Fourier-domain dedispersion

Abstract

We present and implement the concept of the Fourier-domain dedispersion (FDD) algorithm, a brute-force incoherent dedispersion algorithm. This algorithm corrects the frequency-dependent dispersion delays in the arrival time of radio emission from sources such as radio pulsars and fast radio bursts. Where traditional time-domain dedispersion algorithms correct time delays using time shifts, the FDD algorithm performs these shifts by applying phase rotations to the Fourier-transformed time-series data. Incoherent dedispersion to many trial dispersion measures (DMs) is compute-, memory-bandwidth-, and input-output-intensive, and dedispersion algorithms have been implemented on graphics processing units (GPUs) to achieve high computational performance. However, time-domain dedispersion algorithms have low arithmetic intensity and are therefore often memory-bandwidth-limited. The FDD algorithm avoids this limitation and is compute-limited, providing a path to exploit the potential of current and upcoming generations of GPUs. We implement the FDD algorithm as an extension of the DEDISP time-domain dedispersion software. We compare the performance and energy-to-completion of the FDD implementation using an NVIDIA Titan RTX GPU against both the standard version and an optimized version of DEDISP. The optimized implementation already provides a factor of 1.5 to 2 speedup at only 66% of the energy utilization compared to the original algorithm. We find that the FDD algorithm outperforms the optimized time-domain dedispersion algorithm by another 20% in performance and 5% in energy-to-completion when a large number of DMs (≳512) are required. The FDD algorithm provides additional performance improvements for fast-Fourier-transform-based periodicity surveys of radio pulsars, as the Fourier transform back to the time domain can be omitted. We expect that this computational performance gain will further improve in the future since the Fourier-domain dedispersion algorithm better matches the trends in technological advancements of GPU development.