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- Pieter Ghysels, Wim Vanroose
- Parallel Computing
- 2014

Scalability of Krylov subspace methods suffers from costly global synchronization steps that arise in dot-products and norm calculations on parallel machines. In this work, a modified Conjugate Gradient (CG) method is presented that removes the costly global synchronization steps from the standard CG algorithm by only performing a single non-blocking… (More)

- Pieter Ghysels, Thomas J. Ashby, Karl Meerbergen, Wim Vanroose
- SIAM J. Scientific Computing
- 2013

In the Generalized Minimal Residual Method (GMRES), the global all-to-all communication required in each iteration for orthogonalization and normalization of the Krylov base vectors is becoming a performance bottleneck on massively parallel machines. Long latencies, system noise and load imbalance cause these global reductions to become very costly global… (More)

- François-Henry Rouet, Xiaoye S. Li, Pieter Ghysels, Artem Napov
- ACM Trans. Math. Softw.
- 2016

In this report, we replicate a subset of the performance results in the article “A distributed-memory package for dense Hierarchically Semi-Separable matrix computations using randomization.”

- Pieter Ghysels, Xiaoye S. Li, François-Henry Rouet, Samuel Williams, Artem Napov
- SIAM J. Scientific Computing
- 2016

We present a sparse linear system solver that is based on a multifrontal variant of Gaussian elimination, and exploits low-rank approximation of the resulting dense frontal matrices. We use hierarchically semiseparable (HSS) matrices, which have low-rank off-diagonal blocks, to approximate the frontal matrices. For HSS matrix construction, a randomized… (More)

Writing well-performing parallel programs is challenging in the multicore processor era. In addition to achieving good per-thread performance, which in itself is a balancing act between instruction-level parallelism, pipeline effects and good memory performance, multi-threaded programs complicate matters even further. These programs require synchronization,… (More)

- Pieter Ghysels, Przemyslaw Klosiewicz, Wim Vanroose
- Numerical Lin. Alg. with Applic.
- 2012

SUMMARY The basic building blocks of a classic multigrid algorithm, which are essentially stencil computations, all have a low ratio of executed floating point operations per byte fetched from memory. This important ratio can be identified as the arithmetic intensity. Applications with a low arithmetic intensity are typically bounded by memory traffic and… (More)

- Thomas J. Ashby, Pieter Ghysels, Wim Heirman, Wim Vanroose
- ICA3PP
- 2012

Krylov Subspace Methods (KSMs) are popular numerical tools for solving large linear systems of equations. We consider their role in solving sparse systems on future massively parallel distributed memory machines, by estimating future performance of their constituent operations. To this end we construct a model that is simple, but which takes topology and… (More)

- Pieter Ghysels, Giovanni Samaey, +9 authors D. Roose
- 2009

We present a multiscale method for the simulation of large viscoelastic deformations and show its applicability to biological tissue such as plant tissue. At the microscopic level we use a particle method to model the geometrical structure and basic properties of individual cells. The cell fluid, modeled as a viscoelastic fluid by means of Smoothed Particle… (More)

- Pieter Ghysels, Wim Vanroose
- SIAM J. Scientific Computing
- 2015

- Pieter Ghysels
- 2013

The basic building blocks of the classic geometric multigrid algorithm are all essentially stencil computations and have a low ratio of executed floating point operations per byte fetched from memory. On modern computer architectures, such computational kernels are typically bounded by memory traffic and achieve only a small percentage of the theoretical… (More)