[dbs-leipzig#1570] add help functions

gradoop-temporal/src/main/java/org/gradoop/temporal/model/impl/operators/metric/functions/ExtractAllTimePointsReduce.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.gradoop.temporal.model.impl.operators.metric.functions;
+
+import org.apache.flink.api.common.functions.GroupReduceFunction;
+import org.apache.flink.api.java.tuple.Tuple1;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.util.Collector;
+import org.gradoop.common.model.impl.id.GradoopId;
+
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+
+/**
+ * Reduce function to extract all timestamps where the degree of a vertex changes.
+ */
+public class ExtractAllTimePointsReduce implements GroupReduceFunction<Tuple2<GradoopId, TreeMap<Long, Integer>>, Tuple1<Long>> {
+
+    public ExtractAllTimePointsReduce() {
+    }
+
+    @Override
+    public void reduce(Iterable<Tuple2<GradoopId, TreeMap<Long, Integer>>> iterable, Collector<Tuple1<Long>> collector) throws Exception {
+        SortedSet<Long> timePoints = new TreeSet<>();
+
+        for (Tuple2<GradoopId, TreeMap<Long, Integer>> tuple : iterable) {
+            timePoints.addAll(tuple.f1.keySet());
+        }
+
+        for (Long timePoint: timePoints) {
+            collector.collect(new Tuple1<>(timePoint));
+        }
+
+    }
+}

gradoop-temporal/src/main/java/org/gradoop/temporal/model/impl/operators/metric/functions/TransformDeltaToAbsoluteDegreeTree.java

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+/*
+ * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.gradoop.temporal.model.impl.operators.metric.functions;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.java.functions.FunctionAnnotation;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.gradoop.common.model.impl.id.GradoopId;
+
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * Replaces the degree tree, that just stores the degree changes for each time, with a degree tree that
+ * stores the actual degree of the vertex at that time.
+ */
+@FunctionAnnotation.ForwardedFields("f0")
+public class TransformDeltaToAbsoluteDegreeTree
+        implements MapFunction<Tuple2<GradoopId, TreeMap<Long, Integer>>,
+        Tuple2<GradoopId, TreeMap<Long, Integer>>> {
+
+    /**
+     * To reduce object instantiations.
+     */
+    private TreeMap<Long, Integer> absoluteDegreeTree;
+
+    @Override
+    public Tuple2<GradoopId, TreeMap<Long, Integer>> map(
+            Tuple2<GradoopId, TreeMap<Long, Integer>> vIdTreeMapTuple) throws Exception {
+        // init the degree and the temporal tree
+        int degree = 0;
+        absoluteDegreeTree = new TreeMap<>();
+
+        // aggregate the degrees
+        for (Map.Entry<Long, Integer> entry : vIdTreeMapTuple.f1.entrySet()) {
+            degree += entry.getValue();
+            absoluteDegreeTree.put(entry.getKey(), degree);
+        }
+        vIdTreeMapTuple.f1 = absoluteDegreeTree;
+        return vIdTreeMapTuple;
+    }
+}