I just tagged release 1.7 of dupd.
See the ChangeLog for a list of changes.
The major change is that the SSD mode has been removed. That’s a bit sad because as I’ve written over the years, the SSD mode is/was faster in some scenarios when reading off a SSD. However, as I’ve also mentioned, the drawback was that the SSD mode could be vastly slower in the “wrong” circumstances.
As of version 1.6 I intended to keep both so the best one can be used in each situation. During the 1.7 development I ended up doing internal code refactoring on the HDD mode to make it simpler and faster. The end result was that the two implementations diverged ever further apart to the point that they barely shared any code. And the HDD mode became almost as fast as the SSD mode at its best, although not quite.
Maintaining the two separate code paths was becoming too much of a burden though. Given the nature of a hobby open source project I can only dedicate so much (read: little) time to it so, sadly, the SSD mode is gone. On the positive side, this allowed me to remove a lot of code, which is nice.