Fix subgraph isomorphism (petgraph#472)

* Fix subgraph isomorphism * Run rustfmt
teuron · Oct 9, 2022 · 12f1d33 · 12f1d33
1 parent e3e13e1
commit 12f1d33
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Showing 2 changed files with 15 additions and 6 deletions.
diff --git a/src/algo/isomorphism.rs b/src/algo/isomorphism.rs
@@ -555,6 +555,7 @@ mod matching {
         mut st: &mut (Vf2State<'_, G0>, Vf2State<'_, G1>),
         node_match: &mut NM,
         edge_match: &mut EM,
+        match_subgraph: bool,
     ) -> Option<bool>
     where
         G0: NodeCompactIndexable
@@ -611,7 +612,13 @@ mod matching {
                             return Some(true);
                         }
                         // Check cardinalities of Tin, Tout sets
-                        if st.0.out_size == st.1.out_size && st.0.ins_size == st.1.ins_size {
+                        if (!match_subgraph
+                            && st.0.out_size == st.1.out_size
+                            && st.0.ins_size == st.1.ins_size)
+                            || (match_subgraph
+                                && st.0.out_size <= st.1.out_size
+                                && st.0.ins_size <= st.1.ins_size)
+                        {
                             let f0 = Frame::Unwind { nodes, open_list };
                             stack.push(f0);
                             stack.push(Frame::Outer);
@@ -661,7 +668,8 @@ where
     }
 
     let mut st = (Vf2State::new(&g0), Vf2State::new(&g1));
-    self::matching::try_match(&mut st, &mut NoSemanticMatch, &mut NoSemanticMatch).unwrap_or(false)
+    self::matching::try_match(&mut st, &mut NoSemanticMatch, &mut NoSemanticMatch, false)
+        .unwrap_or(false)
 }
 
 /// \[Generic\] Return `true` if the graphs `g0` and `g1` are isomorphic.
@@ -697,7 +705,7 @@ where
     }
 
     let mut st = (Vf2State::new(&g0), Vf2State::new(&g1));
-    self::matching::try_match(&mut st, &mut node_match, &mut edge_match).unwrap_or(false)
+    self::matching::try_match(&mut st, &mut node_match, &mut edge_match, false).unwrap_or(false)
 }
 
 /// \[Generic\] Return `true` if `g0` is isomorphic to a subgraph of `g1`.
@@ -747,7 +755,8 @@ where
     }
 
     let mut st = (Vf2State::new(&g0), Vf2State::new(&g1));
-    self::matching::try_match(&mut st, &mut NoSemanticMatch, &mut NoSemanticMatch).unwrap_or(false)
+    self::matching::try_match(&mut st, &mut NoSemanticMatch, &mut NoSemanticMatch, true)
+        .unwrap_or(false)
 }
 
 /// \[Generic\] Return `true` if `g0` is isomorphic to a subgraph of `g1`.
@@ -783,5 +792,5 @@ where
     }
 
     let mut st = (Vf2State::new(&g0), Vf2State::new(&g1));
-    self::matching::try_match(&mut st, &mut node_match, &mut edge_match).unwrap_or(false)
+    self::matching::try_match(&mut st, &mut node_match, &mut edge_match, true).unwrap_or(false)
 }
diff --git a/tests/iso.rs b/tests/iso.rs
@@ -488,7 +488,7 @@ fn iso_multigraph_failure() {
 #[test]
 fn iso_subgraph() {
     let g0 = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0)]);
-    let g1 = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0), (2, 3)]);
+    let g1 = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0), (2, 3), (0, 4)]);
     assert!(!is_isomorphic(&g0, &g1));
     assert!(is_isomorphic_subgraph(&g0, &g1));
 }