Speaker
Description
URL for further information
http://cern.ch/diane ; http://cern.ch/ganga
Keywords
LQCD, theoretical physics, Monte-Carlo simulation, scheduling, resource selection, DIANE, Ganga
Conclusions and Future Work
The first phase of the LQCD Production 2008 is now finished and scientific results published. The application porting methodology proved to be efficient and reliable. It allowed for non-trivial customization of the scheduling and resource selection strategies to respond to the application-specific requirements.
The system is now routinely used by the theoretical physicist who currently aim at increasing the precision of the results obtained in the first phase.
Detailed analysis
The goal of the LQCD simulation is to study the QCD critical point (second-order phase transition of the guark-gluon plasma), which is the object of both experimental and theoretical searches, the former by heavy-ion collision experiments at RHIC (Brookhaven) and soon at LHC, the latter by numerical lattice simulations.
The LQCD analysis workflow involves active participation of the end-users who refine the simulation parameters in response to the intermediate simulation results. This leads to the introduction of different job scheduling
strategies which are automatically applied by the system. The management of the Grid jobs is fully automatized and the system is able to run autonomously for long periods of time, each spanning several weeks. Additionally a resource selection algorithm allows to maximize the system's efficiency.
We discuss the resource allocation and scheduling aspects for the LQCD application on the EGEE Grid.
Impact
What makes the LQCD simulation particularly interesting is that the measured response to an increase in baryon density is opposite in sign to standard expectations. This surprising result is obtained, for now, on a very coarse lattice, and needs to be confirmed on finer ones. If it turns out to be a property of the continuum QCD theory, it will have a profound impact on the QCD phase diagram. In particular, it will make it unlikely to find a QCD critical point at small baryon density. The scientific results were published in the paper "The chiral critical point of Nf = 3 QCD at finite density to the order (mu/T)4" which is available at arxiv repository.
The Lattice QCD Grid Production 2008 is an ideal demonstration of the user-level tools and methodology with the EGEE Grid, providing efficient, reliable and scalable environment for solving complex scientific problems. This approach has significant potential for other applications in EGEE Grid.