docs: public double[][] getL() {
      double[][] L = new double[m][n];
      L[0][0] = 1.;
      for(int i = 1; i < m; i++) {
        final double[] Li = L[i];
        System.arraycopy(LU[i], 0, Li, 0, Math.min(i, n));
        if (i < n) {
          Li[i] = 1.;
        }
      }
      return L;
    }