Description

A call to S3L_fft_setup is the first step in executing Sun S3L Fast Fourier Transforms. You supply it with the parallel array (a) that is to be transformed. It returns a setup value in setup_id, which you use in subsequent calls to other S3L FFT routines.

When calling S3L_fft_setup, you may supply arbitrary values in a; the setup routine neither examines nor modifies the contents of this parallel array. It simply uses its size and type to create the setup object.

The setup ID computed by the S3L_fft_setup call can be used for any parallel arrays that have the same rank, extents, and type as the a argument supplied in the S3L_fft_setup call--but only for such parallel arrays. If a transform is to be performed on two parallel arrays, a and b, identical in rank, extents, and type, then one call to the setup routine suffices, even if transforms are performed on different axes of the two parallel arrays. But if a and b differ in rank, extents, or type, a separate setup call is required for each.

You may have more than one setup ID active at a time; that is, you may call the setup routine more than once before deallocating any setup IDs. For this reason, be careful that you specify the correct setup ID for calls to S3L_fft, S3L_ifft, S3L_fft_detailed, and S3L_fft_free_setup.

The time required to compute the contents of an FFT setup_id structure is substantially longer than the time required to actually perform an FFT. For this reason, and because it is common to perform FFTs on many parallel variables with the same rank, extents, and type, Sun S3L keeps the setup phase and transform phases distinct.

When a is no longer needed, call S3L_fft_free_setup to deallocate the FFT setup_id.