/*
* 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.giraph.examples.scc;
import it.unimi.dsi.fastutil.longs.LongArrayList;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.Writable;
/**
* Vertex value for the Strongly Connected Components algorithm. It keeps track
* of the parents of the vertex in order to traverse the graph backwards.
*/
public class SccVertexValue implements Writable {
/** Vertex's parents **/
private LongArrayList parents;
/** Current vertex value **/
private long value = Long.MIN_VALUE;
/** Indicates whether the vertex was trimmed, hence,
* it can't be part of the computation anymore.
*/
private boolean active = true;
/**
* Public constructor required for serialization.
*/
public SccVertexValue() {
}
/**
* Constructor
* @param value Initial value for this vertex.
*/
public SccVertexValue(long value) {
this.value = value;
}
@Override
public void readFields(DataInput in) throws IOException {
value = in.readLong();
int size = in.readInt();
if (size != 0) {
for (int i = 0; i < size; i++) {
addParent(in.readLong());
}
}
active = in.readBoolean();
}
@Override
public void write(DataOutput out) throws IOException {
out.writeLong(value);
int size = parents == null ? 0 : parents.size();
out.writeInt(size);
if (size != 0) {
for (long incomingId : parents) {
out.writeLong(incomingId);
}
}
out.writeBoolean(active);
}
/**
* Returns the list of parent vertices, i.e., vertices that are at the other
* end of incoming edges. If the vertex doesn't have any incoming edge, it
* returns null.
* @return List of the vertex's parents.
*/
public LongArrayList getParents() {
return parents;
}
/**
* Adds a vertex id to the list of parent vertices.
* @param vertexId It of the parent vertex.
*/
public void addParent(long vertexId) {
// Initialize the list of parent vertices only when one attempts to add
// the first item, so we save some memory on vertices that have no incoming
// edges
if (parents == null) {
parents = new LongArrayList();
}
parents.add(vertexId);
}
/**
* Clear parents list.
*/
public void clearParents() {
parents = null;
}
/**
* Sets the vertex value. At the end of the SCC computation, vertices with the
* same vertex value are part of the same component.
* @param value Vertex value.
*/
public void set(long value) {
this.value = value;
}
/**
* Returns the vertex value. At the end of the SCC computation, vertices with
* the same vertex value are part of the same component.
* @return Current vertex value.
*/
public long get() {
return value;
}
/**
* Remove this vertex from the computation.
*/
public void deactivate() {
this.active = false;
}
/**
* Indicates whether the vertex was removed in a Trimming phase.
* @return True if the vertex was trimmed, otherwise, return false.
*/
public boolean isActive() {
return active;
}
@Override
public String toString() {
return String.valueOf(value);
}
}