Work at SourceForge, help us to make it a better place! We have an immediate need for a Support Technician in our San Francisco or Denver office.

## libmesh-users

 [Libmesh-users] Mixed vs Homogeneous multivariable finite element types From: Kirk, Benjamin (JSC-EG311) - 2012-12-05 20:41:27 ```I'm working some optimizations with how libMesh stores & allocates degree of freedom indices when there are multiple variables associated with a given System. These generically fall into two categories - (1) homogeneous types, where there are multiple variables but they all have the same finite element type, and (2) mixed types, where there are different variables with different finite element types as well (like Taylor-Hood Q2/Q1 incompressible NS, for example) for both cases, we could do some optimization in how we store degree of freedom indices & do things like compute the sparse matrix graph. for case (1) in particular, we could also take advantage of the identical block-structure of the linear system as well and use e.g. PETSc's block matrix and vector support. So my question is, for your multivariable systems, are they typically of type (1) or (2)? How many variables and what types? My reason in asking is because some of the optimizations are easier for case (1), which is where I plan to start, but don't want to do anything that would preclude additional optimization for (2), especially if there are people with ~5 or more variables of different finite element types in a system. Thanks, -Ben ```
 Re: [Libmesh-users] [Libmesh-devel] Mixed vs Homogeneous multivariable finite element types From: Derek Gaston - 2012-12-05 22:00:44 ```OMG. This would be awesome. I've actually got a user that has been breathing down our necks for this optimization. In his case he is solving with over 2,000 variables that are all of exactly the same type. Generally, first or second order Lagrange (although he does some DG as well). We also have other users solving with 20-200 variables of the same kind (again, usually first or second order Lagrange) but they might also have 1-4 variables of another kind (like cubic hermites) mixed in - but not always. ANY optimizations along these lines would be truly awesome! Derek Sent from my iPhone On Dec 5, 2012, at 1:41 PM, "Kirk, Benjamin (JSC-EG311)" wrote: > I'm working some optimizations with how libMesh stores & allocates degree of freedom indices when there are multiple variables associated with a given System. These generically fall into two categories - > > (1) homogeneous types, where there are multiple variables but they all have the same finite element type, and > (2) mixed types, where there are different variables with different finite element types as well (like Taylor-Hood Q2/Q1 incompressible NS, for example) > > for both cases, we could do some optimization in how we store degree of freedom indices & do things like compute the sparse matrix graph. > > for case (1) in particular, we could also take advantage of the identical block-structure of the linear system as well and use e.g. PETSc's block matrix and vector support. > > So my question is, for your multivariable systems, are they typically of type (1) or (2)? How many variables and what types? > > My reason in asking is because some of the optimizations are easier for case (1), which is where I plan to start, but don't want to do anything that would preclude additional optimization for (2), especially if there are people with ~5 or more variables of different finite element types in a system. > > Thanks, > > -Ben > > > > > ------------------------------------------------------------------------------ > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > Libmesh-devel mailing list > Libmesh-devel@... > https://lists.sourceforge.net/lists/listinfo/libmesh-devel ```
 Re: [Libmesh-users] [Libmesh-devel] Mixed vs Homogeneous multivariable finite element types From: Roy Stogner - 2012-12-06 16:50:35 ```On Wed, 5 Dec 2012, Derek Gaston wrote: > In his case he is solving with over 2,000 variables > > We also have other users solving with 20-200 variables of the same It would be interesting to know of other places where users are greatly exceeding our original estimates of what "N" might be in cases where we're designing O(f(N)) algorithms. E.g. I just blithely told Vikram not to worry about writing an O(N_vectors_per_System) bit of code, for instance, because in my typical codes (solution, old solution, rhs, qoi0-adjoint, qoi1-adjoint...) N might be around 6, but perhaps the reduced-basis people or others vastly exceed that. (In this case the constant is small and the code isn't in any inner loops so he's probably fine even for N=6000, but you see the general idea). --- Roy ```