Struct LayoutObjective 

pub struct LayoutObjective {
    pub distance_weight: f64,
    pub direction_weight: f64,
    pub two_qubit_error_weight: f64,
    pub readout_error_weight: f64,
}

Weighted scoring objective used to rank candidate layouts.

All weights must be finite and non-negative. Setting a weight to 0.0 removes that component from the total score. The raw components are still reported in LayoutScore when they can be computed.

Fields

distance_weight: f64

Weight for weighted logical interaction distance.

Each interaction contributes interaction.weight * physical_distance.

direction_weight: f64

Weight for directly adjacent interactions whose observed operation direction is unsupported by the directed coupling graph.

two_qubit_error_weight: f64

Weight for effective two-qubit fidelity cost.

Known gate-specific calibrations contribute their error probability. A gate that is native elsewhere on the device but unsupported or uncalibrated on the candidate edge contributes the conservative upper bound 1.0. This is a placement-ranking penalty, not a measured error rate or circuit-success estimate.

readout_error_weight: f64

Weight for known readout error rates.

Readout error is scaled by logical activity. Interaction-free circuits assign activity 1.0 to each logical qubit so idle layouts can still be ranked by readout fidelity.

Implementations

impl LayoutObjective

pub fn topology_only() -> Self

Creates a topology-only objective.

This ranks by interaction distance and directed-coupling mismatch only, ignoring all calibration data even if the target device provides it.

pub fn auto_from_physical(physical: &PhysicalLayoutGraph) -> Self

Creates a fidelity-aware objective when useful calibration data exists.

If the physical graph has no usable error-rate data, this falls back to LayoutObjective::topology_only instead of failing.

pub fn fidelity_required( physical: &PhysicalLayoutGraph, ) -> Result<Self, CompilerError>

Creates a fidelity-aware objective and requires calibration data.

Use this for workflows where silently falling back to topology-only scoring would hide a device-data configuration problem.

pub fn fidelity_aware() -> Self

Creates the default fidelity-aware objective.

The default weights keep topology distance and direction mismatch active while making known two-qubit error rates a stronger tie-breaker than readout error.

pub fn uses_fidelity(&self) -> bool

Returns whether any fidelity/error term can affect scoring.

pub fn score_layout( &self, analysis: &CircuitLayoutAnalysis, physical: &PhysicalLayoutGraph, layout: &Layout, ) -> Result<LayoutScore, CompilerError>

Scores a candidate layout against circuit and physical-graph analysis.

The layout must map every logical qubit in analysis. Interactions whose mapped physical qubits are disconnected are rejected because the resulting mapping cannot be routed within the usable topology.

Errors

Returns CompilerError::InvalidInput for invalid objective weights or disconnected mapped interactions. Returns CompilerError::InvariantViolation if the layout omits a logical qubit present in the analysis.

Trait Implementations

impl Clone for LayoutObjective

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LayoutObjective

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for LayoutObjective

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for LayoutObjective

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for LayoutObjective