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Commit 4a762c74 authored by Matthieu Schaller's avatar Matthieu Schaller
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Added slides for the last three main SWIFT talks.

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1 merge request!8Added slides for the last three main SWIFT talks.
...@@ -4,6 +4,44 @@ ...@@ -4,6 +4,44 @@
# references. Nominally we will use /talks. # references. Nominally we will use /talks.
cards: cards:
- meeting: Supercomputing Frontiers Europe 2018
location: Warsaw, Poland
date: March 2018
title: "Individual time-stepping in cosmological simulations: A challenge for strong scaling and domain decomposition algorithms"
author: Matthieu Schaller
abstract: "For many decades cosmological simulations have used individual time-steps for the particles (or cells) that are evolved forward in time. Given the large range in time-step sizes
required for accurate integration, this allows substantial gains in time to solution compared to the more widely adopted in science technique of using a single time-step for the whole
computational domain. However, only limited work has been done to improve domain decomposition techniques to make them aware of this multiple time-stepping scheme. This results in domains
perfectly suited for time-steps where most particles require updating but leads to terrible performance with large levels of imbalance for the steps where only a small fraction of particles are
being updated. This generates poor overall strong-scaling performance and leads to a poor utilisation of the systems.
In this paper, we will introduce some of these short-comings and present a solution based on task-based parallelism and a weighted graph domain decomposition algorithm implemented in the
open-source cosmological code SWIFT. By carefully weighting the different tasks in an overall cluster-wide graph, we can divide the work and not the data optimally. If we further penalise the
creation of communication tasks we can achieve a domain decomposition where no MPI communication is required for the time-steps with few active particles. This effectively eliminates most imbalance
issues and leads to optimal performance not just for time-steps with large number of updates but also for the ones with few particles to update. We achieve much better strong-scaling performance than
commonly used codes and achieve a time-to-solution 30 times smaller than the de-facto standard Gadget code."
links:
- href: "SuperComputingFrontiers_2018.pdf"
name: Slides
- meeting: SIAM Conference on Parallel Procecssing for Scientific Computing 2018
location: Tokyo, Japan
date: March 2018
title: "Using Task-Based Parallelism, Asynchronous MPI and Dynamic Workload-Based Domain Decomposition to Achieve Near-Perfect Load-Balancing for Particle-Based Hydrodynamics and Gravity"
author: Matthieu Schaller
links:
- href: "SIAM_2018.pdf"
name: Slides
- meeting: Intel HPC DevCon 2017
location: Denver, USA
date: November 2017
title: "Task-based Calculation + Task-based MPI + Task-based I/O = Maximal Performance"
author: Matthieu Schaller
links:
- href: "HPC_DevCon_2017.pdf"
name: Slides
- meeting: ParCo Conference 2017 - meeting: ParCo Conference 2017
location: Bologna, Italy location: Bologna, Italy
date: September 2017 date: September 2017
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