The e-Science Institute Dr Anna Kenway, Deputy Director September 2005.
A QCD Grid: 5 Easy Pieces? Richard Kenway University of Edinburgh.
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Transcript of A QCD Grid: 5 Easy Pieces? Richard Kenway University of Edinburgh.
A QCD Grid: 5 Easy Pieces?
Richard KenwayUniversity of Edinburgh
Aug 2001 A QCD Grid: 5 Easy Pieces 2
the problem of quark confinement
• quarks come in six flavours • quarks are confined by the strong force (QCD) into bound states called hadrons
• we cannot directly measure the decay of one quark flavour into another– which may conceal clues to why matter dominates antimatter
• we need reliable simulations of the strong forces between the quarks in a hadron– to infer quark properties from hadron properties
Aug 2001 A QCD Grid: 5 Easy Pieces 3
lattice QCD• quantum mechanics + special relativity
– probabilities from averaging over many realisations– treat space and time on an equal footing hypercubic lattice
• performance number of processors
• lattice spacing must be extrapolated to zero keeping the box large enough– halving the lattice spacing
500 times more computer powera
L
• need c. 1000 teraflops years• QCDOC
– UK-US project– ASIC = PowerPC + 1 Gflops
FPU + 4 MB + 12 links– 5 Tflops / $1 per sustained
Mflops by end 2002– SciDAC funding for software
Aug 2001 A QCD Grid: 5 Easy Pieces 4
why build a QCD grid?
• the computational problem is too big for current computers– configuration generation is tightly coupled a few petaflops
machines, not metacomputing (yet)– post-processing is highly diverse and distributed
• it involves multinational collaborations – (overlapping) virtual organisations are well established and growing
• many terabytes of data should be federated– validity + security are essential, so data provenance is a vital issue
• extensive software exists and should be more widely exploited– must be correct, portable and efficient
QCDconfigurations
2
experiment
ubV
Aug 2001 A QCD Grid: 5 Easy Pieces 5
5 easy pieces(?)
1 data provenance• label configurations by physics parameters and history• planning to write data in XML format
2 data grid• federate global data with open + restricted access via physics
parameters• have translation codes: UKQCD Columbia MILC NERSC• planning data mirroring/caching across TByte RAID disk farms at
Glasgow, Edinburgh, Liverpool and Swansea• possibly extending to US and Germany
3 application code library• validate and maintain an open-source + restricted code base• UKQCD + Columbia are building a CVS repository• other US groups will contribute/exploit open-source codes
(SciDAC)
UKQCD objective: grid functionality, conforming to standards (eg GLOBUS, SRB) by exploiting leverage with other projects
Aug 2001 A QCD Grid: 5 Easy Pieces 6
5 easy pieces(?)4 QCD portal
• provide a high-level interface to codes, data and machines• considering a web form to write job scripts, construct I/O files,
submit and monitor jobs, and archive data• also to construct data analysis codes from library routines
5 computation grid• controlled access to global computers + charging mechanism• computational steering for unexplored parameter regions• a long way off!• farming post-processing jobs across UKQCD sites is a feasible
starting point
a QCD grid requires similar functionality to other grids (eg LHC, virtual observatory) but is on a more manageable scale and is
low riskinsufficient human resources are available to UKQCD today, but
the opportunity exists