MatrixAddFunction implements
   MapFunction<Tuple2<Tuple2<Integer, DenseMatrix>, Tuple2<Integer, DenseMatrix>>, Tuple2<Integer, DenseMatrix>> {
   @Override
   public Tuple2<Integer, DenseMatrix> map( Tuple2<Tuple2<Integer, DenseMatrix>, Tuple2<Integer, DenseMatrix>> tuple2Tuple2Tuple2) throws Exception {
      Integer index = tuple2Tuple2Tuple2.f0.f0
      int m = tuple2Tuple2Tuple2.f0.f1.numRows();
      int n = tuple2Tuple2Tuple2.f0.f1.numCols();
      double[] array1 = tuple2Tuple2Tuple2.f0.f1.toArray;
      double[] array2 = tuple2Tuple2Tuple2.f1.f1.toArray();
      ...