Refactor graph traversal methods to use new `computeTraversalPartitions` API by clementleclercRTE · Pull Request #3753 · powsybl/powsybl-core

clementleclercRTE · 2026-02-03T08:34:05Z

Please check if the PR fulfills these requirements

The commit message follows our guidelines
Tests for the changes have been added (for bug fixes / features)
Docs have been added / updated (for bug fixes / features)
[ ] A PR or issue has been opened in all impacted repositories (if any)

Does this PR already have an issue describing the problem?

What kind of change does this PR introduce?

Refactoring / New API

What is the current behavior?

Currently, BusBreakerTopologyModel, NodeBreakerTopologyModel, and DcTopologyModel all contain duplicated logic to traverse the graph and identify connected components (bus construction).

What is the new behavior (if this is a feature change)?

A new method computeTraversalPartitions has been introduced in the UndirectedGraph interface. It centralizes the graph traversal and connected component building logic, using standard
functional interfaces (Supplier, ObjIntConsumer) for flexibility. The three topology models have been refactored to use this shared method.

The previously public method traverse(int, TraversalType, Traverser, boolean[]) is now deprecated in favor of traverse(int, TraversalType, Traverser) and
computeTraversalPartitions(...).

Does this PR introduce a breaking change or deprecate an API?

Yes
No

If yes, please check if the following requirements are fulfilled

The Breaking Change or Deprecated label has been added
The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

1. Deprecated: traverse(int, TraversalType, Traverser, boolean[])

If you were using this overload to manually track visited vertices, switch to the standard traverse(int, TraversalType, Traverser) overload. Visited vertices can be captured directly inside your
Traverser lambda.

2. Manual connected component computation

If you were manually implementing the traversal-and-partition pattern (iterating over vertices, tracking visited state, grouping results), you can now replace this logic with a call to
computeTraversalPartitions(Traverser) or its generic overload computeTraversalPartitions(Traverser, Supplier<C>, ObjIntConsumer<C>).

Other information:

…API. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

… graph-connected-components # Conflicts: # iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/NodeBreakerTopologyModel.java

math/src/main/java/com/powsybl/math/graph/UndirectedGraph.java

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

… traversal components. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

…Predicate` Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

…` API, and enhance vertex object handling in graph traversal implementations. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

sonarqubecloud · 2026-02-09T10:19:30Z

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

… graph-connected-components

iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/BusBreakerTopologyModel.java

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/BusBreakerTopologyModel.java

flo-dup · 2026-02-09T14:28:20Z

iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/NodeBreakerTopologyModel.java

+                }
+                return TraverseResult.CONTINUE;
+            }).forEach(nodes -> {
+                CopyOnWriteArrayList<NodeTerminal> terminals = new CopyOnWriteArrayList<>();


I'm wondering if we really need the CopyOnWriteArrayList for buses

iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/NodeBreakerTopologyModel.java

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

…comments Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

… graph-connected-components

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

flo-dup

The naming is questionable, as we're not computing connected component if we rely on graph theory definition. We should rather call it something like computeTraversalPartitions, as we're partitioning the graph (all the vertices are traversed if there's no TERMINATE_TRAVERSER return) based on a given traversal.

math/src/main/java/com/powsybl/math/graph/UndirectedGraph.java

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

flo-dup · 2026-02-23T15:06:26Z

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

+                C component = collector.createComponent();
+                collector.addVertex(component, v);
+
+                traverse(v, TraversalType.BREADTH_FIRST, (v1, e, v2) -> {


If traverse returns false, shouldn't we break?

Fixed. Note that TERMINATE_TRAVERSER should not normally be used here.
Using TERMINATE_TRAVERSER would result in an incomplete partition. The break is just a safety net.

Your note should be included in the javadoc of computeTraversalPartitions

… graph-connected-components

… update related tests, topology models, and traversal logic. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

…nents

flo-dup · 2026-03-03T13:40:04Z

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java


    private void traverseVertex(int vToTraverse, boolean[] vEncountered, Deque<DirectedEdge> edgesToTraverse,
-                                TIntArrayList[] adjacencyList, TraversalType traversalType) {
+                                TIntArrayList[] adjacencyList, TraversalType traversalType, @Nullable IntConsumer vertexVisitor) {


we usually don't need nullability annotations on private methods. Besides, a nullable functional interface is creating unnecessary complexity (my bad, I suggested you to do so in a previous comment!), you'd rather use a no-op IntConsumer instead of null

flo-dup · 2026-03-03T13:41:13Z

math/src/test/java/com/powsybl/math/graph/UndirectedGraphImplTest.java

Remove the use of the deprecated traverse in tests

flo-dup · 2026-03-03T13:48:27Z

iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/DcTopologyModel.java

+                    if (sw != null && sw.isOpen()) {
+                        return TraverseResult.TERMINATE_PATH;
                    }
+                    return TraverseResult.CONTINUE;


An edge cannot be null in DcTopologyModel

Suggested change

if (sw != null && sw.isOpen()) {

return TraverseResult.TERMINATE_PATH;

}

return TraverseResult.CONTINUE;

return sw.isOpen() ? TraverseResult.TERMINATE_PATH : TraverseResult.CONTINUE;

flo-dup · 2026-03-03T14:13:42Z

math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java

+    }
+
+    private boolean traverse(int v, TraversalType traversalType, Traverser traverser, boolean[] encounteredVertices, boolean[] encounteredEdges) {
+        return traverse(v, traversalType, traverser, encounteredVertices, encounteredEdges, null);


Suggested change

return traverse(v, traversalType, traverser, encounteredVertices, encounteredEdges, null);

return traverse(v, traversalType, traverser, encounteredVertices, encounteredEdges, vIndex -> {});

flo-dup · 2026-03-03T14:37:01Z

math/src/main/java/com/powsybl/math/graph/UndirectedGraph.java

-
-        void addVertex(C component, int vertexIndex);
-    }
+    <C> List<C> computeTraversalPartitions(Traverser traverser, Supplier<C> partitionFactory, ObjIntConsumer<C> vertexConsumer);


You need to add javadoc to explain clearly the method and the parameters.
Besides, rename vertexConsumer into something more explicit (vertexCollector?)

flo-dup · 2026-03-03T15:30:22Z

Could you also complete the PR description, regarding the migration guide / breaking changes part?

… graph-connected-components

…nents

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

sonarqubecloud · 2026-03-09T12:08:00Z

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
93.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

clementleclercRTE added 4 commits February 3, 2026 09:01

Refactor graph traversal methods to use new getConnectedComponents …

988efdd

…API. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Refactor graph traversal methods to use new getConnectedComponents …

30cc260

…API. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Merge remote-tracking branch 'origin/graph-connected-components' into…

10555c9

… graph-connected-components # Conflicts: # iidm/iidm-impl/src/main/java/com/powsybl/iidm/network/impl/NodeBreakerTopologyModel.java

Merge branch 'main' into graph-connected-components

e522228

flo-dup requested changes Feb 3, 2026

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rolnico changed the title ~~Refactor graph traversal methods to use new getConnectedComponents …~~ Refactor graph traversal methods to use new getConnectedComponents API Feb 3, 2026

flo-dup requested changes Feb 3, 2026

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math/src/main/java/com/powsybl/math/graph/UndirectedGraphImpl.java Outdated Show resolved Hide resolved

clementleclercRTE added 5 commits February 4, 2026 08:58

Remove isComponentValid method and inline validation logic in graph…

caa146e

… traversal components. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Refactor getConnectedComponents API to use Traverser instead of `…

b54a1c6

…Predicate` Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Deprecate old traversal method, simplify `ConnectedComponentCollector…

8eb3d6c

…` API, and enhance vertex object handling in graph traversal implementations. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Refactor getConnectedComponents usage

c562c12

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Merge branch 'main' into graph-connected-components

c9cf18d

clementleclercRTE requested a review from flo-dup February 4, 2026 13:03

Refactor traversal methods and update internal connection tests.

df1cf80

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

clementleclercRTE added 3 commits February 9, 2026 11:23

Merge branch 'main' into graph-connected-components

1b58640

Add unit tests for getConnectedComponents and update traversal logic

c5a2ef6

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Merge remote-tracking branch 'origin/graph-connected-components' into…

7cd03d4

… graph-connected-components

flo-dup requested changes Feb 9, 2026

View reviewed changes

clementleclercRTE added 5 commits February 10, 2026 17:02

Refactor topology models to replace Set with List and fix review …

16a1dd0

…comments Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Refactor topology models to replace Set with List and fix review …

e3e8b9e

…comments Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Merge remote-tracking branch 'origin/graph-connected-components' into…

037e516

… graph-connected-components

Merge branch 'main' into graph-connected-components

b173fb9

Fix indentation

201fb81

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

clementleclercRTE requested a review from flo-dup February 16, 2026 08:51

clementleclercRTE added 3 commits February 18, 2026 09:43

Merge branch 'main' into graph-connected-components

f73819e

Merge branch 'main' into graph-connected-components

583b71a

Merge branch 'main' into graph-connected-components

f85d061

flo-dup requested changes Feb 23, 2026

View reviewed changes

Merge remote-tracking branch 'origin/graph-connected-components' into…

dd565cb

… graph-connected-components

clementleclercRTE added 2 commits February 24, 2026 10:51

Refactor getConnectedComponents to computeTraversalPartitions and…

9557084

… update related tests, topology models, and traversal logic. Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

Merge remote-tracking branch 'origin/main' into graph-connected-compo…

8f96dea

…nents

flo-dup changed the title ~~Refactor graph traversal methods to use new getConnectedComponents API~~ Refactor graph traversal methods to use new computeTraversalPartitions API Mar 3, 2026

Merge branch 'main' into graph-connected-components

b6b5556

flo-dup requested changes Mar 3, 2026

View reviewed changes

clementleclercRTE added 3 commits March 9, 2026 09:26

Merge remote-tracking branch 'origin/graph-connected-components' into…

6c094d8

… graph-connected-components

Merge remote-tracking branch 'origin/main' into graph-connected-compo…

e7cbba1

…nents

review fix

8f84c9a

Signed-off-by: Leclerc Clement <clement.leclerc@rte-france.com>

clementleclercRTE added the Deprecated Methods have been deprecated label Mar 9, 2026

	return traverse(v, traversalType, traverser, encounteredVertices, encounteredEdges, null);
	return traverse(v, traversalType, traverser, encounteredVertices, encounteredEdges, vIndex -> {});

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