Outputs (75)

SYCL compute kernels for ExaHyPE (2024)
Presentation / Conference Contribution

We discuss three SYCL realisations of a simple Finite Volume scheme over multiple Cartesian patches. The realisation flavours differ in the way how they map the compute steps onto loops and tasks: We compare an implementation that is exclusively usin... Read More about SYCL compute kernels for ExaHyPE.

Detrimental task execution patterns in mainstream OpenMP runtimes (2024)
Presentation / Conference Contribution

The OpenMP API offers both task-based and data-parallel concepts to scientific computing. While it provides descriptive and prescriptive annotations, it is in many places deliberately unspecific how to implement its annotations. As the predomina... Read More about Detrimental task execution patterns in mainstream OpenMP runtimes.

Compiler support for semi-manual AoS-to-SoA conversions with data views (2024)
Presentation / Conference Contribution

The C programming language and its cousins such as C++ stipulate the static storage of sets of structured data: Developers have to commit to one, invariant data model -- typically a structure-of-arrays (SoA) or an array-of-structs (AoS) -- unles... Read More about Compiler support for semi-manual AoS-to-SoA conversions with data views.

A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image (2024)
Presentation / Conference Contribution

We produce thickness and bone to soft tissue ratio estimations from a single, 2D medical X-ray image. For this, we simulate the scattering of the rays through a model of the object and embed this simulation into an optimiser which iteratively adjusts... Read More about A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image.

Efficient GPU Offloading with OpenMP for a Hyperbolic Finite Volume Solver on Dynamically Adaptive Meshes (2023)
Presentation / Conference Contribution

We identify and show how to overcome an OpenMP bottleneck in the administration of GPU memory. It arises for a wave equation solver on dynamically adaptive block-structured Cartesian meshes, which keeps all CPU threads busy and allows all of them to... Read More about Efficient GPU Offloading with OpenMP for a Hyperbolic Finite Volume Solver on Dynamically Adaptive Meshes.

Upscaling ExaHyPE – on each and every core (2023)
Report

We study a MPI+multithreaded PDE solver for hyperbolic partial differential equations. Each thread per rank handles a subdomain of the computational domain identified by a segment of a space-filling curve. The threads spawn additional tasks which sho... Read More about Upscaling ExaHyPE – on each and every core.

A multiresolution Discrete Element Method for triangulated objects with implicit time stepping (2022)
Journal Article

Simulations of many rigid bodies colliding with each other sometimes yield particularly interesting results if the colliding objects differ significantly in size and are nonspherical. The most expensive part within such a simulation code is the colli... Read More about A multiresolution Discrete Element Method for triangulated objects with implicit time stepping.

Spherical accretion of collisional gas in modified gravity I: self-similar solutions and a new cosmological hydrodynamical code (2022)
Journal Article

The spherical collapse scenario has great importance in cosmology since it captures several crucial aspects of structure formation. The presence of self-similar solutions in the Einstein-de Sitter (EdS) model greatly simplifies its analysis, making i... Read More about Spherical accretion of collisional gas in modified gravity I: self-similar solutions and a new cosmological hydrodynamical code.

Dynamic task fusion for a block-structured finite volume solver over a dynamically adaptive mesh with local time stepping (2022)
Book Chapter

Load balancing of generic wave equation solvers over dynamically adaptive meshes with local time stepping is dicult, as the load changes with every time step. Task-based programming promises to mitigate the load balancing problem. We study a Finite V... Read More about Dynamic task fusion for a block-structured finite volume solver over a dynamically adaptive mesh with local time stepping.

Principles of Parallel Scientific Computing (2022)
Book

Doubt and Redundancy Kill Soft Errors---Towards Detection and Correction of Silent Data Corruption in Task-based Numerical Software (2021)
Presentation / Conference Contribution

Resilient algorithms in high-performance computing are subject to rigorous non-functional constraints. Resiliency must not increase the runtime, memory footprint or I/O demands too significantly. We propose a task-based soft error detection scheme th... Read More about Doubt and Redundancy Kill Soft Errors---Towards Detection and Correction of Silent Data Corruption in Task-based Numerical Software.

Task inefficiency patterns for a wave equation solver (2021)
Presentation / Conference Contribution

Stabilized Asynchronous Fast Adaptive Composite Multigrid using Additive Damping (2020)
Journal Article

Multigrid solvers face multiple challenges on parallel computers. Two fundamental ones read as follows: Multiplicative solvers issue coarse grid solves which exhibit low concurrency and many multigrid implementations suffer from an expensive coarse g... Read More about Stabilized Asynchronous Fast Adaptive Composite Multigrid using Additive Damping.

Delayed approximate matrix assembly in multigrid with dynamic precisions (2020)
Journal Article

The accurate assembly of the system matrix is an important step in any code that solves partial differential equations on a mesh. We either explicitly set up a matrix, or we work in a matrix‐free environment where we have to be able to quickly return... Read More about Delayed approximate matrix assembly in multigrid with dynamic precisions.

Lightweight Task Offloading Exploiting MPI Wait Times for Parallel Adaptive Mesh Refinement (2020)
Journal Article

Balancing the workload of sophisticated simulations is inherently difficult, since we have to balance both computational workload and memory footprint over meshes that can change any time or yield unpredictable cost per mesh entity, while modern supe... Read More about Lightweight Task Offloading Exploiting MPI Wait Times for Parallel Adaptive Mesh Refinement.

teaMPI---replication-based resiliency without the (performance) pain (2020)
Presentation / Conference Contribution

In an era where we can not afford to checkpoint frequently, replication is a generic way forward to construct numerical simulations that can continue to run even if hardware parts fail. Yet, replication often is not employed on larger scales, as naïv... Read More about teaMPI---replication-based resiliency without the (performance) pain.

Enclave Tasking for DG Methods on Dynamically Adaptive Meshes (2020)
Journal Article

High-order discontinuous Galerkin (DG) methods promise to be an excellent discretization paradigm for hyperbolic differential equation solvers running on supercomputers, since they combine high arithmetic intensity with localized data access, since t... Read More about Enclave Tasking for DG Methods on Dynamically Adaptive Meshes.

ExaHyPE: An engine for parallel dynamically adaptive simulations of wave problems (2020)
Journal Article

ExaHyPE (“An Exascale Hyperbolic PDE Engine”) is a software engine for solving systems of first-order hyperbolic partial differential equations (PDEs). Hyperbolic PDEs are typically derived from the conservation laws of physics and are useful in a wi... Read More about ExaHyPE: An engine for parallel dynamically adaptive simulations of wave problems.

Lazy Stencil Integration in multigrid algorithms (2019)
Presentation / Conference Contribution

The Peano software---parallel, automaton-based, dynamically adaptive grid traversals (2019)
Journal Article

We discuss the design decisions, design alternatives, and rationale behind the third generation of Peano, a framework for dynamically adaptive Cartesian meshes derived from spacetrees. Peano ties the mesh traversal to the mesh storage and supports on... Read More about The Peano software---parallel, automaton-based, dynamically adaptive grid traversals.

Studies on the energy and deep memory behaviour of a cache-oblivious, task-based hyperbolic PDE solver (2019)
Journal Article

We study the performance behaviour of a seismic simulation using the ExaHyPE engine with a specific focus on memory characteristics and energy needs. ExaHyPE combines dynamically adaptive mesh refinement (AMR) with ADER-DG. It is parallelized using t... Read More about Studies on the energy and deep memory behaviour of a cache-oblivious, task-based hyperbolic PDE solver.

A simple diffuse interface approach on adaptive Cartesian grids for the linear elastic wave equations with complex topography (2019)
Journal Article

In most classical approaches of computational geophysics for seismic wave propagation problems, complex surface topography is either accounted for by boundary-fitted unstructured meshes, or, where possible, by mapping the complex computational domain... Read More about A simple diffuse interface approach on adaptive Cartesian grids for the linear elastic wave equations with complex topography.

Efficient Implementation of ADER Discontinuous Galerkin Schemes for a Scalable Hyperbolic PDE Engine (2018)
Journal Article

In this paper we discuss a new and very efficient implementation of high order accurate arbitrary high order schemes using derivatives discontinuous Galerkin (ADER-DG) finite element schemes on modern massively parallel supercomputers. The numerical... Read More about Efficient Implementation of ADER Discontinuous Galerkin Schemes for a Scalable Hyperbolic PDE Engine.

Simulation of tsunamis with the exascale hyperbolic PDE engine ExaHyPE (2018)
Presentation / Conference Contribution

A Multi-Core Ready Discrete Element Method With Triangles Using Dynamically Adaptive Multiscale Grids (2018)
Journal Article

The simulation of vast numbers of rigid bodies of non‐analytical shapes and of tremendously different sizes that collide with each other is computationally challenging. A bottleneck is the identification of all particle contact points per time step.... Read More about A Multi-Core Ready Discrete Element Method With Triangles Using Dynamically Adaptive Multiscale Grids.

HPC Coding: The Power of L(o)osing Control (2018)
Other

Fast DEM collision checks on multicore nodes (2018)
Presentation / Conference Contribution

Many particle simulations today rely on spherical or analytical particle shape descriptions. They find non-spherical, triangulated particle models computationally infeasible due to expensive collision detections. We propose a hybrid collision detecti... Read More about Fast DEM collision checks on multicore nodes.

An experience report on (auto-)tuning of mesh-based PDE solvers on shared memory systems (2018)
Presentation / Conference Contribution

With the advent of manycore systems, shared memory parallelisation has gained importance in high performance computing. Once a code is decomposed into tasks or parallel regions, it becomes crucial to identify reasonable grain sizes, i.e. minimum prob... Read More about An experience report on (auto-)tuning of mesh-based PDE solvers on shared memory systems.

Quasi-matrix-free hybrid multigrid on dynamically adaptive Cartesian grids (2018)
Journal Article

We present a family of spacetree-based multigrid realizations using the tree’s multiscale nature to derive coarse grids. They align with matrix-free geometric multigrid solvers as they never assemble the system matrices, which is cumbersome for dynam... Read More about Quasi-matrix-free hybrid multigrid on dynamically adaptive Cartesian grids.

A Case Study for a New Invasive Extension of Intel's Threading Building Blocks (2018)
Presentation / Conference Contribution

We study codes deploying multiple MPI ranks to one node where each rank is parallelised with TBB. A static assignment of cores to ranks here is disadvantageous if the load is not perfectly balanced, the runtime is subject to fluctuations or one MPI r... Read More about A Case Study for a New Invasive Extension of Intel's Threading Building Blocks.

Complex additive geometric multilevel solvers for Helmholtz equations on spacetrees (2017)
Journal Article

We introduce a family of implementations of low-order, additive, geometric multilevel solvers for systems of Helmholtz equations arising from Schrödinger equations. Both grid spacing and arithmetics may comprise complex numbers, and we thus can apply... Read More about Complex additive geometric multilevel solvers for Helmholtz equations on spacetrees.

Form Follows Function - Do algorithms and applications challenge or drag behind the hardware evolution? (2016)
Presentation / Conference Contribution

Exascale roadmaps are dominated by predictions on hardware trends. At the same time, hardware-software co-design is a frequently cited phrase. It suggests that software development has an impact on the hardware evolution. Is this assumption valid? If... Read More about Form Follows Function - Do algorithms and applications challenge or drag behind the hardware evolution?.

Multiscale Storage, Parallelisation and Programming Paradigms for Spacetrees in Scientific Computing (2016)
Book

More than ten years ago, the Gordon Bell Prize was awarded for a seismic calibration code [2]. According to the authors, mesh generation based upon octrees was one key feature to achieve the reported performance. Octrees look back on a long tradition... Read More about Multiscale Storage, Parallelisation and Programming Paradigms for Spacetrees in Scientific Computing.

On-the-fly memory compression for multibody algorithms (2016)
Presentation / Conference Contribution

Memory and bandwidth demands challenge developers of particle-based codes that have to scale on new architectures, as the growth of concurrency outperforms improvements in memory access facilities, as the memory per core tends to stagnate, and as com... Read More about On-the-fly memory compression for multibody algorithms.

A Contact Detection Code using Triangles for Non-Spherical Particle Simulations (2016)
Presentation / Conference Contribution

We present a novel DEM (discrete element method) code with explicit time stepping. DEM codes simulate billions of small particles that interact with each other primarily through collisions. Different to state-of-the-art codes, we rely on triangulated... Read More about A Contact Detection Code using Triangles for Non-Spherical Particle Simulations.

Two Particle-in-Grid Realisations on Spacetrees (2016)
Journal Article

The present paper studies two particle management strategies for dynamically adaptive Cartesian grids at hands of a particle-in-cell code. One holds the particles within the grid cells, the other within the grid vertices. The fundamental challenge fo... Read More about Two Particle-in-Grid Realisations on Spacetrees.

Integration of FULLSWOF2D and PeanoClaw: Adaptivity and Local Time-stepping for Complex Overland Flows (2015)
Presentation / Conference Contribution

We propose to couple our adaptive mesh refinement software PeanoClaw with existing solvers for complex overland flows that are tailored to regular Cartesian meshes. This allows us to augment them with spatial adaptivity and local time-stepping withou... Read More about Integration of FULLSWOF2D and PeanoClaw: Adaptivity and Local Time-stepping for Complex Overland Flows.

Cache-Oblivious Spacetree Traversals (2015)
Book Chapter

In scientific computing and related fields, mathematical functions are often approximated on meshes where each mesh cell contains a local approximation (e.g., using polynomials) of the represented quantity (density functions, physical quantities such... Read More about Cache-Oblivious Spacetree Traversals.

Adaptivity - and Regular Cartesian Patches for the Shallow Water Equations and Vectorisation of an Augmented Riemann Solver for the Shallow Water Equations (2014)
Presentation / Conference Contribution

PaTriG – Particle Transport Simulation in Grids (2014)
Book Chapter

Block Fusion on Dynamically Adaptive Spacetree Grids for Shallow Water Waves (2014)
Journal Article

Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Even though they directly yield a mesh, it is often computationally reasonable to embed regular Cartesian blocks into their leaves. This promotes stencils working on... Read More about Block Fusion on Dynamically Adaptive Spacetree Grids for Shallow Water Waves.

Hardware-aware block size tailoring on adaptive spacetree grids for shallow water waves (2014)
Presentation / Conference Contribution

Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Though they directly yield an adaptive spatial discretisation, i.e. a mesh, it is often more efficient to augment them by regular Cartesian blocks embedded into the... Read More about Hardware-aware block size tailoring on adaptive spacetree grids for shallow water waves.

PRACE DECI (Distributed European Computing Initiative) Minisymposium (2013)
Presentation / Conference Contribution

Advanced Computing (2013)
Presentation / Conference Contribution

Cluster Optimization and Parallelization of Simulations with Dynamically Adaptive Grids (2013)
Presentation / Conference Contribution

A Case Study on Multi-Component Multi-Cluster Interaction with an AMR Solver (2013)
Presentation / Conference Contribution

SFC-based Communication Metadata Encoding for Adaptive Mesh (2013)
Presentation / Conference Contribution

PeanoClaw - A Functionally-Decomposed Approach to Adaptive Mesh Refinement with Local Time Stepping for Hyperbolic Conservation Law Solvers (2013)
Report

A Toolkit for the Code Development in Advanced Computing (2013)
Report

Autotuning of Adaptive Mesh Refinement PDE Solvers on Shared Memory Architectures (2012)
Presentation / Conference Contribution

Query-driven Parallel Exploration of Large Datasets (2012)
Presentation / Conference Contribution

A Geometric Space-time Multigrid Algorithm for the Heat Equation (2012)
Journal Article

A Coupled Approach for Fluid Dynamic Problems Using the PDE Framework Peano (2012)
Journal Article

A Multiscale Approach for Particle Transport Simulation in Low Reynolds Number Flows (2012)
Report

Peano - A Traversal and Storage Scheme for Octree-Like Adaptive Cartesian Multiscale Grids (2011)
Journal Article

Query-driven Multiscale Data Postprocessing in Computational Fluid Dynamics (2011)
Presentation / Conference Contribution

Argument Controlled Context Profiling (2010)
Presentation / Conference Contribution

A Blocking Strategy on Multicore Architectures for Dynamically Adaptive PDE Solvers (2010)
Presentation / Conference Contribution

An Efficient Parallel Implementation of the MSPAI Preconditioner (2010)
Journal Article

The PDE framework Peano applied to fluid dynamics: an efficient implementation of a parallel multiscale fluid dynamics solver on octree-like adaptive Cartesian grids (2010)
Journal Article

A Precompiler to Reduce the Memory Footprint of Multiscale PDE Solvers in C++ (2010)
Journal Article

A Framework for Parallel PDE Solvers on Multiscale Adaptive Cartesian Grids (2009)
Book

A Coupling Tool for the Partitioned Simulation of Fluid-Structure Interactions (2009)
Presentation / Conference Contribution

Concepts for Efficient Flow Solvers Based on Adaptive Cartesian Grids (2008)
Presentation / Conference Contribution

Concepts for the Efficient Implementation of Domain Decomposition Approaches for Fluid-Structure Interactions (2008)
Presentation / Conference Contribution

Numerical Simulation of Particle Transport in a Drift Ratchet (2008)
Journal Article

A Modular and Efficient Simulation Environment for Fluid-Structure Interactions with Large Domain Deformation (2008)
Presentation / Conference Contribution

DaStGen - A Data Structure Generator for Parallel C++ HPC Software (2008)
Presentation / Conference Contribution

Benefits of Structured Cartesian Gris for the Simulation of Fluid-Structure Interactions (2007)
Presentation / Conference Contribution

A coupling environment for fluid-structure interactions on Cartesian grids (2007)
Presentation / Conference Contribution

A cache-oblivious self-adaptive full multigrid method (2006)
Journal Article

A Parallel Adaptive Cartesian PDE Solver Using Space-Filling Curves (2006)
Presentation / Conference Contribution

Eine cache-optimale Implementierung eines Navier-Stokes Lösers unter besonderer Berücksichtigung physikalischer Erhaltungssätze (2005)
Thesis

SkvG: Cache-Optimal Parallel Solution of PDEs on High Performance Computers Using Space-Trees and Space-Filling Curves (2005)
Presentation / Conference Contribution

Ein Maple-Java-Compiler für eine objektorientierte Maple-Erweiterung (2003)
Thesis