docs: public static SparseMatrix random(int[] dim) {
  		Random r = new Random();
  		SparseMatrix matrix = new SparseMatrix(dim);
  		for(int i=0;i<dim[0];i++)
  			for(int j=0;j<dim[1];j++)
  			{
  				int []indices={i,j};
  				matrix.set(indices, r.nextFloat());
  			}
  		return matrix;
  	}