A difficulty in this simultaneous multiscale optimization approach is that the loss function values for the different target domains might be poorly comparable. For example, the error for the RCE (err RCE ≈ 10% . . . 100%) is approximately one to two orders of magnitude higher than the error for the density (err dens ≈ 0.5% . . . 15%) and while an error of approximately 10% for the RCE is acceptable, it would be too large for the density, rendering the parameter sets unusable for reproducing experimental results.