For the physics software development group at CERN, our second year of Google Summer of Code couldn’t have come at a better time. Motivated by CernVM's awesome experience in 2011, our colleagues from the Geant4 and ROOT software projects joined us as mentors this summer. And while physicists around the world snatched the first evidence of a long-sought Higgs boson from the Large Hadron Collider (LHC), our seven Google Summer of Code students worked on core parts of the open source software engine that makes LHC data processing possible.

Two of our students worked with the Geant4 team at CERN. Geant4 is a toolkit for the simulation of the response of a material when high-energetic particles are passing through it. Geant4 can be used to model a gas detector, a gamma-ray telescope, an electronic device next to an accelerator or the inside of a satellite. In order to keep up with the rate of real data coming from the LHC detectors, Geant4 has to be both accurate and fast.  

• Stathis Kamperis improved the speed of Geant4 by re-ordering the simulation of particles according to particle type. By simulating, for instance, first all electrons, than all photons, and so on, the number of instruction cache misses decreases. In the course of this work, Stathis also ported Geant4 to Solaris which gives us access to the very powerful DTrace profiling machinery.
• Dhruva Tirumala Bukkapatnam contemplated Geant4 pointers and data structures. He developed code for a particle navigation algorithm optimized for use on GPU architectures.

Two more students were working together with the ROOT team. The ROOT framework is the main working horse for LHC experiments to store, analyze, and visualize their data.  

• Omar Zapata Mesa worked on an MPI interface for ROOT. On a cluster of machines, the MPI interface enables ROOT to toss around its C++ objects from node to node while also integrating with ROOT's C++ interpreter.
• Eamon Ford worked on the CERN iOS App.The App brings CERN news and information on an iPad or iPhone. In case you can’t sleep at night, you can now peek at the live display of particle collisions from inside the LHC.

For the CernVM base technology, we had three more students working with us this summer. CernVM provides a virtual appliance used to develop and run LHC data processing applications on the distributed and heterogeneous computing infrastructure that is provided by hundreds of physics institutes and research labs around the world.  

• Josip Lisec, back for his second Google Summer of Code, worked on the log analysis and visualization of CernVM Co-Pilot, the job distribution system which powers the LHC\@home Test4Theory volunteer computing project. Want to see the world map of active volunteers from the 19th of November at 3:07pm?  Check out the Co-Pilot dashboard.
• Francesco Ruvolo worked on broken network services, such as misconfigured DNS or HTTP servers. Breaking such services in a controlled way comes in handy when simulating the behavior of a CernVM running on a hotel WiFi.
• Rachee Singh programmed maintenance tools for the content distribution network that is used by the CernVM File System to distribute terabytes of experiment software to all the worker nodes. All the proxy servers of the content distribution network can now be plotted on a map and every CernVM can automatically find a close proxy by means of a Voronoi diagram produced by Rachee's code.

Overall, we were very glad to see so much interest and enthusiasm from the student programmers in LHC software tools. We’d like to congratulate all of our students on their hard work and on successfully completing the program!

Sun, 09/30/2012 - 00:00 By Jakob Blomer, CERN Organization Administrator (original article on Google Open Source Blog)

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