## [Libmesh-users] numbering of multiple variables in coupled PDEs

 [Libmesh-users] numbering of multiple variables in coupled PDEs From: Yujie - 2007-12-18 18:57:44 Attachments: Message as HTML ```Hi, everyone Supposed that I have three variables (U, V, W) in three coupled PDEs (Eq1, Eq2, Eq3). In the final matrix and RHS, their numbering is UEq1, UEq2, UEq3, VEq1, VEq2, VEq3, WEq1, WEq2, WEq3? Thanks a lot. Regards, Yujie ```

 [Libmesh-users] numbering of multiple variables in coupled PDEs From: Yujie - 2007-12-18 18:57:44 Attachments: Message as HTML ```Hi, everyone Supposed that I have three variables (U, V, W) in three coupled PDEs (Eq1, Eq2, Eq3). In the final matrix and RHS, their numbering is UEq1, UEq2, UEq3, VEq1, VEq2, VEq3, WEq1, WEq2, WEq3? Thanks a lot. Regards, Yujie ```
 [Libmesh-users] numbering of multiple variables in coupled PDEs From: John Peterson - 2007-12-18 19:13:50 ```Yujie writes: > Hi, everyone > > Supposed that I have three variables (U, V, W) in three coupled PDEs (Eq1, > Eq2, Eq3). In the final matrix and RHS, their numbering > is UEq1, UEq2, UEq3, VEq1, VEq2, VEq3, WEq1, WEq2, WEq3? Probably something like: [K_UU K_UV K_UW] [U] [K_VU K_VV K_VW] [V] [K_WU K_WV K_WW] [W] but it sounds like you are getting ready to do something ill-advised, such as indexing directly into the solution vector based on and assumed variable ordering. Use the DofMap for this... -J > Thanks a lot. > > Regards, > Yujie ```
 Re: [Libmesh-users] numbering of multiple variables in coupled PDEs From: Roy Stogner - 2007-12-18 20:00:06 ```On Tue, 18 Dec 2007, John Peterson wrote: > Yujie writes: > > Hi, everyone > > > > Supposed that I have three variables (U, V, W) in three coupled PDEs (Eq1, > > Eq2, Eq3). In the final matrix and RHS, their numbering > > is UEq1, UEq2, UEq3, VEq1, VEq2, VEq3, WEq1, WEq2, WEq3? > > Probably something like: > > [K_UU K_UV K_UW] [U] > [K_VU K_VV K_VW] [V] > [K_WU K_WV K_WW] [W] This is the default behavior. If you want Dofs to be sorted by node instead (giving a vector like [U1 V1 W1 U2 V2 W2 U3 V3 W3...]) there's a little used command line option "--node_major_dofs" to do so. --- Roy ```