History of SixTrack in LHC@home

It is worth noting that at the beginning LHC@home and SixTrack were almost one single entity. SixTrack was the first and only application running on the system for quite some time.

In 2003, Eric McIntosh and Andreas Wagner of CERN’s IT Department started testing an in-house screensaver called the Compact Physics Screen Saver (CPSS), which runs SixTrack on desktop computers at CERN. CPSS has proved to be a vital tool for debugging this kind of distributed computing application. A major problem for CPSS and LHC@home was that different PC processors return different results and that, in particular, the elementary mathematical functions such as exponential and logarithm. Eric McIntosh solved this problem with the help of Florent Denichin of ENS Lyon.

In January of 2004, Ben Segal and François Grey of the IT Department were asked to plan an outreach event for CERN’s 50th anniversary that would allow people around the world to get an impression of the computational challenges facing the LHC. Ben and François got in touch with Dave Anderson, the Director of http://setiweb.ssl.berkeley.edu/, who was just beginning to test the new BOINC platform his team had developed. At the same time, a couple of Danish students got in touch with François, eager to find an exciting project for their Masters thesis. This was the beginning of LHC@home. Christian Søttrup and Jakob Pedersen worked furiously all spring and summer to get SixTrack and BOINC to function together. You can read their thesis , which describes the opportunities for combining public resource computing, such as LHC@home, with Grid computing like the LHC Computing Grid.


Some of the people behind screensaver computing at CERN. From left to
right, Frank Schmidt (CERN BE Dept.), Jukka Klem (Helsinki Institute of Physics),
Andreas Wagner (CERN IT Dept.), Eric McIntosh (Former CERN IT Dept. and current BE Dept. honorary member) and Ben Segal (CERN IT Dept.).


Over the summer 2004, a student from Berkeley, Karl Chen, who had been working with Dave Anderson, came over to help Christian and Jacob with the BOINC interface. Jasenko Zivanov, a summer student from Basel University, developed the screensaver graphics. Kalle Happonen and Markku Degerholm, two Finnish students from the Helsinki Institute of Physics technology programme, took turns to set-up and help manage the BOINC server, as the LHC@home team went from alpha-phase, with 25 in-house computers, to beta-phase, with some experienced BOINC users, and finally live in September, just in time for CERN’s 50th anniversary on September 29th, and the CERN openday that followed on October 16th, where over 30,000 people visited CERN. During those months, the user base grew to 6000, which was judged to be the maximum one could cope with given server limitations and the challenge of actually analyzing all the data coming back.

In February 2005, after a break of a few months, LHC@home was restarted as a mainstream service of the CERN IT Department, and as part of the Year of Physics events. Ignacio Reguero managed the project. Together with Phil Defert and Ben Segal he looked into possible new applications with other partners in the High Energy Physics community. They also supervised ‘openlab’ summer students who worked on virtualization techniques to simplify porting of projects and integration with Grid computing (the latter in collaboration with the EGEE project technical director, Erwin Laure). The students were, in chronological order: Morten Siebuhr, Helen McGlone, Louise Oakes, Daniel Alvarez Gomez, Tim Hartnack. Eric McIntosh and Frank Schmidt have continued to work hard to supply data to users of LHC@home, and analyze the results. An important addition to this collaboration is Werner Herr, another accelerator phyisicst at CERN, who has become a big user of Sixtrack on LHC@home. Dobrin Kaltchev at TRIUMF in Canada is also a key player, organizing the submission of jobs to LHC@home for the CERN-based accelerator physicists. Christian Soettrup worked at CERN to help manage the LHC@home server and message boards for much of 2005 and early 2006, and he continues to help from his new position at Niels Bohr Institute, Copenhagen University Faculty of Science. Jukka Klem of the Helsinki Institute of Physics technology programme at CERN is supporting the project, and has helped to ensure that several papers were published concerning the results.

In November 2006 a suggestion to move the LHC@home server and operations out of CERN was being considered. Thanks to the efforts of Sarah Pearce of GridPP in the UK, Queen Mary, University of London, was chosen as a suitable base for the project. Alex Owen and Neasan O'Neill at Queen Mary were the new administrators and preparations were made to hand over to them and move the service to London in early 2007. After months of getting to know the system and buying new kit the 1st of  June 2007 was the first official day of LHC@home running from London and in July of 2007 the website got a makeover.

At that time, other applications came to light and started testing phase on LHC@home and SixTrack was not the one and only application running on the system, even if it remained the only one in full production phase.

Since the move the project has been kept busy crunching plenty of SixTrack work units for the scientists and Massimo Giovannozzi and his team at CERN have continued using it in order to simulate the performance of the LHC machine as constructed in view of predicting its performance before the beam commissioning, which took place on the 10th of September 2008.

Since then, the decision was taken to repatriate the system to CERN, which happened in August 2011 with the help of IT experts and Igor Zacharov from EPFL in view of the future challenges ahead of us. Nowadays, the LHC is producing handful of events each day, and the machine performance should be compared with the results of old and new numerical simulations: all this needs CPU-power! More than this, in spite of the impressive performance of the LHC machine the physicists need even more. It is in the plans of CERN to study an upgrade of the LHC aiming at increasing the machine performance by a factor of ten! This will keep accelerator physicists at CERN busy for some years to come in order to pursue new simulations to study the stability of protons in the upgraded LHC. This will be an ideal challenge for the physicists and volunteers of the SixTrack project within the LHC@home!