Github user vasia commented on a diff in the pull request:
https://github.com/apache/flink/pull/1329#discussion_r44008025
--- Diff: docs/libs/gelly_guide.md ---
@@ -485,13 +485,15 @@ val networkWithWeights =
network.joinWithEdgesOnSource(vertexOutDegrees, (v1: Do
* <strong>Undirected</strong>: In Gelly, a `Graph` is always directed.
Undirected graphs can be represented by adding all opposite-direction edges to
a graph. For this purpose, Gelly provides the `getUndirected()` method.
-* <strong>Union</strong>: Gelly's `union()` method performs a union
operation on the vertex and edge sets of the specified graph and current graph.
Duplicate vertices are removed from the resulting `Graph`, while if duplicate
edges exists, these will be maintained.
+* <strong>Union</strong>: Gelly's `union()` method performs an union
operation on the vertex and edge sets of the specified graph and the current
graph. Duplicate vertices are removed from the resulting `Graph`, while if
duplicate edges exists, these will be maintained.
<p class="text-center">
<img alt="Union Transformation" width="50%" src="fig/gelly-union.png"/>
</p>
-* <strong>Difference</strong>: Gelly's `difference()` method performs a
difference on the vertex and edge sets of the current graph and specified graph.
+* <strong>Difference</strong>: Gelly's `difference()` method performs a
difference on the vertex and edge sets of the current graph and the specified
graph.
+
+* <strong>Intersect</strong>: Gelly's `intersect()` method performs an
intersect on the edge sets of the current graph and the specified graph. Edges
are considered equal, if they have the same source identifier, target
identifier and edge value. Vertex values are replaced with `NullValue` and,
depending on a parameter, matching edges are either contained once in the
resulting `Graph` or as often as there are matching edge pairs between the
input graphs.
--- End diff --
I would add something like the following after the first paragraph: "The
result is a new Graph that contains the edges that are common in the two input
Graphs. Two edges are considered common ..."
Vertex values are replaced with NullValue => The result is a Graph with no
vertex values. And maybe give a hint on how one can retrieve the vertex values
if they want to?
depending on a parameter => can you explain what is this parameter and how
it works?
matching => common?
An small code example of the 2 alternatives might be helpful here :)
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