feat(algorithm): support random walk in computer

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/sampling/RandomWalk.java

@@ -0,0 +1,190 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You 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.apache.hugegraph.computer.algorithm.sampling;
+
+import org.apache.hugegraph.computer.core.common.exception.ComputerException;
+import org.apache.hugegraph.computer.core.config.Config;
+import org.apache.hugegraph.computer.core.graph.edge.Edge;
+import org.apache.hugegraph.computer.core.graph.edge.Edges;
+import org.apache.hugegraph.computer.core.graph.id.Id;
+import org.apache.hugegraph.computer.core.graph.value.IdList;
+import org.apache.hugegraph.computer.core.graph.value.IdListList;
+import org.apache.hugegraph.computer.core.graph.vertex.Vertex;
+import org.apache.hugegraph.computer.core.worker.Computation;
+import org.apache.hugegraph.computer.core.worker.ComputationContext;
+import org.apache.hugegraph.util.Log;
+import org.slf4j.Logger;
+
+import java.util.Iterator;
+import java.util.Random;
+
+public class RandomWalk implements Computation<RandomWalkMessage> {
+
+    private static final Logger LOG = Log.logger(RandomWalk.class);
+
+    public static final String OPTION_WALK_PER_NODE = "randomwalk.walk_per_node";
+    public static final String OPTION_WALK_LENGTH = "randomwalk.walk_length";
+
+    /**
+     * number of times per vertex(source vertex) walks
+     */
+    private Integer walkPerNode;
+
+    /**
+     * walk length
+     */
+    private Integer walkLength;
+
+    /**
+     * random
+     */
+    private Random random;
+
+    @Override
+    public String category() {
+        return "sampling";
+    }
+
+    @Override
+    public String name() {
+        return "random_walk";
+    }
+
+    @Override
+    public void init(Config config) {
+        this.walkPerNode = config.getInt(OPTION_WALK_PER_NODE, 3);
+        if (this.walkPerNode <= 0) {
+            throw new ComputerException("The param %s must be greater than 0, " +
+                    "actual got '%s'",
+                    OPTION_WALK_PER_NODE, this.walkPerNode);
+        }
+        LOG.info("[RandomWalk] algorithm param, {}: {}", OPTION_WALK_PER_NODE, walkPerNode);
+
+        this.walkLength = config.getInt(OPTION_WALK_LENGTH, 3);
+        if (this.walkLength <= 0) {
+            throw new ComputerException("The param %s must be greater than 0, " +
+                    "actual got '%s'",
+                    OPTION_WALK_LENGTH, this.walkLength);
+        }
+        LOG.info("[RandomWalk] algorithm param, {}: {}", OPTION_WALK_LENGTH, walkLength);
+
+        this.random = new Random();
+    }
+
+    @Override
+    public void compute0(ComputationContext context, Vertex vertex) {
+        vertex.value(new IdListList());
+
+        RandomWalkMessage message = new RandomWalkMessage();
+        message.addToPath(vertex);
+
+        if (vertex.numEdges() <= 0) {
+            // isolated vertex
+            this.savePath(vertex, message.path()); // save result
+            vertex.inactivate();
+            return;
+        }
+
+        for (int i = 0; i < walkPerNode; ++i) {
+            // random select one edge and walk
+            Edge selectedEdge = this.randomSelectEdge(vertex.edges());
+            context.sendMessage(selectedEdge.targetId(), message);
+        }
+    }
+
+    @Override
+    public void compute(ComputationContext context, Vertex vertex,
+                        Iterator<RandomWalkMessage> messages) {
+        while (messages.hasNext()) {
+            RandomWalkMessage message = messages.next();
+
+            if (message.isFinish()) {
+                this.savePath(vertex, message.path()); // save result
+
+                vertex.inactivate();
+                continue;
+            }
+
+            message.addToPath(vertex);
+
+            if (vertex.numEdges() <= 0) {
+                // there is nowhere to walk，finish eariler
+                message.finish();
+                context.sendMessage(this.getSourceId(message.path()), message);
+
+                vertex.inactivate();
+                continue;
+            }
+
+            if (message.path().size() >= this.walkLength + 1) {
+                message.finish();
+                Id sourceId = this.getSourceId(message.path());
+
+                if (vertex.id().equals(sourceId)) {
+                    // current vertex is the source vertex，no need to send message once more
+                    this.savePath(vertex, message.path()); // save result
+                } else {
+                    context.sendMessage(sourceId, message);
+                }
+
+                vertex.inactivate();
+                continue;
+            }
+
+            // random select one edge and walk
+            Edge selectedEdge = this.randomSelectEdge(vertex.edges());
+            context.sendMessage(selectedEdge.targetId(), message);
+        }
+    }
+
+    /**
+     * random select one edge
+     */
+    private Edge randomSelectEdge(Edges edges) {
+        Edge selectedEdge = null;
+        int randomNum = random.nextInt(edges.size());
+
+        int i = 0;
+        Iterator<Edge> iterator = edges.iterator();
+        while (iterator.hasNext()) {
+            selectedEdge = iterator.next();
+            if (i == randomNum) {
+                break;
+            }
+            i++;
+        }
+
+        return selectedEdge;
+    }
+
+    /**
+     * get source id of path
+     */
+    private Id getSourceId(IdList path) {
+        // the first id of path is the source id
+        return path.get(0);
+    }
+
+    /**
+     * save path
+     */
+    private void savePath(Vertex sourceVertex, IdList path) {
+        IdListList curValue = sourceVertex.value();
+        curValue.add(path.copy());
+    }
+}

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/sampling/RandomWalkMessage.java

@@ -0,0 +1,79 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You 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.apache.hugegraph.computer.algorithm.sampling;
+
+import org.apache.hugegraph.computer.core.graph.value.BooleanValue;
+import org.apache.hugegraph.computer.core.graph.value.IdList;
+import org.apache.hugegraph.computer.core.graph.value.Value;
+import org.apache.hugegraph.computer.core.graph.vertex.Vertex;
+import org.apache.hugegraph.computer.core.io.RandomAccessInput;
+import org.apache.hugegraph.computer.core.io.RandomAccessOutput;
+
+import java.io.IOException;
+import java.util.List;
+
+public class RandomWalkMessage implements Value.CustomizeValue<List<Object>> {
+
+    /**
+     * random walk path
+     */
+    private final IdList path;
+
+    /**
+     * finish flag
+     */
+    private BooleanValue isFinish;
+
+    public RandomWalkMessage() {
+        this.path = new IdList();
+        this.isFinish = new BooleanValue(false);
+    }
+
+    @Override
+    public void read(RandomAccessInput in) throws IOException {
+        this.path.read(in);
+        this.isFinish.read(in);
+    }
+
+    @Override
+    public void write(RandomAccessOutput out) throws IOException {
+        this.path.write(out);
+        this.isFinish.write(out);
+    }
+
+    @Override
+    public List<Object> value() {
+        return this.path.value();
+    }
+
+    public IdList path() {
+        return this.path;
+    }
+
+    public void addToPath(Vertex vertex) {
+        this.path.add(vertex.id());
+    }
+
+    public boolean isFinish() {
+        return this.isFinish.boolValue();
+    }
+
+    public void finish() {
+        this.isFinish = new BooleanValue(true);
+    }
+}

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/sampling/RandomWalkOutput.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You 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.apache.hugegraph.computer.algorithm.sampling;
+
+import org.apache.hugegraph.computer.core.graph.value.IdListList;
+import org.apache.hugegraph.computer.core.graph.vertex.Vertex;
+import org.apache.hugegraph.computer.core.output.hg.HugeGraphOutput;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class RandomWalkOutput extends HugeGraphOutput<List<String>> {
+
+    @Override
+    protected void prepareSchema() {
+        this.client().schema().propertyKey(this.name())
+                .asText()
+                .writeType(this.writeType())
+                .valueList()
+                .ifNotExist()
+                .create();
+    }
+
+    @Override
+    protected List<String> value(Vertex vertex) {
+        IdListList value = vertex.value();
+        List<String> propValues = new ArrayList<>();
+        for (int i = 0; i < value.size(); i++) {
+            propValues.add(value.get(i).toString());
+        }
+        return propValues;
+    }
+}

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/sampling/RandomWalkParams.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You 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.apache.hugegraph.computer.algorithm.sampling;
+
+import org.apache.hugegraph.computer.algorithm.AlgorithmParams;
+import org.apache.hugegraph.computer.core.config.ComputerOptions;
+import org.apache.hugegraph.computer.core.graph.value.IdListList;
+
+import java.util.Map;
+
+public class RandomWalkParams implements AlgorithmParams {
+
+    @Override
+    public void setAlgorithmParameters(Map<String, String> params) {
+        this.setIfAbsent(params, ComputerOptions.WORKER_COMPUTATION_CLASS,
+                RandomWalk.class.getName());
+        this.setIfAbsent(params, ComputerOptions.ALGORITHM_MESSAGE_CLASS,
+                RandomWalkMessage.class.getName());
+        this.setIfAbsent(params, ComputerOptions.ALGORITHM_RESULT_CLASS,
+                IdListList.class.getName());
+        this.setIfAbsent(params, ComputerOptions.OUTPUT_CLASS,
+                RandomWalkOutput.class.getName());
+
+        this.setIfAbsent(params, RandomWalk.OPTION_WALK_PER_NODE, "3");
+        this.setIfAbsent(params, RandomWalk.OPTION_WALK_LENGTH, "3");
+    }
+}

computer-test/src/main/java/org/apache/hugegraph/computer/algorithm/AlgorithmTestSuite.java

@@ -28,6 +28,7 @@
 import org.apache.hugegraph.computer.algorithm.community.wcc.WccTest;
 import org.apache.hugegraph.computer.algorithm.path.rings.RingsDetectionTest;
 import org.apache.hugegraph.computer.algorithm.path.rings.RingsDetectionWithFilterTest;
+import org.apache.hugegraph.computer.algorithm.sampling.RandomWalkTest;
 import org.junit.runner.RunWith;
 import org.junit.runners.Suite;
 
@@ -43,7 +44,8 @@
     RingsDetectionWithFilterTest.class,
     ClusteringCoefficientTest.class,
     ClosenessCentralityTest.class,
-    BetweennessCentralityTest.class
+    BetweennessCentralityTest.class,
+    RandomWalkTest.class
 })
 public class AlgorithmTestSuite {
 }