docs: public static double[] pairwiseMultiply(double[] a, double[] b) {
      if (a.length != b.length) {
        throw new RuntimeException("Can't pairwise multiple different lengths: a.length=" + a.length + " b.length=" + b.length);
      }
      double[] result = new double[a.length];
      for (int i = 0; i < result.length; i++) {
        result[i] = a[i] * b[i];
      }
      return result;
    }