ASC/Alliances Center for Astrophysical Thermonuclear Flashes FLASH Capabilities, Architecture, and Future Directions Anshu Dubey, Elias Balarus, Sean Couch, Chris Daley, Shravan Gopal, Carlo Graziani, Don Lamb, Dongwook Lee, Marcos Vanella, , Klaus Weide, Guohua Xia Abstract : FLASH is a highly capable, fully modular, professionally managed code with a wide user base. FLASH consists of inter-operable modules that can be combined to generate different applications such as novae, supernovae, X-Ray bursts, galaxy clusters, weakly compressible turbulence and many other problems in astrophysics and other fields. With its flexibility and extensibility, FLASH provides an excellent foundation for an open software base for other research communities such as the academic HEDP, and CFD/CFM. The HEDP project is underway in-house, with modeling of 2T, and laser energy deposition, while a Fluid Structure Interaction CFM project is being carried out in collaboration with University of Maryland. Additionally there is an NSF funded in-house project to add a fully implicit solver with AMR to enable simulations of phenomena that have a wide dynamic range of timescales. FLASH team is working to enhance the code in several directions simultaneously. We are adding physics solvers to enable simulations in fields that are new to FLASH, such as High Energy Density Physics, and Fluid Structure Interactions. We are also working with architecture, programming models and scientific libraries communities to ensure continued portability and scalability of the code. FLASH Version 3 FLASH is a multi-physics Eulerian code and framework whose capabilities include AMR, solvers for hydro, MHD, gravity, nuclear burning, several other source terms and material properties, Lagrangian tracer and active particles, and a mechanism to handle various types of EOS. It is also very portable, scales up to 160K processors. FLASH is composed of inter-opreable units/modules, particular modules are set up together to run different physics problems. FLASH is professionally managed with regression testing, version control, coding standards, extensive documentation, user support, and an active users list. More than 600 scientists around the world have now used FLASH, and more than 340 papers have been published that report results that directly use it. The last release of versions 3 was on October 20, 2010 FLASH Version 4 The first release of Version 4 expected in April/May 2011. With this release FLASH will exist in two distinct incarnations. One that will continue to be distributed under the current licensing agreement, and will contain all the traditional capabilities, and the capabilities added to support High Energy Density Physics. These capabilities are being added with joint funding from the DOE NNSA and ASCR offices. The second incarnation will be distributed freely from a mirror site at University of Maryland, and will have capabilities for Computational Fluid Dynamics/Mechanics. This set of capabilities is being added under NSF Peta-apps and PIF programs. High-order unsplit Compressible Hydro solver Incompressible Navier-Stokes Solver Fully implicit solvers Second-order (explicit) super- time-stepping for stiff systems Scalable Poisson solver-hybrid of multigrid and parallel exact solver Infrastructure Additional AMR packages such as Chombo and/or SAMRAI Generalization of Lagrangian infrastructure Shared memory infrastructure at wrapper layer Preparing code for multicore/heterogeneous architectures State-of-the-art parallel I/O General Purpose Solvers (all have AMR capabilities) FLASH Community and External Contributions: Plasma particle-in-cell solver : Mats Holmstrom Most recent addition, immediately beneficial for our HEDP efforts Primordial Chemistry: William Gray (being imported) Enhancement to Particles mapping : being added by Milos and Chalence Multigrid : Paul Ricker Navier-Stokes Solver: Marcos Vanella/Elias Balaras Direct gravity solver : Tom Theuns Single source ray trace, Erik Jan Rijkhorst, adapted later by Natalie Hinkel Barnes hut tree solver: Kevin Olson Ionization : Salvatore Orlando Two-temperatures (Te, Ti) hydro with Radiation Embedded boundaries Multi-component EOS with ionization and radiation Lagrangian trackers communicating to and from fluid Ray tracing and laser energy deposition Domain Specific Capabilities HEDP CFD/CFM This work was supported in part at U. Chicago by ASCR, Office of Science, DOE, and ASC, NNSA, DOE, and at U. Chicago and U. Maryland by OCI/NSF