Incremental Compilation Issue

[Altera_Forum]

I am trying to shorten my compilation by using incremental compilation but I don't think it's working. I think it's re-compiling my fft module every time, despite my not making any changes to it. 

 In my design, I am using the FFT v2.1.1 MegaWizard Plug-in. I have figured that this module is probably taking up a lot of the compilation time, and since I never make any change to it, I can speed up the compilation process by setting it as a design partition and using incremental compilation.  I have full incremental compilation turned on, I've set the fft instance as a design partition in the Project Navigator window, and I've set each partition's Netlist Type to Post-Fit. However, the compilation time is not reduced and messages in the processing tab indicate to me that it is re-compiling the fft module. If I don't make any changes to the design, the re-compilation is instantaneous. But if I make a slight change, it re-compiles my whole design. It is as if the incremental compilation is working but the design partitions are being ignored.  I have three design partitions: the whole project, an instance of my design, and the fft instance. The compilation time is about 40 minutes.

[Altera_Forum]

Hi ferus, 

 To find out why partitions aren't being preserved, there are a few report panels to check:  1) The Fitter report includes panels called "Preservation Summary" and "Partition Settings" which breakdown on a per-partition basis how much was preserved. It also shows what the requested netlist-type was for each partition and what was actually used.  2) The Synthesis report includes a panel called "Dependent Source Files" for each partition along with which one it detected as changed. This can help you narrow down why a partition was re-synthesized.