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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code
The extended-MHD NIMROD code [C. R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)] is verified against the ideal-MHD ELITE code [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)] on a diverted tokamak discharge. When the NIMROD model complexity is increased incrementally, resistive and first-order finite-Larmour radius effects are destabilizing and stabilizing, respectively. Lastly, the full result is compared to local analytic calculations which are found to overpredict both the resistive destabilization and drift stabilization in comparison to the NIMROD computations.
Nyx: A MASSIVELY PARALLEL AMR CODE FOR COMPUTATIONAL COSMOLOGY
We present a new N-body and gas dynamics code, called Nyx, for large-scale cosmological simulations. Nyx follows the temporal evolution of a system of discrete dark matter particles gravitationally coupled to an inviscid ideal fluid in an expanding universe. The gas is advanced in an Eulerian framework with block-structured adaptive mesh refinement; a particle-mesh scheme using the same grid hierarchy is used to solve for self-gravity and advance the particles. Computational results demonstrating the validation of Nyx on standard cosmological test problems, and the scaling behavior of Nyx to 50,000 cores, are presented.
Excited-state one-neutron halo nuclei within a parallel momentum distribution analysis
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Sparse Matrix Partitioning for Parallel Eigenanalysis of Large Static and Dynamic Graphs.
Abstract not provided.
Kokkos/Qthreads Task Parallel Approach to Linear Algebra Based Graph Analytics.
Abstract not provided.
Exploration of Fine-Grained Parallelism for Load Balancing Eager K-truss on GPU and CPU.
Abstract not provided.
Parallel, Portable Algorithms for Distance-2 Maximal Independent Set and Graph Coarsening.
Abstract not provided.
Basker: A Threaded Sparse LU Factorization Utilizing Hierarchical Parallelism and Data Layouts.
Abstract not provided.
Tacho: Memory-Scalable Task Parallel Sparse Cholesky Factorization.
Abstract not provided.
Optimizing Multi-Image Sort-Last Parallel Rendering
Abstract not provided
Implementation of Temporal Parallelization for Rapid Quasi-Static Time-Series (QSTS) Simulations.
Abstract not provided.
Highly parallel scanning tunneling microscope based hydrogen depassivation lithography
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Toward an Evolutionary Task Parallel Integrated MPI + X Programming Model.
Abstract not provided.
Moment representation in the lattice Boltzmann method on massively parallel hardware
The widely-used lattice Boltzmann method (LBM) for computational fluid dynamics is highly scalable, but also significantly memory bandwidth-bound on current architectures. This paper presents a new regularized LBM implementation that reduces the memory footprint by only storing macroscopic, moment-based data. We show that the amount of data that must be stored in memory during a simulation is reduced by up to 47%. We also present a technique for cache-aware data re-utilization and show that optimizing cache utilization to limit data motion results in a similar improvement in time to solution. These new algorithms are implemented in the hemodynamics solver HARVEY and demonstrated using both idealized and realistic biological geometries. We develop a performance model for the moment representation algorithm and evaluate the performance on Summit.