Accelerating Astronomical Source Extraction with Graphics Processors

MPhil Thesis Defence


Title: "Accelerating Astronomical Source Extraction with Graphics 
Processors"

By

Mr. Baoxue ZHAO


Abstract

In astronomical observatory projects, source extraction is the process of 
extracting celestial objects from observational images and outputting 
object catalogs. It is the basis for the various analysis tasks that are 
subsequently performed on the catalog products.  With the rapid progress 
of new, large astronomical projects, observational images will be produced 
every few seconds. This high speed of image production requires fast 
source extraction. Unfortunately, current source extraction tools cannot 
meet the online  processing requirement.

In this thesis work, we propose to use the GPU (Graphics Processing Unit) 
to accelerate source extraction. Specifically, we start from SExtractor, 
an astronomical source extraction tool widely used in astronomy projects, 
and study its parallelization on the GPU. In our GPU-SExtractor, we 
re-design and parallelize the three major steps of SExtractor: 1) 
Background Computation, 2) Multi-Threshold Object Detection and 3) Object 
Analysis. In particular, we identify the Multi-Threshold Object Detection 
step as the most complex and time-consuming, and design a parallel 
detection algorithm based on Connected-Component Labelling. Furthermore, 
we apply compaction techniques to optimize the detection algorithm to 
better utilize the massive GPU thread parallelism. In the Object Analysis 
step, we decompose the analysis into a sequence of GPU-friendly 
data-parallel primitives to compute the attributes of each extracted 
object. We have evaluated our GPU-SExtractor in comparison with the 
original SExtractor on a desktop with an Intel i7 CPU and an NVIDIA GTX670 
GPU on a set of real-world and synthetic astronomical images of different 
sizes. The results show that our GPU-SExtractor outperforms the original 
SExtractor by a factor of 6, taking a merely 1.9 second to process a 
typical 4KX4K image containing 167,000 celestial objects.


Date:			Monday, 15 December 2014

Time:			10:00am - 12:00noon

Venue:			Room 4483
 			Lifts 25/26

Committee Members:	Dr. Qiong Luo (Supervisor)
 			Dr. Pedro Sander (Chairperson)
 			Dr. Huamin Qu


**** ALL are Welcome ****