Example 2: Fast Fourier Transforms

When calling the detailed complex-to-complex FFT routine, S3L_fft_detailed, you can supply a multidimensional parallel array and specify whether you want to perform a forward transform, an inverse transform, or no transform along each axis. You can also specify axes along which no transform is performed, but address bits are reversed. The axes that are transformed or bit-reversed are the data axes, and define the cell; the axes along which you perform no transformation are the instance axes.

The simple FFT routine, S3L_fft, performs a transform along each axis of the supplied parallel array. Consequently, it does not support multiple instances.