Question. I recently ran a job with the available boards as 2440 x 1220 and 3660 x 1220 and the optimiser produced a result using 5 of 1 board and 10 of the other. As an experiment I repeated the run but only made the 3660 x 1220 board available and to my surprise the overall cost was lower! Why does the optimiser not always choose this result even when it is offered a mixture of board sizes?
Answer. Because optimisation is a complex problem if you offer a wider choice of boards you are forcing the optimiser to consider more options. As computing time is limited this means that it does not have so much time to consider the 3660 x 1220 options. This does occasionally produce results like those you describe. It is always difficult to assess the optimiser on a single run because an unexpected result is often caused by a particularly awkward combination of boards or parts. Taken over a reasonable number of runs the optimisers usually do find the best combination of boards.
