivial", "dense", "noise_adaptive", "sabre"}:
            layout = plugin_manager.get_passmanager_stage(
                "layout", layout_method, pass_manager_config, optimization_level=3
            )
        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.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=3
        )
    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 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 = [
            GatesInBasis(basis_gates, target=target),
            ConditionalController(unroll, condition=_unroll_condition),
        ]

        optimization.append(_depth_check + _size_check)
        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)
            _direction = [
                pass_
                for x in common.generate_pre_op_passmanager(target, coupling_map).passes()
                for pass_ in x["passes"]
            ]
            # For transpiling to a target we need to run GateDirection in the
            # optimization loop to correct for incorrect directions that might be
            # inserted by UnitarySynthesis which is direction aware but only via
            # the coupling map which with a target doesn't give a full picture
            if target is not None and optimization is not None:
                optimization.append(
                    _opt + _unroll_if_out_of_basis + _depth_check + _size_check + _direction,
                    do_while=_opt_control,
                )
            elif optimization is not None:
                optimization.append(
                    _opt + _unroll_if_out_of_basis + _depth_check + _size_check,
                    do_while=_opt_control,
                )
        else:
            pre_optimization = common.generate_pre_op_passmanager(remove_reset_in_zero=True)
            optimization.append(
                _opt + _unroll_if_out_of_basis + _depth_check + _size_check, do_while=_opt_control
            )
    else:
        optimization = plugin_manager.get_passmanager_stage(
            "optimization", optimization_method, pass_manager_config, optimization_level=3
        )
        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 scheduling_method is None or scheduling_method in {"alap", "asap"}:
        sched = common.generate_scheduling(
            instruction_durations, scheduling_method, timing_constraints, inst_map, target=target
        )
    elif isinstance(scheduling_method, PassManager):
        sched = scheduling_method
    else:
        sched = plugin_manager.get_passmanager_stage(
            "scheduling", scheduling_method, pass_manager_config, optimization_level=3
        )

    return StagedPassManager(
        init=init,
        layout=layout,
        routing=routing,
        translation=translation,
        pre_optimization=pre_optimization,
        optimization=optimization,
        scheduling=sched,
    )