FFTW preset, how to define fftw_iodim for guru interface?

[hageldave]

Hey, so I' trying to figure out on how to create the iodims parameter for the guru interface planner method:

public static native fftw_plan fftw_plan_guru_split_dft_r2c(
                             int rank, @Const fftw_iodim dims,
			     int howmany_rank,
			     @Const fftw_iodim howmany_dims, double[] in, double[] ro, double[] io,
			     @Cast("unsigned") int flags);

This is the oficial fftw documentation on this method: http://www.fftw.org/fftw3_doc/Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs

So in cpp the dims argument could be generated like so:

std::vector<fftw_iodim> ioDims;
ioDims.push_back({width, 1,1});
ioDims.push_back({height, width, width});
ioDims.push_back({1,width*height, width*height});
fftw_plan p = fftw_plan_guru_split_dft_r2c(
   3, ioDims.data(), 
   0, NULL, 
   realIn, realOut, imagOut
   FFTW_ESTIMATE);

In java however I cannot figure out on how to create the ioDims array due to the crazy pointering.
I've been trying the following (used do_not_use_me because its the only iodim class that lets me set its parameters in an easy way):

fftw_iodim_do_not_use_me d0 = new fftw_iodim_do_not_use_me().n(width).is(1).os(1);
fftw_iodim_do_not_use_me d1 = new fftw_iodim_do_not_use_me().n(height).is(width).os(width);
fftw_iodim_do_not_use_me d2 = new fftw_iodim_do_not_use_me().n(1).is(width*height).os(width*height);
fftw_iodim dims = new fftw_iodim(d0).put(d1).put(d2);

fftw_plan plan = fftw3.fftw_plan_guru_split_dft_r2c(
   3, dims, 
   0, null, 
   inR, outR, outI, 
   (int)fftw3.FFTW_ESTIMATE);

but this gives me fftw: alloc.c:269: assertion failed: p
How am I supposed to do this correctly?

[saudet]

It's just a simple struct: http://www.fftw.org/fftw3_doc/Guru-vector-and-transform-sizes.html Call "array = new fftw_iodim(n)" and "array.position(i)" instead of "fftw_iodim array[n]" and "array[i]", and that's pretty much it. What doesn't work when doing that?

[hageldave]

Thanks for the quick answer.
I'm using the following maven release (which i believe is the latest release, as 3.3.6 is still SNAPSHOT)

<groupId>org.bytedeco.javacpp-presets</groupId>
<artifactId>fftw-platform</artifactId>
<version>3.3.5-1.3</version>

There seems to be no such constructor new fftw_iodim(int n) which would let me specify an array length. The only constructors present are:
new fftw_iodim() and new fftw_iodim(Pointer p).
So do I have to use calloc or realloc to allocate a void* array , put my fftw_iodim in there and then use the pointer cast constructor new fftw_iodim(Pointer p) with that array?

Also, suppose I would not use the fftw_iodim_do_not_use_me class but instead the normal fftw_iodim, how would I set the parameters?

[hageldave]

Alright I figured it out, I guess. It seems like you have to use the fftw_iodim_do_not_use_me class (what exactly does that name imply?) as this class has the array constructor. Also Loader.sizeof(fftw_iodim.class); throws a NullpointerException whereas Loader.sizeof(fftw_iodim_do_not_use_me.class); returns 12 (3*4bytes). So what I ended up doing was
Creating a fftw_iodim_do_not_use_me array, setting its contents using position(long) and put(Pointer) and then using the pointer cast constructor of fftw_iodim(Pointer) with that array.

static void execSplit2D(int width, int height, double[] inR, double[] outR, double[] outI){
	try(
			fftw_iodim_do_not_use_me d0 = new fftw_iodim_do_not_use_me();
			fftw_iodim_do_not_use_me d1 = new fftw_iodim_do_not_use_me();
			fftw_iodim_do_not_use_me d2 = new fftw_iodim_do_not_use_me();
			fftw_iodim_do_not_use_me array = new fftw_iodim_do_not_use_me(3);
			fftw_iodim dims = new fftw_iodim(array);
	){
		d0.n(width).is(1).os(1);
		d1.n(height).is(width).os(width);
		d2.n(1).is(width*height).os(width*height);
		array.position(0).put(d0).position(1).put(d1).position(2).put(d2);
		fftw_plan plan = fftw3.fftw_plan_guru_split_dft_r2c(
				3, dims, 
				0, null, 
				inR, outR, outI, 
				(int)fftw3.FFTW_ESTIMATE);
		fftw3.fftw_execute_split_dft_r2c(plan, inR, outR, outI);
	}
}

[saudet]

I see, the definition of fftw_iodim is missing. We'll need to locate it and add it.

[saudet]

Fixed in the commit above! Thanks for reporting.