Add louvain in compute facade

Author: IoannisPanagiotas

algo/src/main/java/org/neo4j/gds/louvain/LouvainResult.java

@@ -55,4 +55,12 @@ public long size() {
         return communities.size();
     }
 
+    public static LouvainResult EMPTY = new LouvainResult(
+        HugeLongArray.newArray(0),
+        0,
+        null,
+        new double[0],
+        0
+    );
+
 }

algorithms-compute-facade/src/main/java/org/neo4j/gds/community/CommunityComputeFacade.java

@@ -54,6 +54,9 @@
 import org.neo4j.gds.leiden.Leiden;
 import org.neo4j.gds.leiden.LeidenParameters;
 import org.neo4j.gds.leiden.LeidenResult;
+import org.neo4j.gds.louvain.Louvain;
+import org.neo4j.gds.louvain.LouvainParameters;
+import org.neo4j.gds.louvain.LouvainResult;
 import org.neo4j.gds.result.TimedAlgorithmResult;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficient;
@@ -413,5 +416,36 @@ CompletableFuture<TimedAlgorithmResult<LeidenResult>> leiden(
         );
     }
 
+    CompletableFuture<TimedAlgorithmResult<LouvainResult>> louvain(
+        Graph graph,
+        LouvainParameters parameters,
+        JobId jobId,
+        boolean logProgress
+    ) {
+
+        if (graph.isEmpty()) {
+            return CompletableFuture.completedFuture(TimedAlgorithmResult.empty(LouvainResult.EMPTY));
+        }
+
+        var progressTracker = progressTrackerFactory.create(
+            tasks.louvain(graph,parameters),
+            jobId,
+            parameters.concurrency(),
+            logProgress
+        );
+
+        var algorithm = new Louvain(
+            graph,
+            parameters,
+            progressTracker,
+            DefaultPool.INSTANCE,
+            terminationFlag
+        );
+
+        return algorithmCaller.run(
+            algorithm::compute,
+            jobId
+        );
+    }
 
 }

algorithms-compute-facade/src/test/java/org/neo4j/gds/community/CommunityComputeFacadeEmptyGraphTest.java

@@ -45,6 +45,8 @@
 import org.neo4j.gds.labelpropagation.LabelPropagationResult;
 import org.neo4j.gds.leiden.LeidenParameters;
 import org.neo4j.gds.leiden.LeidenResult;
+import org.neo4j.gds.louvain.LouvainParameters;
+import org.neo4j.gds.louvain.LouvainResult;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientParameters;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientResult;
@@ -249,4 +251,21 @@ void leiden(){
         verifyNoInteractions(progressTrackerFactoryMock);
         verifyNoInteractions(algorithmCallerMock);
     }
+
+    @Test
+    void louvain(){
+
+        var future = facade.louvain(
+            graph,
+            mock(LouvainParameters.class),
+            jobIdMock,
+            false
+        );
+
+        var results = future.join();
+
+        assertThat(results.result()).isEqualTo(LouvainResult.EMPTY);
+        verifyNoInteractions(progressTrackerFactoryMock);
+        verifyNoInteractions(algorithmCallerMock);
+    }
 }

algorithms-compute-facade/src/test/java/org/neo4j/gds/community/CommunityComputeFacadeTest.java

@@ -47,6 +47,7 @@
 import org.neo4j.gds.labelpropagation.LabelPropagationParameters;
 import org.neo4j.gds.leiden.LeidenParameters;
 import org.neo4j.gds.logging.Log;
+import org.neo4j.gds.louvain.LouvainParameters;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientParameters;
 
@@ -313,4 +314,26 @@ void leiden(){
         assertThat(results.computeMillis()).isNotNegative();
     }
 
+    @Test
+    void louvain(){
+        var future = facade.louvain(
+            graph,
+            new LouvainParameters(
+                new Concurrency(4),
+                10,
+                0,
+                10,
+                false,
+                null
+            ),
+            jobIdMock,
+            false
+        );
+
+        var results = future.join();
+
+        assertThat(results.result().ranLevels()).isGreaterThan(0);
+        assertThat(results.computeMillis()).isNotNegative();
+    }
+
 }