Abstract If Optuna’s built-in NSGAII has a study obtained from another sampler, but continues with that study, it cannot be used as the first generation, and optimization starts from zero. This means that even if you already know good individuals, you cannot use it in the GA.
In this implementation, the already sampled results are included in the initial individuals of the GA to perform the optimization.
Note, however, that this has the effect that the implementation does not necessarily support multi-threading in the generation of the initial generation.