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Java example source code file (RandomWalker.java)

This example Java source code file (RandomWalker.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

builder, cutoff_on_disconnected, exception_on_disconnected, igraph, noedgehandling, override, padding, padding_on_disconnected, randomwalker, restart_on_disconnected, self_loop_on_disconnected, sequence, unsupportedoperationexception, util, walkdirection

The RandomWalker.java Java example source code

package org.deeplearning4j.models.sequencevectors.graph.walkers.impl;

import lombok.NonNull;
import org.apache.commons.lang3.ArrayUtils;
import org.deeplearning4j.models.sequencevectors.graph.enums.NoEdgeHandling;
import org.deeplearning4j.models.sequencevectors.graph.enums.WalkDirection;
import org.deeplearning4j.models.sequencevectors.graph.exception.NoEdgesException;
import org.deeplearning4j.models.sequencevectors.graph.primitives.IGraph;
import org.deeplearning4j.models.sequencevectors.graph.primitives.Vertex;
import org.deeplearning4j.models.sequencevectors.graph.walkers.GraphWalker;
import org.deeplearning4j.models.sequencevectors.sequence.Sequence;
import org.deeplearning4j.models.sequencevectors.sequence.SequenceElement;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * This is Random-based walker for SequenceVectors-based DeepWalk implementation
 *
 * Original DeepWalk paper: http://arxiv.org/pdf/1403.6652v2
 *
 * @author AlexDBlack
 * @author raver119@gmail.com
 *
 * Based on Alex Black RandomWalkIterator implementation
 */
public class RandomWalker<T extends SequenceElement> implements GraphWalker {
    protected int walkLength = 5;
    protected NoEdgeHandling noEdgeHandling = NoEdgeHandling.EXCEPTION_ON_DISCONNECTED;
    protected IGraph<T, ?> sourceGraph;
    protected AtomicInteger position = new AtomicInteger(0);
    protected Random rng = new Random(System.currentTimeMillis());
    protected long seed;
    protected int[] order;
    protected WalkDirection walkDirection;
    protected double alpha;

    private static final Logger logger = LoggerFactory.getLogger(RandomWalker.class);

    protected RandomWalker() {

    }


    /**
     * This method checks, if walker has any more sequences left in queue
     *
     * @return
     */
    @Override
    public boolean hasNext() {
        return position.get() < sourceGraph.numVertices();
    }

    /**
     * This method returns next walk sequence from this graph
     *
     * @return
     */
    @Override
    public Sequence<T> next() {
        int[] visitedHops = new int[walkLength];
        Arrays.fill(visitedHops, -1);

        Sequence<T> sequence = new Sequence();

        int startPosition = position.getAndIncrement();
        int lastId = -1;
        int startPoint = order[startPosition];
        //System.out.println("");


        startPosition = startPoint;

        //if (startPosition == 0 || startPoint % 1000 == 0)
         //   System.out.println("ATZ Walk: ");

        for (int i = 0; i < walkLength; i++) {
            Vertex<T> vertex = sourceGraph.getVertex(startPosition);

            int currentPosition = startPosition;

            sequence.addElement(vertex.getValue());
            visitedHops[i] = vertex.vertexID();
            //if (startPoint == 0 || startPoint % 1000 == 0)
              // System.out.print("" + vertex.vertexID() + " -> ");


            if (alpha > 0 && lastId != startPoint && lastId != -1 && alpha > rng.nextDouble()) {
                startPosition = startPoint;
                continue;
            }


            // get next vertex
            switch (walkDirection) {
                case RANDOM: {
                        int[] nextHops = sourceGraph.getConnectedVertexIndices(currentPosition);
                        startPosition = nextHops[rng.nextInt(nextHops.length)];
                    };
                    break;
                case FORWARD_ONLY: {
                        // here we remove only last hop
                        int[] nextHops = ArrayUtils.removeElements(sourceGraph.getConnectedVertexIndices(currentPosition), lastId);
                        if (nextHops.length > 0) {
                            startPosition = nextHops[rng.nextInt(nextHops.length)];
                        } else {
                            switch (noEdgeHandling) {
                                case CUTOFF_ON_DISCONNECTED: {
                                        i += walkLength;
                                    }
                                    break;
                                case EXCEPTION_ON_DISCONNECTED: {
                                        throw new NoEdgesException("No more edges at vertex ["+currentPosition +"]");
                                    }
                                case SELF_LOOP_ON_DISCONNECTED: {
                                    startPosition = currentPosition;
                                    }
                                    break;
                                case PADDING_ON_DISCONNECTED: {
                                    throw new UnsupportedOperationException("PADDING not implemented yet");
                                    }
                                case RESTART_ON_DISCONNECTED: {
                                        startPosition = startPoint;
                                    }
                                    break;
                                default:
                                    throw new UnsupportedOperationException("NoEdgeHandling mode ["+noEdgeHandling+"] not implemented yet.");
                            }
                        }
                    };
                    break;
                case FORWARD_UNIQUE: {
                    // here we remove all previously visited hops, and we don't get  back to them ever
                    int[] nextHops = ArrayUtils.removeElements(sourceGraph.getConnectedVertexIndices(currentPosition), visitedHops);
                    if (nextHops.length > 0) {
                        startPosition = nextHops[rng.nextInt(nextHops.length)];
                    } else {
                        // if we don't have any more unique hops within this path - break out.
                        switch (noEdgeHandling) {
                            case CUTOFF_ON_DISCONNECTED: {
                                    i += walkLength;
                                }
                                break;
                            case EXCEPTION_ON_DISCONNECTED: {
                                    throw new NoEdgesException("No more edges at vertex ["+currentPosition +"]");
                                }
                            case SELF_LOOP_ON_DISCONNECTED: {
                                    startPosition = currentPosition;
                                }
                                break;
                            case PADDING_ON_DISCONNECTED: {
                                    throw new UnsupportedOperationException("PADDING not implemented yet");
                                }
                            case RESTART_ON_DISCONNECTED: {
                                    startPosition = startPoint;
                                }
                                break;
                            default:
                                throw new UnsupportedOperationException("NoEdgeHandling mode ["+noEdgeHandling+"] not implemented yet.");
                        }
                    }
                };
                break;
                case FORWARD_PREFERRED: {
                        // here we remove all previously visited hops, and if there's no next unique hop available - we fallback to anything, but the last one
                        int[] nextHops = ArrayUtils.removeElements(sourceGraph.getConnectedVertexIndices(currentPosition), visitedHops);
                        if (nextHops.length == 0) {
                            nextHops = ArrayUtils.removeElements(sourceGraph.getConnectedVertexIndices(currentPosition), lastId);
                            if (nextHops.length == 0) {
                                switch (noEdgeHandling) {
                                    case CUTOFF_ON_DISCONNECTED: {
                                            i += walkLength;
                                        }
                                        break;
                                    case EXCEPTION_ON_DISCONNECTED: {
                                            throw new NoEdgesException("No more edges at vertex ["+currentPosition +"]");
                                        }
                                    case SELF_LOOP_ON_DISCONNECTED: {
                                            startPosition = currentPosition;
                                        }
                                        break;
                                    case PADDING_ON_DISCONNECTED: {
                                            throw new UnsupportedOperationException("PADDING not implemented yet");
                                        }
                                    case RESTART_ON_DISCONNECTED: {
                                            startPosition = startPoint;
                                        }
                                        break;
                                    default:
                                        throw new UnsupportedOperationException("NoEdgeHandling mode ["+noEdgeHandling+"] not implemented yet.");
                                }
                            } else startPosition = nextHops[rng.nextInt(nextHops.length)];
                        }
                    }
                    break;
                default:
                    throw new UnsupportedOperationException("Unknown WalkDirection ["+ walkDirection +"]");
            }

            lastId = vertex.vertexID();
        }

        //if (startPoint == 0 || startPoint % 1000 == 0)
            //System.out.println("");
        return sequence;
    }

    /**
     * This method resets walker
     *
     * @param shuffle if TRUE, order of walks will be shuffled
     */
    @Override
    public void reset(boolean shuffle) {
        this.position.set(0);
        if (shuffle) {
            logger.debug("Calling shuffle() on entries...");
            // https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
            for(int i=order.length-1; i>0; i-- ){
                int j = rng.nextInt(i+1);
                int temp = order[j];
                order[j] = order[i];
                order[i] = temp;
            }
        }
    }

    public static class Builder<T extends SequenceElement> {
        protected int walkLength = 5;
        protected NoEdgeHandling noEdgeHandling = NoEdgeHandling.RESTART_ON_DISCONNECTED;
        protected IGraph<T, ?> sourceGraph;
        protected long seed = 0;
        protected WalkDirection walkDirection = WalkDirection.FORWARD_ONLY;
        protected double alpha;

        /**
         * Builder constructor for RandomWalker
         *
         * @param graph source graph to be used for this walker
         */
        public Builder(@NonNull IGraph<T, ?> graph) {
            this.sourceGraph = graph;
        }

        /**
         * This method specifies output sequence (walk) length
         *
         * @param walkLength
         * @return
         */
        public Builder<T> setWalkLength(int walkLength) {
            this.walkLength = walkLength;
            return this;
        }

        /**
         * This method defines walker behavior when it gets to node which has no next nodes available
         * Default value: RESTART_ON_DISCONNECTED
         *
         * @param handling
         * @return
         */
        public Builder<T> setNoEdgeHandling(@NonNull NoEdgeHandling handling) {
            this.noEdgeHandling = handling;
            return this;
        }

        /**
         * This method specifies random seed.
         *
         * @param seed
         * @return
         */
        public Builder<T> setSeed(long seed) {
            this.seed = seed;
            return this;
        }

        /**
         * This method defines next hop selection within walk
         *
         * @param direction
         * @return
         */
        public Builder<T> setWalkDirection(@NonNull WalkDirection direction) {
            this.walkDirection = direction;
            return this;
        }

        /**
         * This method defines a chance for walk restart
         * Good value would be somewhere between 0.03-0.07
         *
         * @param alpha
         * @return
         */
        public Builder<T> setRestartProbability(double alpha) {
            this.alpha = alpha;
            return this;
        }

        /**
         * This method builds RandomWalker instance
         * @return
         */
        public RandomWalker<T> build() {
            RandomWalker<T> walker = new RandomWalker();
            walker.noEdgeHandling = this.noEdgeHandling;
            walker.sourceGraph = this.sourceGraph;
            walker.walkLength = this.walkLength;
            walker.seed = this.seed;
            walker.walkDirection = this.walkDirection;
            walker.alpha = this.alpha;

            walker.order = new int[sourceGraph.numVertices()];
            for (int i =0; i <walker.order.length; i++) {
                walker.order[i] = i;
            }

            if (this.seed != 0)
                walker.rng = new Random(this.seed);

            return walker;
        }
    }
}

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