The gravitational billion body problem : Het miljard deeltjes probleem

The increased availability of accelerator technology in modern supercomputers forces users to redesign their algorithms. These accelerators are specifically designed to offer huge amounts of parallel compute power. In this thesis I show how to harness the power of these parallel processors for astrophysical simulations. I start with an introduction that presents the developments in astrophysical algorithms and used hardware since the 1960__s till today. In the following scientific chapters I discuss the use of GPU accelerator technology for direct N-body methods and for the more advanced hierarchical algorithms. These advanced algorithms are more complex to implement on large parallel architectures, but by redesigning the algorithms it is possible to take advantage of the GPU. The developed algorithms are applied to simulate galaxy mergers to explain discrepancies in observational results. In the simulations we test different merger configurations and try to match the results with observational data. The final chapter shows how to scale the developed software code to thousands of GPUs as available in the Titan supercomputer. The in this thesis developed and presented algorithms allow astronomers to take advantage of the new GPU technology and thereby run simulations that contain thousand times more particles than was possible beforeNWOUBL - phd migration 201

A distributed SIRT implementation for the ASTRA Toolbox

The ASTRA Toolbox is a software toolbox that enables rapid development of GPU accelerated tomography algorithms. It contains GPU implementations of forward and backprojection operations for common scanning geometries, as well as a set of algorithms for iterative reconstruction. These algorithms are currently limited to using a single GPU. A drawback of iterative reconstruction algorithms is that they are slow compared to classical backprojection algorithms. As a result, using only a single GPU can result in prohibitively long reconstruction times when working with large data volumes. In this paper, we present an extension of the ASTRA Toolbox with implementations of forward projection, backprojection and the SIRT algorithm that can be distributed over multiple GPUs and multiple workstations to make processing larger data sets with ASTRA feasible

A distributed ASTRA toolbox

While iterative reconstruction algorithms for tomography have several advantages compared to standard backprojection methods, the adoption of such algorithms in large-scale imaging facilities is still limited,

A distributed ASTRA toolbox

Computational astrophysicsNumber theory, Algebra and Geometr

Modelling the Milky Way as a dry Galaxy

GalaxiesComputational astrophysic

A pilgrimage to gravity on GPUs

In this short review we present the developments over the last 5 decades that have led to the use of Graphics Processing Units (GPUs) for astrophysical simulations. Since the introduction of NVIDIA's Compute Unified Device Architecture (CUDA) in 2007 the GPU has become a valuable tool for N-body simulations and is so popular these days that almost all papers about high precision N-body simulations use methods that are accelerated by GPUs. With the GPU hardware becoming more advanced and being used for more advanced algorithms like gravitational tree-codes we see a bright future for GPU like hardware in computational astrophysics.Comment: To appear in: European Physical Journal "Special Topics" : "Computer Simulations on Graphics Processing Units" . 18 pages, 8 figure

Impact of bar resonances in the velocity-space distribution of the solar neighbourhood stars in a self-consistent N-body galactic disc simulation

Computational astrophysic

Resolving local and global kinematic signatures of satellite mergers with billion particle simulations

Large scale structure and cosmolog

Creating the Virtual Universe

Computational astrophysic