Graphics processing unit-assisted density profile calculations in the KSTAR reflectometera

Wavelet transform (WT) is widely used in signal processing. The frequency modulation reflectometer in the KSTAR applies this technique to get the phase information from the mixer output measurements. Since WT is a time consuming process, it is difficult to calculate the density profile in real time. The data analysis time, however, can be significantly reduced by the use of the Graphics Processing Unit (GPU), with its powerful computing capability, in WT. A bottle neck in the KSTAR data processing exists in the data input and output (IO) process between the CPU and its peripheral devices. In this paper, the details of the WT implementation assisted by a GPU in the KSTAR reflectometer are presented and the consequent performance improvement is reported. The real time density profile calculation from the reflectometer measurements is also discussed.