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

2Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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.

3Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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

4Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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.

5Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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.

6Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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.

7Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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)

8Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 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.

9Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Questions Questions? me: THANK YOU!