The Xidian_unlocked.fet is the original data that can be successfully scheduled by FET, but when I locked the results obtained by scheduling the Xidian_unlocked.fet i.e. generating the Xidian_locked_all.fet, then when I use FET to schedule the Xidian_locked_all.fet again, it would report Impossible.
I thought if I locked all the activities in a timetable (feasible), it will generate the same timetable.
It seems meaningless doing this, but I am curious about the reason why FET would report Impossible in this case.
I think I have found the answer!
I made a mistake.
The activities that should start at the same time were locked at different times.
Sorry about that!