docs: protected void updateMatrix(double[][] mat, final double[] evec, double eval) {
      final int size = mat.length;
      for(int i = 0; i < size; i++) {
        final double[] mati = mat[i];
        final double eveci = evec[i];
        for(int j = 0; j < size; j++) {
          mati[j] -= eval * eveci * evec[j];
        }
      }
    }