Qdp++ and Chroma Robert Edwards

QDP++ and Chroma

• Robert Edwards

• Jefferson Lab

• http://www.lqcd.org

• http://www.jlab.org/~edwards/qdp

• http://www.jlab.org/~edwards/chroma

QDP++ Optimization

• Optimizations “under the hood”

• Select numerically intensive operations through template specialization.
• PETE recognises expression templates like:
• z = a * x + y
• from type information at compile time.
• Calls machine specific optimised routine (axpyz)
• Optimized routine can use assembler, reorganize loops etc.
• Optimized routines can be selected at configuration time,
• Unoptimized fallback routines exist for portability

Chroma: A lattice QCD Library using QDP++ and QMP. Work in development

• A lattice QCD toolkit/library built on top of QDP++

• Library is a module – can be linked with other codes.

• Features:

• Utility libraries (gluonic measure, smearing, etc.)
• Fermion support (DWF, Overlap, Wilson, Asqtad)
• Applications
• Spectroscopy, Props & 3-pt funcs, eigenvalues
• Not finished – heatbath, HMC
• Optimization hooks – level 3 Wilson-Dslash for Pentium and now QCDOC

• Large commitment from UKQCD!

Performance Test Case - Wilson Conjugate Gradient

QCDOC Performance Benchmarks

Pentium over Myrinet/GigE Performance Benchmarks

QDP++ Status

• Version 1

• Scalar and parallel versions
• Optimizations for P4 clusters, QCDOC
• Used in production of propagators now at JLab
• QIO (File I/O) with XML manipulation
• Supports both switch and grid-based machines today
• Tested on QCDOC, default version on gigE and switches
• Adopted by and support from UKQCD
• Single out thanks to Balint Joo and Peter Boyle for their outstanding contributions
• High efficiency achievable on QCDOC

Future Work

• QMP

• Further QMP/GigE perf. improvements.

• QDP++

• Generalize comm. structure to parallel transporters – allows multi-dir. shifts.
• Continue leverage off optimized routines
• Increase extent of optimizations for new physics apps

• IO

• Move to new Metadata Standard for gauge configs
• On-going infrastructure devel. for cataloguing/delivery

• Chroma

• Finish HMC implementations for various fermion actions (UKQCD - overlap)