A QCD Grid: 5 Easy Pieces? Richard Kenway University of Edinburgh

Aug 2001A QCD Grid: 5 Easy Pieces2 the problem of quark confinement quarks come in six flavoursquarks 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 2001A QCD Grid: 5 Easy Pieces3 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 power a L need c 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 2001A QCD Grid: 5 Easy Pieces4 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 QCD configurations

Aug 2001A QCD Grid: 5 Easy Pieces5 5 easy pieces(?) 1data provenance label configurations by physics parameters and history planning to write data in XML format 2data 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 3application 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 2001A QCD Grid: 5 Easy Pieces6 5 easy pieces(?) 4QCD 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 5computation 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 risk insufficient human resources are available to UKQCD today, but the opportunity exists