by Boonyarit Changaival. Published: 15 September 2014

My work as a summer student focused on implementing and benchmarking the cluster finding algorithm on GPU using C and CUDA library. GPU is known for its overwhelming number of processing cores. Though those cores are not powerful compared to a typical CPU, due to the large number used the task can be broken down into small pieces and processed concurrently. The performance gain is distinctively high in various kinds of task such as matrix manipulation. With a given format of data and the algorithm function, GPU seemed to be a very good platform since the algorithm can be derived into a very fine grain level, possibly one thread for one hit on the chip because of its massive amount of processing cores. For example, in GTX780, there are 2304 cuda cores comparing to i7 with just 4 cores (but, of course, more powerful). In addition, GPU was shown to be very efficient with another cluster finding algorithm for ALICE TPC detector.

The algorithm is separated in 6 small functions (or kernels) to group all adjacent hits on the same chip together. Then, the centre of gravity of each group or cluster is calculated to represent all hits in the cluster. Achieving the high throughput is not trivial. Several optimizations were done such as Zero Copy, Non-blocking transfer of data, parameters tuning and pipelining which helped to improve performance by a factor of 4.

Boonyarit Changaival (Bird) and Sarunya Pumma, 2014 CERN summer students from Thailand in front of the Globe.

My work here was really interesting but life at CERN has more to offer. I love meeting new people and traveling. My favourite trip was in Zermatt and Interlaken with my colleague Kwang, and my supervisor, Tiranee, and other Thais. Those two places were so beautiful and I would love to come back someday. I made a lot of friends here as well. Most of them are summer students, though. Their stories were so fascinating. Even if I have not yet traveled to their countries, their stories already took me there. With the social network being easily accessed, I believe we can always be in touch.

I was also able to visit all 4 detectors; ATLAS, ALICE, CMS and LHCb. It was such a great experience. I also presented my work at the poster session on 6th August. It was nice to see people interested in your work and willing to learn more and profit from your project. All in all, my experience here at CERN exceeded my expectations by far and I could not ask for more!

If you ask me what I will remember about my time at CERN, it will have to be all the stories I heard at the lunch table, the laughs I shared with others and the fun trips and visits. Without them, this wouldn’t have been the great experience that it was. I would like to thank Pierre Vande Vyvre and Sylvain Chapeland for all their help. Without them, my experience here might not be what it turned out to be. To all people I did not mention and CERN, you have my gratitude as well. Until we meet again...


Sarunya Pumma

I'm Kwang, CERN summer student from Thailand. I am a computer engineer, so Physics is obviously not an area that I am really interested in. However, working at CERN was a great honour for me. I would say it was one in a lifetime chance. I have always loved to broaden my points of view through reading. During the high school years I started reading English novels and came across Dan Brown’s books.  I remember being so fascinated about stories and in particular about the concept of project collaborations that could run across the globe. 

That was the first time that I knew CERN.  Since then, I have been following the news about CERN and frequently visited the official website. When I got the acceptance letter from CERN, I was so excited! I worked for the ALICE experiment under the project called ‘ALICE O2’. My colleagues in the ALICE experiment were nice, and they were professionals. Being a part of the actual and professional research team drove me to work hard.

Another thing that I loved about CERN was the nationality diversity. I met a lot of people from many different countries around the world, France, Germany, Austria, the US, China, Indonesia, Switzerland and many others. This allowed me to broaden my horizons and greatly amplify my experience. Lastly, I believe that research is the core power that drives the world’s technology, and I have gained valuable experience and skills associated with research unique to CERN. In a few months, I will continue my Ph.D. in the US at Virginia Tech. I am certain that the experience and knowledge that I obtained from CERN will greatly benefit my research in the future.