fullstack/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/graph/GlobalAggregator.java

package edu.uci.ics.pregelix.api.graph;

import java.io.IOException;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;

import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;

/**
 * This is the abstract class to implement for aggregating the state of all the vertices globally in the graph.
 * </p>
 * The global aggregation of vertices in a distributed cluster include two phase:
 * 1. a local phase which aggregates vertice sent from a single machine and produces
 * the partially aggregated state;
 * 2. a final phase which aggregates all partially aggregated states
 * 
 * @param <I extends Writable> vertex identifier type
 * @param <E extends Writable> vertex value type
 * @param <E extends Writable> edge type
 * @param <M extends Writable> message type
 * @param <P extends Writable>
 *        the type of the partial aggregate state
 * @param <F extends Writable> the type of the final aggregate value
 */

@SuppressWarnings("rawtypes")
public abstract class GlobalAggregator<I extends WritableComparable, V extends Writable, E extends Writable, M extends Writable, P extends Writable, F extends Writable> {
    /**
     * initialize aggregator
     */
    public abstract void init();

    /**
     * step through all vertex at each slave partition
     * 
     * @param vertexIndex
     * @param msg
     * @throws IOException
     */
    public abstract void step(Vertex<I, V, E, M> v) throws HyracksDataException;

    /**
     * step through all intermediate aggregate result
     * 
     * @param partialResult
     *            partial aggregate value
     */
    public abstract void step(P partialResult);

    /**
     * finish partial aggregate
     * 
     * @return the final aggregate value
     */
    public abstract P finishPartial();

    /**
     * finish final aggregate
     * 
     * @return the final aggregate value
     */
    public abstract F finishFinal();
}