Xolotl: A New Plasma Facing Component Simulator

Scott Forest Hull IIJr. Software Developer

Oak Ridge National Laboratoryhullsf@ornl.gov

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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.

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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.

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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.

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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.

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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.

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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)

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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.

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Questions

Questions? Email me: hullsf@ornl.gov

THANK YOU!