[GRASSLIST:2454] Re: Grass5pre2. Compilation problem on RedHat 7.1

[Glynn Clements]

Daniel Tourde wrote:

> I will try to recompile with zlib but it seems that I need fftw.h and I
> don't have this file (I have several ones that look like "cousin" of it
> but not fftw.h)
> 
> [root at brest root]# locate fftw.h
> /usr/include/dfftw.h
> /usr/include/drfftw.h
> /usr/include/sfftw.h
> /usr/include/srfftw.h

The following is from the FFTW documentation:

  Installing FFTW in both single and double precision
  
  It is often useful to install both single- and double-precision
  versions of the FFTW libraries on the same machine, and we provide a
  convenient mechanism for achieving this on Unix systems.
  
  When the --enable-type-prefix option of configure is used, the FFTW
  libraries and header files are installed with a prefix of `d' or `s',
  depending upon whether you compiled in double or single precision. 
  Then, instead of linking your program with -lrfftw -lfftw, for
  example, you would link with -ldrfftw -ldfftw to use the
  double-precision version or with -lsrfftw -lsfftw to use the
  single-precision version. Also, you would #include <drfftw.h> or
  <srfftw.h> instead of <rfftw.h>, and so on.
  
  The names of FFTW functions, data types, and constants remain
  unchanged! You still call, for instance, fftw_one and not dfftw_one. 
  Only the names of header files and libraries are modified. One
  consequence of this is that you cannot use both the single- and
  double-precision FFTW libraries in the same program, simultaneously,
  as the function names would conflict.

By default, you only get double-precision (the --enable-float option
gives single precision instead).

I suggest making some symlinks:

	fftw.h		->	dfftw.h
	rfftw.h		->	drfftw.h
	libfftw.a	->	libdfftw.a
	librfftw.a	->	libdrfftw.a

NB: GRASS only uses the complex functions (fftw.h/libfftw.a), not the
real functions (rfftw.h/librfftw.a).

-- 
Glynn Clements <glynn.clements at virgin.net>