code: public static final DoubleMatrix1D diagonalMatrixMult(DoubleMatrix1D diagonalM, DoubleMatrix1D vector){
  		int n = diagonalM.size();
  		DoubleMatrix1D ret = DoubleFactory1D.dense.make(n);
  		for(int i=0; i<n; i++){
  			ret.setQuick(i, diagonalM.getQuick(i) * vector.getQuick(i));
  		}
  		return ret;
  	}
docs: Matrix-vector multiplication with diagonal matrix.
  @param diagonalM diagonal matrix M, in the form of a vector of its diagonal elements
  @param vector
  @return M.x