Thanks for the improvement!

Is this pull request related to issue #47 ?

Actually, it is more of a cleanup and an optimization providing a workaround for yet not directly addressing issue #47 and the corresponding discussion.
By applying a simple round of constraint propagation from the sudoku mask, the search space is significantly reduced, allowing for a gain of an order of magnitude without any significant init time impact, but the problem seems to remain that I wasn't able to trigger lateral exploration past 50 generations.
I believe this might be an issue to investigate with the library itself, with Elite selection and Elite reinsertion consistently yielding better results.