docs: @Override
    public void firstPassE(NumberVector vec, double wei) {
      final int dim = mean.length;
      assert (vec.getDimensionality() == dim);
      assert (wei >= 0 && wei < Double.POSITIVE_INFINITY) : wei;
      if(wei < Double.MIN_NORMAL) {
        return;
      }
      // Aggregate
      for(int i = 0; i < dim; i++) {
        mean[i] += vec.doubleValue(i) * wei;
      }
      wsum += wei;
    }