Dear Don, At the June 28th Allocations Committee meeting, the committee considered your previous request (and other people's requests) in light of available resources in the fourth quarter and they added 125,000 hours. Regards, Ray On 6/30/11 11:48 AM, "[email protected]" <[email protected]> wrote:

Hello,

A change in allocation has been requested:

Requester: sinclair (Donald Sinclair) Project: Lattice-QCD Title: Lattice simulations of Conformal and Walking Technicolor. Description: We perform simulations to evaluate the functional integrals of QCD-like theories formulated on a discrete space-time lattice to enable determination of the non-perturbative aspects these theories. These include the properties of these theories at non-zero temperature including the scales of confinement and chiral symmetry breaking, and such zero temperature properties as spectra, decay constants and the running of the gauge coupling constant. We are particularly interested in those theories where the coupling constant evolves particularly slowly, since these are candidate 'Walking Technicolor' theories. Related to these are theories with an infrared fixed point. Of special interest is to differentiate these two different types of behaviour.

We are performing simulations of QCD-like theories which are models for Walking or Conformal Technicolor. We have been studying theories which are essentially QCD but with colour-sextet rather than colour-triplet quarks. We hope to measure the running of the QCD coupling constant. For 2 or 3 flavours, 2-loop perturbation theory predicts an infrared fixed point. For 2 flavours, it is possible that a chiral condensate forms before this fixed point is reached. If so the fixed point is avoided, the theory is confining and chiral symmetry breaks spontaneously. However, there is a region where the coupling constant evolves very slowly. These are the properties required for a walking technicolor theory. Simulations we have performed so far at finite temperature suggest that this theory does indeed walk. This is an ongoing program at NERSC. We wish to run small-lattice simulations of the 3-flavour theory, which we expect to have conformal, rather than walking behaviour on Fusion, for comparison. If we are correct, the properties of the 2 and 3 flavour theories should look rather different.

Our sextet quark codes are based on our earlier triplet quark codes and use the RHMC simulation method. The Rational Hybrid Monte Carlo (RHMC) is a stochastic molecular dynamics algorithm. The functional integral of QCD is written as a partition function of a classical field theory evolving in a fictitious time. The determinant of the Dirac operator raised to a fractional power is calculated by introducing bosonic fields (pseudofermions), and sandwiching this Dirac operator raised to minus said fractional power between them. This fractional power of the Dirac operator is approximated to machine accuracy by a rational approximation. After defining this this theory on a discrete space-time lattice, the inversions required by the partial-fraction expansion of the rational approximation are performed using Krylov space methods, in particular a multi-shift extension of the conjugate gradient algorithm. A global Metropolis Monte-Carlo accept/reject step applied at the end of each t rajectory removes discretization errors introduced by the numerical integration of these stochastic equations of motion. We parallelize the code by assigning a fixed number of adjacent lattice sites to each MPI task. Network bandwidth ultimately limits how small a chunk of the lattice can be assigned to each task.

Benchmarks of this code on Fusion for the 24^3*12 lattice planned for some of our FY2011 runs give: 24 cores = 46 Gflops 48 cores = 95 Gflops 72 cores = 148 Gflops 96 cores = 220 Gflops 144 cores = 369 Gflops 288 cores = 784 Gflops We plan to run the 24^3*12 lattice jobs on 288 cores (36 nodes). Our smaller lattice 16^3*8 runs would be run on 128 cores (16 nodes).

Current: undetermined amount Justification: This allocation request is based on having one 288 core job or two 128 core jobs running at all times. Our project is expected to use time at NERSC and NICS as well. LCRC has the advantage that it provides facilities for jobs which have medium levels of parallelism such as the 128 and 288 core jobs indicated here, which are discriminated against on larger machines such as Franklin and Hopper(stage 2) at NERSC, and Kraken at NICS. Carver at NERSC provides a similar platform to Fusion, but the large number of users and potential users mean that we cannot rely on it to provide the bulk of our computing at NERSC. Numbers given in the description section indicate that scaling is excellent. We have plans to increase the level of parallelism for this code, but this is probably irrelevant to our Fusion use. For codes which have smaller portions of the lattice on each core, such as our 16^3*8 code, performances of around 3 Gflop/core are sustained.

Requested: 500000

A specific reason has been given: To complete 24^3*8 lattice runs at m=0.0025, beta=6.7, needed to determine if runs on 16^3*8 lattice suffer from finite volume effects. Current allocation is exhausted.

This needs to be approved and the final allocation amount decided upon.

Thank You, The LCRC Accounts System _______________________________________________ allocations-admins mailing list [email protected] https://lists.lcrc.anl.gov/mailman/listinfo/allocations-admins

----------------------------------------- Ray Bair Computing, Environment, and Life Sciences Argonne National Laboratory and the University of Chicago TCS Building 240, Room 4126 9700 South Cass Avenue Argonne, IL 60439 email: rbair(at)anl.gov Phone: (630)252-5751