Re: [Libmesh-users] P2-iso-P1

[Liang <goe...@gm...>]

>
> Gauss-Legendre rules of high enough order give exact results for
> polynomial non-macroelements, but on a macroelement the reduced
> smoothness between subelements hurts you.  The easiest (albeit not the
> most efficient) solution for piecewise-polynomial macroelements is to
> just combine a (translated and reweighted) Gauss rule on each
> subelement.
>
> libMesh has a bunch of non-Gauss-Legendre rules for general elements
> available too; some for verification and underintegration, some just
> because there are multiple ways to do quadrature in 2D/3D with
> different tradeoffs.  Check the source code first if you're curious;
> John has most of it pretty well documented.
> ---
> Roy
>
Interesting, I appreciate your clear explanation, yes I just know 
something about basic non-macroelement from the  textbook. it is obvious 
that libmesh is not only a software but also a wonderful modern FEA 
tutorial. there are already lots of libmesh source codes on my list. Thanks!

Liang