From e8bdc3a7a54e44181323f9d210af852be5cd3ae6 Mon Sep 17 00:00:00 2001 From: Wolfgang Bangerth Date: Mon, 1 Jul 2024 17:10:14 -0600 Subject: [PATCH] Leave a note about DAEs. --- examples/step-86/doc/intro.dox | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/examples/step-86/doc/intro.dox b/examples/step-86/doc/intro.dox index 7fe39d2cd5..b505a96fda 100644 --- a/examples/step-86/doc/intro.dox +++ b/examples/step-86/doc/intro.dox @@ -272,6 +272,15 @@ provide the ability to take a solution vector and set its constrained (algebraic) entries to their correct values; for us, that will mean setting boundary values and hanging node constraints correctly. +(We note that when dealing with Differential-Algebraic Equations (DAEs), +the algebraic components identified by the first callback mentioned +above contain hanging nodes, Dirichlet boundary nodes, *and degrees +of freedom for which the equation does not provide time derivatives*. +This is not of concern to us here, and so we will not dwell on +the issue -- or the fact that the second callback in the case of DAEs +should set only a subset of the algebraic components -- and instead +refer to the examples shown in the SUNDIALS::IDA class documentation.) +

Complication 2: Mesh refinement

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