The mapper of forward propagation part in deep learning MapReduce program

/*
 * Project Name: Deep learning based on Hadoop (MapReduce)
 * 
 * Class Description: 
 * 	This is the mapper of forward propagation part in deep learning MapReduce program.
 *  The task of this MapReduce is to compute the input of next layer using the input 
 *  from lower layer and the weights just computed. 
 *  
 *  It is executed between every two layers. So the total execution time for this MapReduce
 *  program is the number of layers - 1.
 * 
 * Class Structure: 
 * 	It contains four parts: 
 * 		configure() reads all the configurations and distributed cache from outside. 
 * 		initialize() parse the input strings into parameters, and initialize parameters for algorithm.
 * 		prop2nextLayer() compute the forward propagation algorithm.
 * 		map() implements the mapper. It outputs the original key and updated value pair.
 * 
 * Author: Kairan Sun
 * Last Update Date: Nov. 30, 2013 
 */