Xolotl: A New Plasma Facing Component Simulator

1. Xolotl: A New Plasma Facing Component Simulator Scott Forest Hull II Jr. Software Developer Oak Ridge National Laboratory hullsf@ornl.gov

2. Project Overview: The overall goal of the project: • Develop and deploy high performance simulations capable of predicting the lifetime and durability of tungsten-based plasma-facing components in a “hot” fusion plasma environment. • Modeling surface morphology evolution in erosion or re-deposition regimes. • Recycling of hydrogenic species. • Xolotl (SHO-lottle) – new code to simulate 3D continuum reaction-diffusion for long-time morphological and chemical evolution.

3. Project Overview (Continued) • This code is being built from scratch! • ORNL tasked with Xolotl Development. • Funded by Fusion Energy Sciences (FES) and Advanced Scientific Computing Research ASCR/SciDAC. • Participants of various institutions and PI, including Oak Ridge National Laboratory (ORNL), Los Alamos National Lab (LANL), Pacific Northwest National Laboratory (PNNL), Argonne National Laboratory (ANL), and others. • Proposal funding is for Fiscal Year 2012-2016.

4. Science Lesson • Develop a new simulator to predict PFC lifetime and performance. • Integrating and applying discrete particle-based, as well as continuum-based, multi-scale modeling techniques to provide scientific discovery of the mechanism controlling PFC and bulk materials evolution under fusion plasma and 14-MeV neutron exposure. • Will work on various HPC machines, including Jaguar/Titan – targeting HPC CPU/GPU hybrids as a main focus. • Solving coupled reaction-diffusion problem.

5. Parallel Programming Model Exact model determined during design phase, but some ideas: • OpenMP, MPI, Pthreads – also investigating OpenACC. • Languages: C++ • Runtime libraries and frameworks include Integrated Plasma Simulator (IPS) and Mesh-Oriented datABase (MOAB). • Parallel build with CMake and Ctest • OpenCL and CUDA – explored for new data structures and reveal tasks within a timestep. • Hybrid MPI + X – expand spatial scales of the problems.

6. Performance and Scaling • Since this is a new project, bottlenecks and scaling can only be predicted. • The programs will scale to a height of the largest available systems on the current and future market. • Collect application-specific data at a relatively coarse-grained level. • Use tools, like HPCToolKit and mpiP, for application analysis.

7. Tools • Debug with logging and GDB. Valgrind as necessary. • VisIt and ParaView for visualization tools. • NEAMS integrated Computational Environment (NiCE) for leveraging an existing system for data and workflow management. • Eclipse IDE, IBM’s Rational Software Architecture (RSA) for programming environment and development. • Development Techniques: • Unified Modeling Language (UML) • Test Driven Development (TDD)

8. Roadmap • Release 1.0 on Sourceforge of Plasma Facing Components (PFC) Code within the first year. • Code Refinement in sequential years for Xolotl: • Xolotl simulations for PFC surface and near surface evaluations. • Xolotl simulations to evaluate bulk neutron-induced defect cluster and gas bubble response. • Work on 10,000 cores by year three.

9. Questions Questions? Email me: hullsf@ornl.gov THANK YOU!