Dynamically generating FFT code on mobile devices

This paper characterizes the benefits of dynamic code generation when computing the discrete Fourier transform (DFT) on mobile devices. A library called FFTS has recently been shown to be faster than FFTW, Intel IPP and Apple vDSP, partly due to the use of program specialization and dynamic code generation. However, dynamic code generation is prohibited on some mobile platforms for security reasons. In this work, FFTS was modified to avoid dynamic code generation, while making every effort to maximize performance, and the results of benchmarks on Apple A4, A6, Nvidia Tegra3 and Samsung Exynos4 based devices show that disabling dynamic code generation in FFTS decreases performance by as much as 25%, depending on the device and the parameters of the transform.