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Use rust-native error for DisjointLayout #16305

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32aae71
Use rust-native error for `DisjointLayout`
raynelfss May 28, 2026
3925e3d
Update crates/transpiler/src/passes/disjoint_layout.rs
raynelfss May 28, 2026
4af28c2
Update crates/transpiler/src/passes/disjoint_layout.rs
raynelfss May 29, 2026
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65 changes: 45 additions & 20 deletions crates/transpiler/src/passes/disjoint_layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ use pyo3::create_exception;
use pyo3::intern;
use pyo3::prelude::*;
use pyo3::types::PyList;
use qiskit_circuit::dag_circuit::DAGError;
use rustworkx_core::connectivity::connected_components;
use rustworkx_core::petgraph::EdgeType;
use rustworkx_core::petgraph::prelude::*;
Expand All @@ -37,6 +38,30 @@ use qiskit_util::py::ImportOnceCell;

create_exception!(qiskit, MultiQEncountered, pyo3::exceptions::PyException);

#[derive(Debug, thiserror::Error)]
pub enum DisjointLayoutError {
#[error("Encountered >2 qubit instruction")]
MultiQEncountered,
#[error(
"A connected component of the DAGCircuit is too large for any of the connected components in the coupling map."
)]
MismatchedComponentSize,
#[error(transparent)]
DAGCircuit(#[from] DAGError),
}

impl From<DisjointLayoutError> for PyErr {
fn from(value: DisjointLayoutError) -> Self {
match value {
DisjointLayoutError::MultiQEncountered => MultiQEncountered::new_err(""),
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DisjointLayoutError::MismatchedComponentSize => {
TranspilerError::new_err(value.to_string())
}
DisjointLayoutError::DAGCircuit(dagerror) => dagerror.into(),
}
}
}

static COUPLING_MAP: ImportOnceCell =
ImportOnceCell::new("qiskit.transpiler.coupling", "CouplingMap");

Expand Down Expand Up @@ -86,7 +111,7 @@ fn subgraph(graph: &CouplingMap, node_set: &HashSet<NodeIndex>) -> CouplingMap {
}

#[pyfunction(name = "run_pass_over_connected_components")]
pub fn py_run_pass_over_connected_components(
fn py_run_pass_over_connected_components(
dag: Bound<DAGCircuit>,
target: &Target,
run_func: Bound<PyAny>,
Expand Down Expand Up @@ -159,18 +184,18 @@ pub fn py_run_pass_over_connected_components(
}
}

pub fn distribute_components(dag: &mut DAGCircuit, target: &Target) -> PyResult<DisjointSplit> {
pub fn distribute_components(
dag: &mut DAGCircuit,
target: &Target,
) -> Result<DisjointSplit, DisjointLayoutError> {
let coupling_map: CouplingMap = match build_coupling_map(target) {
Some(map) => map,
None => return Ok(DisjointSplit::NoneNeeded),
};
let cmap_components = connected_components(&coupling_map);
if cmap_components.len() == 1 {
if dag.num_qubits() > cmap_components[0].len() {
return Err(TranspilerError::new_err(concat!(
"A connected component of the DAGCircuit is too large for any of the connected ",
"components in the coupling map."
)));
return Err(DisjointLayoutError::MismatchedComponentSize);
}
return Ok(DisjointSplit::NoneNeeded);
}
Expand Down Expand Up @@ -251,7 +276,7 @@ pub fn distribute_components(dag: &mut DAGCircuit, target: &Target) -> PyResult<
let subgraph = subgraph(&coupling_map, &cmap_components[cmap_index]);
Ok((out_dag, subgraph))
})
.collect::<PyResult<Vec<_>>>()?;
.collect::<Result<Vec<_>, DAGError>>()?;
if out_component_pairs.len() == 1 {
return Ok(DisjointSplit::TargetSubset(
out_component_pairs[0]
Expand Down Expand Up @@ -288,7 +313,7 @@ pub fn distribute_components(dag: &mut DAGCircuit, target: &Target) -> PyResult<
fn map_components(
dag_components: &[DAGCircuit],
cmap_components: &[HashSet<NodeIndex>],
) -> PyResult<Vec<Vec<usize>>> {
) -> Result<Vec<Vec<usize>>, DisjointLayoutError> {
let mut free_qubits: Vec<usize> = cmap_components.iter().map(|g| g.len()).collect();
let mut out_mapping = vec![Vec::new(); cmap_components.len()];
let mut dag_qubits: Vec<(usize, usize)> = dag_components
Expand All @@ -312,9 +337,7 @@ fn map_components(
}
}
if !found {
return Err(TranspilerError::new_err(
"A connected component of the DAGCircuit is too large for any of the connected components in the coupling map",
));
return Err(DisjointLayoutError::MismatchedComponentSize);
}
}
Ok(out_mapping)
Expand Down Expand Up @@ -361,7 +384,9 @@ struct InteractionGraphData<Ty: EdgeType> {
reverse_im_graph_node_map: Vec<Option<Qubit>>,
}

fn generate_directed_interaction(dag: &DAGCircuit) -> PyResult<InteractionGraphData<Directed>> {
fn generate_directed_interaction(
dag: &DAGCircuit,
) -> Result<InteractionGraphData<Directed>, DisjointLayoutError> {
let mut im_graph_node_map: Vec<Option<NodeIndex>> = vec![None; dag.num_qubits()];
let mut reverse_im_graph_node_map: Vec<Option<Qubit>> = vec![None; dag.num_qubits()];
let wire_map: Vec<Qubit> = (0..dag.num_qubits()).map(Qubit::new).collect();
Expand All @@ -385,7 +410,7 @@ fn build_interaction_graph<Ty: EdgeType>(
im_graph: &mut Graph<(), (), Ty>,
im_graph_node_map: &mut [Option<NodeIndex>],
reverse_im_graph_node_map: &mut [Option<Qubit>],
) -> PyResult<()> {
) -> Result<(), DisjointLayoutError> {
for (_, inst) in dag.op_nodes(false) {
if let Some(control_flow) = dag.try_view_control_flow(inst) {
for block in control_flow.blocks() {
Expand Down Expand Up @@ -444,13 +469,13 @@ fn build_interaction_graph<Ty: EdgeType>(
}
}
if len_args > 2 {
return Err(MultiQEncountered::new_err(""));
return Err(DisjointLayoutError::MultiQEncountered);
}
}
Ok(())
}

fn separate_dag(dag: &mut DAGCircuit) -> PyResult<Vec<DAGCircuit>> {
fn separate_dag(dag: &mut DAGCircuit) -> Result<Vec<DAGCircuit>, DisjointLayoutError> {
split_barriers(dag)?;
let im_graph_data = generate_directed_interaction(dag)?;
let connected_components = connected_components(&im_graph_data.im_graph);
Expand All @@ -464,9 +489,9 @@ fn separate_dag(dag: &mut DAGCircuit) -> PyResult<Vec<DAGCircuit>> {
})
.collect();
let qubits: HashSet<Qubit> = (0..dag.num_qubits()).map(Qubit::new).collect();
let decomposed_dags: PyResult<Vec<DAGCircuit>> = component_qubits
let decomposed_dags: Result<Vec<DAGCircuit>, DAGError> = component_qubits
.into_iter()
.map(|dag_qubits| -> PyResult<DAGCircuit> {
.map(|dag_qubits| -> Result<DAGCircuit, DAGError> {
let mut new_dag = dag.copy_empty_like(VarsMode::Alike, BlocksMode::Drop)?;
let qubits_to_revmove: Vec<Qubit> = qubits.difference(&dag_qubits).copied().collect();

Expand Down Expand Up @@ -517,11 +542,11 @@ fn separate_dag(dag: &mut DAGCircuit) -> PyResult<Vec<DAGCircuit>> {
})
.collect();
combine_barriers(dag, false)?;
decomposed_dags
decomposed_dags.map_err(Into::into)
}

#[pyfunction]
pub fn combine_barriers(dag: &mut DAGCircuit, retain_uuid: bool) -> PyResult<()> {
pub fn combine_barriers(dag: &mut DAGCircuit, retain_uuid: bool) -> Result<(), DAGError> {
let mut uuid_map: HashMap<String, NodeIndex> = HashMap::new();
let barrier_nodes: Vec<NodeIndex> = dag
.op_nodes(true)
Expand Down Expand Up @@ -575,7 +600,7 @@ pub fn combine_barriers(dag: &mut DAGCircuit, retain_uuid: bool) -> PyResult<()>
Ok(())
}

fn split_barriers(dag: &mut DAGCircuit) -> PyResult<()> {
fn split_barriers(dag: &mut DAGCircuit) -> Result<(), DAGError> {
for (_index, inst) in dag.op_nodes(true) {
let OperationRef::StandardInstruction(StandardInstruction::Barrier(num_qubits)) =
inst.op.view()
Expand Down
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