stream.io.multi.RandomMultiStream Maven / Gradle / Ivy

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package stream.io.multi;

import java.util.Map;

import stream.Data;
import stream.io.DataStream;

public class RandomMultiStream extends AbstractMultiDataStream {

	Double[] weights;


	public Double[] getWeights() {
		return weights;
	}


	public void setWeights(Double[] weights) {
		this.weights = weights;
	}


	@Override
	public void init() throws Exception {
		super.init();

		if( weights == null ){
			log.warn( "No weights specified, using unified distribution over all streams." );
			weights = new Double[ this.additionOrder.size() ];
			for( int i = 0; i < weights.length; i++ ){
				weights[i] = 1.0d / additionOrder.size();
			}
		} else {
			double totalWeight = 0.0d;
			for( int i = 0; i < weights.length; i++ ){
				totalWeight += weights[i];
			}

			for( int i = 0; i < weights.length; i++ ){
				weights[i] = weights[i] / totalWeight;
			}
		}
	}
	
	
	protected String selectNextStream(){
		double rnd = Math.random();
		
		double sum = 0.0d;
		
		for( int i = 0; i < weights.length; i++ ){
			
			if( rnd >= sum && rnd < ( sum + weights[i] ) ){
				return additionOrder.get(i);
			}
			
			sum += weights[i];
		}
		
		return additionOrder.get( additionOrder.size() - 1 );
	}


	@Override
	protected Data readNext(Data item, Map streams) throws Exception {
		String nextKey = selectNextStream(); 
		DataStream stream = streams.get( nextKey );
		Data nextItem = stream.readNext( item );
		nextItem.put( "@stream:id", nextKey );
		return nextItem;
	}
}