From: bangerth Date: Wed, 21 Sep 2011 19:55:43 +0000 (+0000) Subject: Reference step-21 at one place. X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=88afb2d45ad7d1b34ee66dc02ec76a68de6296e8;p=dealii-svn.git Reference step-21 at one place. git-svn-id: https://svn.dealii.org/trunk@24358 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/examples/step-31/doc/intro.dox b/deal.II/examples/step-31/doc/intro.dox index 715628b799..423e6bde2b 100644 --- a/deal.II/examples/step-31/doc/intro.dox +++ b/deal.II/examples/step-31/doc/intro.dox @@ -863,7 +863,10 @@ $F_T$ depend on the already computed solution $U^n$, in the first case through the time step (that depends on $U^n$ because it has to satisfy a CFL condition). So we can only assemble it once we've already solved the top left $2\times 2$ block Stokes system, and once we've moved on to the temperature -equation we don't need the Stokes part any more. Furthermore, we don't +equation we don't need the Stokes part any more; the fact that we +build an object for a matrix that never exists as a whole in memory at +any given time led us to jumping through some hoops in step-21, so +let's not repeat this sort of error. Furthermore, we don't actually build the matrix $C$: Because by the time we get to the temperature equation we already know $U^n$, and because we have to assemble the right hand side $F_T$ at this time anyway, we simply move the term $CU^n$ to the right