Merge branch 'main' into fix/getting-started-ibmq-run-device

Author: cqc-alec

TKET_VERSION

@@ -1 +1 @@
-2.1.102
+2.1.103

pytket/docs/changelog.md

@@ -6,6 +6,8 @@ Fixes:
 
 - Fix segfault in `LexiRouteRoutingMethod` (and so `DefaultMappingPass`) when
   a `ClExprOp` is reached while looking ahead to the next two-qubit slice.
+- Fix out-of-bounds accesses in `LinePlacement` for circuits with no two-qubit
+  interactions, and in Pauli partitioning with no terms.
 
 ## 2.18.4 (September 2026)
 

tket/src/Architecture/Architecture.cpp

@@ -112,6 +112,9 @@ static bool lexicographical_comparison(
 
 std::optional<Node> Architecture::find_worst_node(
     const Architecture& original_arch) {
+  if (n_nodes() == 0) {
+    return std::nullopt;
+  }
   node_set_t ap = get_articulation_points();
   node_set_t min_nodes = min_degree_nodes();
 

tket/src/Diagonalisation/PauliPartition.cpp

@@ -167,7 +167,7 @@ get_partitioned_paulis_for_largest_first_method(const PauliACGraph& pac_graph) {
       unsigned*,
       boost::property_map<PauliACGraph, boost::vertex_index_t>::const_type>
       colour_prop_map(
-          &colour_vec.front(), boost::get(boost::vertex_index, pac_graph));
+          colour_vec.data(), boost::get(boost::vertex_index, pac_graph));
   boost::sequential_vertex_coloring(
       pac_graph,
       boost::make_iterator_property_map(

tket/test/src/Placement/test_LinePlacement.cpp

@@ -24,8 +24,6 @@ SCENARIO("LinePlacement class") {
     REQUIRE_THROWS_AS(LinePlacement(architecture), std::logic_error);
   }
 
-// https://github.com/Quantinuum/tket/issues/2199
-#ifdef NDEBUG
   GIVEN("Empty circuit, two qubit Architecture, LinePlacement::Place.") {
     std::vector<std::pair<unsigned, unsigned>> edges = {{0, 1}};
     Architecture architecture(edges);
@@ -34,7 +32,6 @@ SCENARIO("LinePlacement class") {
     placement.place(circuit);
     REQUIRE(circuit.n_qubits() == 0);
   }
-#endif
 
   GIVEN("Single qubit circuit, two qubit Architecture, LinePlacement::Place") {
     std::vector<std::pair<unsigned, unsigned>> edges = {{0, 1}};

tket/test/src/test_Partition.cpp

@@ -32,8 +32,6 @@ SCENARIO("Small sets of Gadgets are partitioned correctly") {
       GraphColourMethod::LargestFirst, GraphColourMethod::Exhaustive,
       GraphColourMethod::Lazy};
 
-// https://github.com/Quantinuum/tket/issues/2199
-#ifdef NDEBUG
   GIVEN("No gadgets") {
     for (auto colouring_method : colouring_methods) {
       for (PauliPartitionStrat strat : strats) {
@@ -44,7 +42,6 @@ SCENARIO("Small sets of Gadgets are partitioned correctly") {
       }
     }
   }
-#endif
 
   GIVEN("Two anti-commuting gadgets") {
     /* We know the correct order, as QubitOperator orders