Function greedy_layout 

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

Builds a deterministic greedy initial layout from weighted interactions.

The algorithm places higher-weight logical interactions first. For each interaction it chooses the closest currently feasible physical placement, using the shared LayoutObjective as a local tie-breaker for direction and calibration data. Routing remains a later pass: this function only selects an initial logical-to-physical mapping.

This is a good default candidate generator for larger devices where VF2 may be too expensive or where a perfect topology embedding does not exist.

Errors

Returns CompilerError::InvalidInput if there are fewer usable physical qubits than logical qubits, no physical candidate can be selected for a required placement, or if final objective scoring rejects the layout.

Examples

use cqlib_core::circuit::{Circuit, Qubit};
use cqlib_core::compile::transform::{LayoutObjective, greedy_layout};
use cqlib_core::device::{Device, LogicalQubit, PhysicalQubit};

let device = Device::line("line-3", 3).unwrap();
let objective = LayoutObjective::topology_only();

let mut circuit = Circuit::new(3);
circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
circuit.cx(Qubit::new(1), Qubit::new(2)).unwrap();

let result = greedy_layout(&circuit, &device, &objective).unwrap();
assert_eq!(
    result.layout.get_physical(LogicalQubit::new(0)),
    Some(PhysicalQubit::new(0)),
);
assert!(result.diagnostics.is_perfect);