Dynamical Anisotropic-Clover Lattice Production for Hadronic Physics J. Foley, C. Morningstar, CMU K. Orginos, College W&M J. Dudek, R. Edwards, B. Joo, D. Richards, C. Thomas, JLab S. Wallace, U. of Maryland H.-W. Lin, U. of Washington N. Mathur, Tata Institute M. Peardon, S. Ryan, Trinity College

Anisotropic Lattices for Hadronic Physics Hadronic spectroscopy –Hadron resonance determinations –Exotic meson spectrum and transition form-factors –HadSpec (Richards) Hadronic structure –3-D picture of hadrons from gluon & quark spin+flavor dist. –Ground & excited E&M transition FF-s –E&M polarizabilities of hadrons –FormFactor (Orginos), EMC (Walker-Loud), DISCO (Osborn) Nuclear interactions –Nuclear processes relevant for stellar evolution –Hyperon-hyperon scattering –3 & 4 nucleon interaction properties –NPLQCD (Savage) Physics of BSM –Neutron decay constraints on BSM from Ultra Cold Neutron source (LANL) –FormFactor (Orginos)

Hadronic Spectroscopy New generation of experiments: hadron spectroscopy –GlueX (JLab/HallD) –Panda (GSI/Fair) –BES III (Beijing) Spectrum: (Anisotropic-Clover fermions) –Excited state baryon resonances (Hall B) –Conventional and exotic (hybrid) mesons (Hall D) –Ground and excited state form-factors (Hall B) Critical need: –Hybrid meson spectrum/photo-coupling –Baryon spectrum

N f =2+1 Anisotropic Clover: dynamical generation Current proposal: 32 3 x256 at m ¼ ~ 230 MeV, a s =0.1227fm Two streams: ORNL & ANL 15 M core-hours / 1000 traj. Future INCITE+ESP: 48 3 x256 at m ¼ ~ 140 MeV Blue uses NSF resources

HMC Improvements Recent major improvements/changes: –2-flavor Clover mass preconditioned by TWM –MD integration all in double precision –Switch to “reliable” mixed-precision IBiCG inverter -Threading + QMP -> coalesce communications Current effort: –Implementing force-gradient integrator –Tuning viaShadow Hamiltonian – >~ 2X improvement?

Performance of Cray vs BG/P Cray hour ~ BG/P hour

Performance of Cray vs BG/P Crays: loaded system -> comms interference -> perf. degradation BG/P Crays (loaded)Cray (dedicated)

Current production strategy Two streams of 230 MeV – ORNL+ANL Appear sufficiently decorrelated Expect total of 10k trajectories with 5k in each stream

Priorities Current calculations at m ¼ ~ 230 MeV Finite volume effects: –Crucial for resonance/scattering extraction Chiral effects (large pion mass) appear large –Excited resonance: chiral extrap. problematic High statistics important (~1000 cfgs) Discretization effects (rotational) appear negligible –Evidence via spectra of Subduced operators Priorities: 1.Physical 6fm box -> 48 3 x256 2.Second lattice ~500MeV pion mass

Longer term Unify calculations of spectroscopy & structure Idea outlined at NP Exascale meeting small lattice spacing (< 0.06fm)

Hadron Spectrum: Complete factorization of resource requirements Gauge generation: –INCITE: Crays/BG/P-s, ~ 16K – 24K cores –Double precision with mixed precision solves Valence spectrum: Distillation –Perambulators (~propagators) 1 GPU (24 3 x128) or 8 GPU+IB (32 3 x256) Currently single precision (could be double) –Contractions: Clusters: many cores, 1 time-slice per core Double precision Infiniband only for I/O

Distillation: mesons Smearing in correlator: use low-rank approximation Correlator Factorizes: operators and perambulators A posteriori evaluation of C (2) after ¿ arxiv:

Distillation: annihilation diagrams Two-meson creation op Correlator arxiv:

Perambulators Current calculation (24 3 x128, m ¼ ~ 230MeV) Solve: [all space sites] Perambulator High angular momentum (J = 4), want N = 128 All time-sources -> 64K inversions / config Can construct all possible source/sink multi-particles Ideally suited for GPU-s: –300 configs on 180 GPU-s -> GF/gpu

Care and feeding of GPUs Front-end overhead a BIG concern (Amdahl’s law) Solver (IBiCGstab): 1 GPU ~ 256 7n-cores Front-end memory footprint: 12 GB Time/solve ~ 100 secs Inner-products only over (at most) 8 cores For work on 2 gpus/box (4 cores): lose ~ 10% –Using threading in QDP/C++ with QMT or OpenMP Older cards: no ECC, double precision performance small Mileage will vary for other applications…

Operators and contractions New operator technique: Subduction –Derivative-based continuum ops -> lattice irreps –Operators at rest or in-flight, mesons & baryons Large basis of operators -> lots of contractions –E.g., nucleon H g 49 ops up through 2 derivs Feed all this to variational method –Diagonalization: handles near degeneracies PRL 103 (2009)

Subduced operators: demonstration GPU results in “friendly-user” time: m ¼ ~ 383MeV, 16 3 x128, 479 configs < 2% error bars Spin identified Need multi- hadron ops !!

Prospects Gauge production: –Used by several proposals –ORNL: Run-time environment effects on performance –ANL: welcome “big-job” queues Distillation + subduction –Looks promising! –Framework for multi-particle states –Flexible: useful for 2-pt and 3-pt GPU-s –Powerful resource for inversions –New ECC+double precision -> handle contractions