FFTW3 file referenced in a FFTW2 compilation

[robmost]

Hi,

I want to compile genetIC with FFTW2 support. Following the documentation, I commented the FFTW3 flags and instead turned on the FFTW2 ones:

FFTW    = -DFFTW_TYPE_PREFIX=1
FFTWLIB = -ldfftw -ldrfftw

but at compilation time I get

In file included from src/ic.hpp:16:0,
                 from src/main.cpp:9:
src/tools/numerics/fourier.hpp:6:10: fatal error: fftw3.h: No such file or directory
 #include <fftw3.h>
          ^~~~~~~~~
compilation terminated.
make: *** [src/main.o] Error 1

It seems that fourier.hpp, which is included in main.cpp through ic.hpp, calls fftw3.h even with the FFTW2 flags on. Is there something else I am not configuring properly?

[apontzen]

Oh dear! It's a long time since this has been tested. Is there a particular reason you want to do this?

[robmost]

The GADGET3 version I'm using only supports FFTW2 and I wanted to keep everything in my pipeline within the same environment. It's not a big deal, I can change to FFTW3 when generating the ICs, I was just wondering if it was an issue on my end.

[apontzen]

Not likely to be a problem on your end. The code isn’t regularly tested against FFTW2 so probably at some point an error has slipped in where it still tries to include FFTW3 headers. You could try editing out those FFTW3 headers manually to see whether it fixes it. We can add FFTW2 to the CI matrix if this is important, it’s just an oversight that I think we had all forgotten about it…

[robmost]

We can add FFTW2 to the CI matrix if this is important, it’s just an oversight that I think we had all forgotten about it…

No worries!
I tried the straightforward solution and added a conditional compilation flag in fourier.hpp:

#ifdef FFTW3
#include <fftw3.h>
#endif

but it wasn't as easy as that 😄

For the time being, I can stick to FTTW3 and focus on other issues. If it's OK with you, maybe we keep this issue open so the rest of the users are aware of it?

[apontzen]

Looking at this, I think it's been too long since we used FFTW2 and it would be significant work to reintroduce and test it. Thanks for spotting it, though, I'll update the documentation to remove any reference to being able to work with FFTW2.