Programming the Cell Processor: For Games, Graphics, and Computation

Appendix C. The Accelerated Library Framework (ALF)

When IBM released version 2.1 of the Cell SDK, I took a long, hard look at the code for the 16M fast Fourier transform (FFT). I’m usually pretty good at deciphering FFTs, but this code was horrendous. It wasn’t the bit reversal or butterfly equations; the problem was data storage and communication. Each FFT stage transferred data with a bewildering series of noncontiguous list operations and stored the data in multiple buffers. I drew diagrams and flowcharts, but the code was so hard to follow that I gave up.

When SDK 3.0 arrived, everything became clear. The algorithm hadn’t changed, but the FFT code had been rewritten using the Accelerated Library Framework (ALF). Thanks to this new structure, ...