From: Matthias Maier Date: Fri, 29 May 2020 23:47:30 +0000 (-0500) Subject: reword step-69 slightly X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6627d8695126fc3eeeaa44915553ae6338bf11cc;p=release-papers.git reword step-69 slightly --- diff --git a/9.2/paper.tex b/9.2/paper.tex index 3855519..6b133db 100644 --- a/9.2/paper.tex +++ b/9.2/paper.tex @@ -875,17 +875,26 @@ pre and post operations, which can be passed to to the matrix-vector product to increase data locality. \item \texttt{step-69} presents a first-order scheme solving compressible -Euler's equations of gas dynamics using a graph-based scheme. The time-update -at each node requires the evaluation of a right-hand side that depends -(nonlinearly) on information from the previous time-step that spans more than -one cell. Therefore, assembly loops operate directly on the sparsity graph in -order to retrieve information from the entire stencil associated to each -node. From a programming perspective, \texttt{step-69} features a number of -techniques that are of interest for a wider audience: It discusses a hybrid -thread and MPI parallelized scheme with efficient (MPI node) local -numbering of degrees of freedom. It showcases how to perform asynchronous -write-out of results using a background thread with \texttt{std::async}, -and discusses a simple but effective checkpointing and restart technique. +Euler's equations of gas dynamics with a graph-viscosity stabilization +technique. Beside the usual conservation properties of mass, momentum and +total energy, the method also guarantees that the constructed solution +obeys pointwise stability constraints (positivity of density, internal +energy and a local minimum principle on the specific entropy). As such +\text{step-69} is strictly speaking more a collocation-type discretization +than a variational formulation, even though it is implemented with finite +elements. + +The time-update at each node requires the evaluation of a right-hand side +that depends (nonlinearly) on information from the previous time-step that +spans more than one cell. Therefore, assembly loops operate directly on the +sparsity graph in order to retrieve information from the entire stencil +associated to each node. From a programming perspective, \texttt{step-69} +features a number of techniques that are of interest for a wider audience: +It discusses a hybrid thread and MPI parallelized scheme with efficient +(MPI node) local numbering of degrees of freedom. It showcases how to +perform asynchronous write-out of results using a background thread with +\texttt{std::async}, and discusses a simple but effective checkpointing and +restart technique. \item \texttt{step-70} \todo[inline]{Luca, please write.}