Function sabre_layout 

pub fn sabre_layout(
    circuit: &Circuit,
    device: &Device,
    objective: &LayoutObjective,
    config: &SabreConfig,
) -> Result<LayoutResult, CompilerError>

Selects an initial layout with fused SABRE refinement and routing search.

The search completes every configured refinement iteration before routing the resulting layout. Complete routes are never created for intermediate refinement states. This layout-only API returns the winning route’s initial layout; crate::compile::transform::route_sabre consumes the same fused result directly and does not route the winner a second time.

Candidate layouts include deterministic component-feasible anchors, reachable greedy/VF2 and interaction-aware layouts, plus the full randomized budget controlled by SabreConfig::layout_trials. Each candidate is refined through SABRE forward/backward passes; complete trials are ranked by predicted native two-qubit count, native two-qubit depth, native total depth, and stable candidate/trial order. LayoutObjective contributes candidate generation and diagnostics, but is not the final selection key.

Errors

Returns CompilerError::InvalidInput for invalid SABRE layout configuration, insufficient usable physical qubits, unreachable interactions in the usable topology, or unsupported circuit operations.

Examples

use cqlib_core::circuit::{Circuit, Qubit};
use cqlib_core::compile::sabre::SabreConfig;
use cqlib_core::compile::transform::{LayoutObjective, sabre_layout};
use cqlib_core::device::Device;

let mut circuit = Circuit::new(3);
circuit.cx(Qubit::new(0), Qubit::new(2)).unwrap();
let device = Device::line("line-3", 3).unwrap();

let result = sabre_layout(
    &circuit,
    &device,
    &LayoutObjective::topology_only(),
    &SabreConfig::default(),
)
.unwrap();
assert!(result.score.is_some());