[bugfix] Check for isolated nodes in `ConnectivityPredicate::implies(…

…)` (#286)
CQCL · Mar 11, 2022 · c9b726b · c9b726b
1 parent 92fc286
commit c9b726b
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diff --git a/pytket/docs/changelog.rst b/pytket/docs/changelog.rst
@@ -59,6 +59,11 @@ Minor new features:
   architecture constraints.
 * ``CircuitStatus`` has several new optional properties such as time-stamps associated with status changes,
   queue position or detailed error information.
+
+Fixes:
+
+* ``ConnectivityPredicate.implies()`` checks for existence of isolated nodes as
+  well as edges in second architecture.
 
 0.19.2 (February 2022)
 ----------------------

diff --git a/tket/src/Predicates/Predicates.cpp b/tket/src/Predicates/Predicates.cpp
@@ -17,6 +17,7 @@
 #include "Gate/Gate.hpp"
 #include "Mapping/Verification.hpp"
 #include "Placement/Placement.hpp"
+#include "Utils/UnitID.hpp"
 
 namespace tket {
 
@@ -332,6 +333,12 @@ bool ConnectivityPredicate::implies(const Predicate& other) const {
         dynamic_cast<const ConnectivityPredicate&>(other);
     const Architecture& arc1 = arch_;
     const Architecture& arc2 = other_c.arch_;
+    // Check that all nodes in arc1 are in arc2:
+    for (const Node& n : arc1.get_all_nodes_vec()) {
+      if (!arc2.node_exists(n)) {
+        return false;
+      }
+    }
     // Collect all edges in arc1
     for (auto [n1, n2] : arc1.get_all_edges_vec()) {
       if (!arc2.edge_exists(n1, n2) && !arc2.edge_exists(n2, n1)) {

diff --git a/tket/tests/test_Predicates.cpp b/tket/tests/test_Predicates.cpp
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <catch2/catch.hpp>
+#include <memory>
 
 #include "Placement/Placement.hpp"
 #include "Predicates/CompilationUnit.hpp"
@@ -186,10 +187,14 @@ SCENARIO("Test routing-related predicates' meet and implication") {
   Node n0("test", 0);
   Node n1("test", 1);
   Node n2("test", 2);
+  Node n3("test", 3);
   Architecture arc1({{n0, n1}, {n1, n2}});
   Architecture arc2({{n0, n1}, {n1, n2}, {n0, n2}});
   Architecture arc3({{n0, n2}, {n0, n1}});
   Architecture arc4({{n2, n0}, {n0, n1}});
+  Architecture arc5({n0, n1, n2, n3});
+  arc5.add_connection(n0, n1);
+  arc5.add_connection(n1, n2);
 
   Circuit circ(3);
   circ.add_op<unsigned>(OpType::CX, {0, 1});
@@ -205,11 +210,17 @@ SCENARIO("Test routing-related predicates' meet and implication") {
     PredicatePtr con2 = std::make_shared<ConnectivityPredicate>(arc2);
     PredicatePtr con3 = std::make_shared<ConnectivityPredicate>(arc3);
     PredicatePtr con4 = std::make_shared<ConnectivityPredicate>(arc4);
+    PredicatePtr con5 = std::make_shared<ConnectivityPredicate>(arc5);
     WHEN("Test implies") {
       REQUIRE(con1->implies(*con2));
       REQUIRE(con4->implies(*con3));  // directedness doesn't matter
       REQUIRE_FALSE(con1->implies(*con3));
     }
+    WHEN("Test implies (isolated nodes)") {
+      // https://github.com/CQCL/tket/issues/88
+      REQUIRE(con1->implies(*con5));
+      REQUIRE_FALSE(con5->implies(*con1));
+    }
     WHEN("Test meet") {
       PredicatePtr meet_a = con1->meet(*con2);
       REQUIRE(meet_a->verify(circ));