feat(algorithm): support single source shortest path algorithm

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/path/shortest/ShortestPathCombiner.java

@@ -0,0 +1,30 @@
+/*
+ * 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.path.shortest;
+
+import org.apache.hugegraph.computer.core.combiner.Combiner;
+
+public class ShortestPathCombiner implements Combiner<ShortestPathMessage> {
+
+    @Override
+    public void combine(ShortestPathMessage v1, ShortestPathMessage v2,
+                        ShortestPathMessage result) {
+        ShortestPathMessage message = v2.totalWeight() < v1.totalWeight() ? v2 : v1;
+        result.value(message);
+    }
+}

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/path/shortest/ShortestPathMessage.java

@@ -0,0 +1,102 @@
+/*
+ * 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.path.shortest;
+
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.hugegraph.computer.core.graph.value.DoubleValue;
+import org.apache.hugegraph.computer.core.graph.value.IdList;
+import org.apache.hugegraph.computer.core.graph.value.ListValue;
+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;
+
+public class ShortestPathMessage implements Value.CustomizeValue<List<Object>> {
+
+    /**
+     * path
+     */
+    private final IdList path;
+
+    /**
+     * weight of path
+     */
+    private final ListValue<DoubleValue> pathWeight;
+
+    public ShortestPathMessage() {
+        this.path = new IdList();
+        this.pathWeight = new ListValue<DoubleValue>();
+    }
+
+    @Override
+    public void read(RandomAccessInput in) throws IOException {
+        this.path.read(in);
+        this.pathWeight.read(in);
+    }
+
+    @Override
+    public void write(RandomAccessOutput out) throws IOException {
+        this.path.write(out);
+        this.pathWeight.write(out);
+    }
+
+    @Override
+    public List<Object> value() {
+        return this.path.value();
+    }
+
+    public void value(ShortestPathMessage message) {
+        this.path.clear();
+        this.pathWeight.clear();
+
+        this.path.addAll(message.path().copy().values());
+        this.pathWeight.addAll(message.pathWeight().copy().values());
+    }
+
+    public void addToPath(Vertex vertex, double weight) {
+        this.path.add(vertex.id());
+        this.pathWeight.add(new DoubleValue(weight));
+    }
+
+    public void addToPath(IdList path, ListValue<DoubleValue> pathWeight,
+                          Vertex vertex, double weight) {
+        this.path.addAll(path.copy().values());
+        this.pathWeight.addAll(pathWeight.copy().values());
+
+        this.path.add(vertex.id());
+        this.pathWeight.add(new DoubleValue(weight));
+    }
+
+    public IdList path() {
+        return this.path;
+    }
+
+    public ListValue<DoubleValue> pathWeight() {
+        return this.pathWeight;
+    }
+
+    public double totalWeight() {
+        double totalWeight = 0;
+        for (int i = 0; i < this.pathWeight.size(); ++i) {
+            totalWeight += this.pathWeight.get(i).doubleValue();
+        }
+        return totalWeight;
+    }
+}

computer-algorithm/src/main/java/org/apache/hugegraph/computer/algorithm/path/shortest/ShortestPathValue.java

@@ -0,0 +1,110 @@
+/*
+ * 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.path.shortest;
+
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.hugegraph.computer.core.graph.value.DoubleValue;
+import org.apache.hugegraph.computer.core.graph.value.IdList;
+import org.apache.hugegraph.computer.core.graph.value.ListValue;
+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;
+
+public class ShortestPathValue implements Value.CustomizeValue<List<Object>> {
+
+    /**
+     * path
+     */
+    private final IdList path;
+
+    /**
+     * weight of path
+     */
+    private final ListValue<DoubleValue> pathWeight;
+
+    /**
+     * total weight.
+     * infinity(Double.MAX_VALUE) means unreachable.
+     */
+    private final DoubleValue totalWeight;
+
+    public ShortestPathValue() {
+        this.path = new IdList();
+        this.pathWeight = new ListValue<DoubleValue>();
+        this.totalWeight = new DoubleValue(Double.MAX_VALUE);
+    }
+
+    @Override
+    public void read(RandomAccessInput in) throws IOException {
+        this.path.read(in);
+        this.pathWeight.read(in);
+        this.totalWeight.read(in);
+    }
+
+    @Override
+    public void write(RandomAccessOutput out) throws IOException {
+        this.path.write(out);
+        this.pathWeight.write(out);
+        this.totalWeight.write(out);
+    }
+
+    @Override
+    public List<Object> value() {
+        return this.path.value();
+    }
+
+    public void updatePath(Vertex vertex, double weight) {
+        this.path.add(vertex.id());
+        this.pathWeight.add(new DoubleValue(weight));
+        this.totalWeight.value(this.getTotalWeight());
+    }
+
+    public void updatePath(IdList path, ListValue<DoubleValue> pathWeight, Vertex vertex) {
+        this.path.clear();
+        this.pathWeight.clear();
+
+        this.path.addAll(path.copy().values());
+        this.pathWeight.addAll(pathWeight.copy().values());
+
+        this.path.add(vertex.id());
+        this.totalWeight.value(this.getTotalWeight());
+    }
+
+    public IdList path() {
+        return this.path;
+    }
+
+    public ListValue<DoubleValue> pathWeight() {
+        return this.pathWeight;
+    }
+
+    public double totalWeight() {
+        return this.totalWeight.doubleValue();
+    }
+
+    private double getTotalWeight() {
+        double totalWeight = 0;
+        for (int i = 0; i < this.pathWeight.size(); ++i) {
+            totalWeight += this.pathWeight.get(i).doubleValue();
+        }
+        return totalWeight;
+    }
+}