From: Timo Heister Date: Mon, 1 Jun 2020 16:08:19 +0000 (-0400) Subject: add a section about large scale Stokes X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b9c1fbaaa645bfc1bc37e8356d1cf3f0e7edd458;p=release-papers.git add a section about large scale Stokes --- diff --git a/9.2/paper.bib b/9.2/paper.bib index 1ba7cdf..1a4dd04 100644 --- a/9.2/paper.bib +++ b/9.2/paper.bib @@ -1042,3 +1042,12 @@ doi = {10.1016/0096-3003(82)90191-6} title = {$C^0$ Interior Penalty Methods for Fourth Order Elliptic Boundary Value Problems on Polygonal Domains}, journal = {Journal of Scientific Computing} } + +@Article{clevenger_stokes19, + Title = {Comparison between Algebraic and Matrix-free Geometric Multigrid for a Stokes Problem}, + Author = {Thomas C. Clevenger and Timo Heister}, + Journal = {submitted}, + Year = {2019}, + Url = {https://arxiv.org/abs/1907.06696} +} + diff --git a/9.2/paper.tex b/9.2/paper.tex index dbeaec2..3e3e683 100644 --- a/9.2/paper.tex +++ b/9.2/paper.tex @@ -416,6 +416,7 @@ improvement can be found online), we were able to significantly improve the set up time for large-scale simulations and to solve a Poisson problem with multigrid with \num{2.1e12} unknowns. +\todo[inline]{the figure only shows 2e11 unknowns. Is this a typo? If not, do we have a reference?} Figure~\ref{fig:init_costs} compares timings of simulations of various problem sizes (including set up) on 49,152 MPI ranks using a matrix-free solver~\cite{KronbichlerKormann2019,KronbichlerWall2018}; this solver uses discontinuous elements of @@ -530,18 +531,18 @@ the setup of the multigrid transfer. \end{figure} -\todo[inline]{Timo: Do you want to say something about that the new code has been also applied to solve problems with adaptively refined - meshes with more than \num{4e9} unknowns?} +As part of this effort, we ran benchmarks on the TACC Frontera system, where we were able to apply the matrix-free geometric multigrid framework to a variable viscosity Stokes system and achieved weak and strong scaling up to 114k MPI ranks with up to +\num{2.1e11} unknowns. This is likely the currently largest block system solved with \dealii{} and required various optimizations +and fixes on top of the ones mentioned above: +1) Bug fixes to concurrent point to point communications. +2) Fixes multigrid transfer with adaptive refinement and more than \num{4e9} unknowns. +3) Fixes to index sets in block indices with more than \num{4e9} unknowns. +4) Fixes to computations with more than \num{4e9} active cells. +5) Implementation of IDR(s) solvers to reduce memory overhead. +For more details, see \cite{clevenger_stokes19}. -\todo[inline]{Timo says: We did solve adaptive problems with more than - 4B unknowns before, but some were broken for a while during this - release stage due to the consensus algorithms. But we did not test - systems or block vectors before. But we should not make it sound too - negative.} - -\todo[inline]{Wolfgang says: Should we just not mention any of this at - all? The section stands well on its own.} +\todo[inline]{Timo added the paragraph above. Thoughts on how much we should mention (none of this worked with 9.1)?} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \subsection{Better support for parallel $hp$-adaptive algorithms}