I guess I should explain what I'm trying to do. =) I have an 8 variable system of which one variable is pressure. When the pressure variable is added, I get a very poorly conditioned matrix. A suggestion that was given to me was to under-integrate the pressure variable. So, I was thinking to just attach different quadrature rules to the different variables. But then, when the elem is getting updated, the basis functions would get updated only for their own quadrature point. But for integrals of the equation for the pressure, I would need the basis functions of the other variables to also have values at the pressure quadrature points. Is there a way to do this? Or is there another way I am not thinking of?
Thanks! Andrea On Wed, Apr 8, 2009 at 6:54 PM, Kirk, Benjamin (JSC-EG311) < [email protected]> wrote: > If you mean can the library properly under-integrate, say, the mass matrix > for bilinear lagrange using 1pt quadrature no, but it should be an easy > add... > > That is where the problems come in, right? For example you can solve the > transient heat eqn under-integrated if you do something with the mass > matrix? > > > > ----- Original Message ----- > From: John Peterson <[email protected]> > To: David Knezevic <[email protected]> > Cc: libmesh-users <[email protected]> > Sent: Wed Apr 08 18:49:58 2009 > Subject: Re: [Libmesh-users] Under Integration > > On Wed, Apr 8, 2009 at 6:27 PM, David Knezevic <[email protected]> wrote: > > You could do: > > > > AutoPtr<QBase> qrule = > > fe_type.default_quadrature_rule(dim,extra_quad_order); > > > > where extra_quad_order is negative. > > If you want to achieve "mass lumping" there are also Trapezoidal > (QTrap) rules available. There's also Simpson's Rule (QSimpson) which > may lump the quadratics...? I can't remember exactly how that works. > > -- > John > > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by: > High Quality Requirements in a Collaborative Environment. > Download a free trial of Rational Requirements Composer Now! > http://p.sf.net/sfu/www-ibm-com > _______________________________________________ > Libmesh-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/libmesh-users > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by: > High Quality Requirements in a Collaborative Environment. > Download a free trial of Rational Requirements Composer Now! > http://p.sf.net/sfu/www-ibm-com > _______________________________________________ > Libmesh-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/libmesh-users > ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
