ATLAS e-News
23 February 2011
Keeping ahead in the software game
28 November 2007
A simulation of Grid production rate
How does the ATLAS team of software developers ensure that their software, which has been in development for over five years, is optimised for the latest computer hardware?
Through a never-ending schedule of adaptive re-designs, say Dario Barberis of CERN and Genoa Unviersity/INFN, and David Quarrie at the Lawrence Berkeley National Lab, California.
“File transfer time is now independent of file size,” says Dario. “That’s something we didn’t predict even a few years ago.” It takes roughly 40 seconds for the Tier-0 system to establish a secure, encrypted contact with Tier-1 systems, but because bandwidths of 10 Gbit/sec are now available, it takes just a few seconds to actually transfer even the largest data files between systems.
“Just 12 months ago, we imagined small file transfer would be best – small files are fast to send and can be easily handled by a personal computer for analysis,” continues Dario. “But there’s a lot of electronic bookkeeping involved in file transfer.”
Because large bandwidths are now available, file transfer protocols will be restructured to focus on sending fewer, larger files from ATLAS to centres around the world and reducing the quantity of bookkeeping.
With each workshop we find solutions to older problems, but inevitably new ones arise
Recent changes in computer processor design are also having an impact on the ATLAS software systems, says David. “We assumed that processor power would continue to double every 18 months or so.”
In fact, processor power is no longer rising, and there is more emphasis on using multi-core processors to cope with rising power requirements. “To take full advantage of that multi-core technology we need to send multiple datasets through the processors,” David says. “We’re no longer looking at sending a single data stream through ever-faster single chips.”
Dario and David discussed possible solutions to these problems and others at the latest ATLAS Software and Computing Workshop, held at CERN in the final week of October. “With each workshop we find solutions to older problems, but inevitably new ones arise,” says Dario. “We’re still making good progress though.”