## [Libmesh-devel] Periodic BCs with Offset

 [Libmesh-devel] Periodic BCs with Offset From: Derek Gaston - 2012-09-11 17:36:48 Attachments: Message as HTML ```One of our users is looking for the ability to do Periodic BCs... but where instead of have _equality_ on either side of the periodic boundary you instead have a constant offset. So if u_i is periodic with u_j you would then have the constraint that u_j = u_i + c ... where c is that specified offset. What's really tricky is that they want a different constant value for each variable. Anyone see a way to make that happen? Derek ```

 [Libmesh-devel] Periodic BCs with Offset From: Derek Gaston - 2012-09-11 17:36:48 Attachments: Message as HTML ```One of our users is looking for the ability to do Periodic BCs... but where instead of have _equality_ on either side of the periodic boundary you instead have a constant offset. So if u_i is periodic with u_j you would then have the constraint that u_j = u_i + c ... where c is that specified offset. What's really tricky is that they want a different constant value for each variable. Anyone see a way to make that happen? Derek ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Roy Stogner - 2012-09-11 17:44:42 ```On Tue, 11 Sep 2012, Derek Gaston wrote: > One of our users is looking for the ability to do Periodic BCs... but where instead of have _equality_ on either side of the periodic boundary you > instead have a constant offset. > So if u_i is periodic with u_j you would then have the constraint that u_j = u_i + c ... where c is that specified offset. > > What's really tricky is that they want a different constant value for each variable. > > Anyone see a way to make that happen? It'd actually be pretty easy now that the heterogenous constraints are in - we'd just want to add "offset" values to the PeriodicBoundary class and respect that when constructing the constraint equations. The main problem is: isn't the new PBC code still failing some of your tests? Last I heard, John still had a MOOSE regression test breaking but hadn't been able to distill it down into a libMesh-only failure case to send me. --- Roy ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Cody Permann - 2012-09-11 19:15:58 Attachments: Message as HTML ```On Tue, Sep 11, 2012 at 11:44 AM, Roy Stogner wrote: > > On Tue, 11 Sep 2012, Derek Gaston wrote: > > > One of our users is looking for the ability to do Periodic BCs... but > where instead of have _equality_ on either side of the periodic boundary you > > instead have a constant offset. > > So if u_i is periodic with u_j you would then have the constraint that > u_j = u_i + c ... where c is that specified offset. > > > > What's really tricky is that they want a different constant value for > each variable. > > > > Anyone see a way to make that happen? > > It'd actually be pretty easy now that the heterogenous constraints are > in - we'd just want to add "offset" values to the PeriodicBoundary > class and respect that when constructing the constraint equations. > > The main problem is: isn't the new PBC code still failing some of your > tests? Last I heard, John still had a MOOSE regression test breaking > but hadn't been able to distill it down into a libMesh-only failure > case to send me. > So we do still have one test that's failing. John coded up the example in pure libMesh code and it works so the problem doesn't appear to be on your end. However there are a few differences in the way MOOSE solves it and Johns example: for one we solve every problem with a transient nonlinear system using JFNK which is of course different from the simple example John has already coded up using a linear system. We were down to looking at differences in the system matrix to try to figure out why things were different, but will need more time to narrow down the issue. I think we've decided that we are going to put this one problem to the side for now since it has been a hefty time sink and move forward until we have some more downtime. The remaining PBCs issues appear to be solved using your latest (uncommitted?) patch. We are going to work on updating all of our users to the current head of libMesh barring any other issues. Thanks for working on this for us! Cody > --- > Roy > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Libmesh-devel mailing list > Libmesh-devel@... > https://lists.sourceforge.net/lists/listinfo/libmesh-devel > ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Roy Stogner - 2012-09-11 19:57:44 ```On Tue, 11 Sep 2012, Cody Permann wrote: > So we do still have one test that's failing.  John coded up the > example in pure libMesh code and it works so the problem doesn't > appear to be on your end.  However there are a few differences in > the way MOOSE solves it and Johns example: for one we solve every > problem with a transient nonlinear system using JFNK which is of > course different from the simple example John has already coded up > using a linear system.  We were down to looking at differences in > the system matrix to try to figure out why things were different, > but will need more time to narrow down the issue. Is it possible that you're combining PBC-generated constraints with user-generated or Dirichlet-generated constraints on the same node? That's the one case I haven't tested well enough yet and wouldn't trust a priori. > I think we've decided that we are going to put this one problem to > the side for now since it has been a hefty time sink and move > forward until we have some more downtime.  The remaining PBCs issues > appear to be solved using your latest (uncommitted?) patch.   Good to hear. I'll change that from uncommitted to committed now, then. > We are going to work on updating all of our users to the current > head of libMesh barring any other issues. Thanks! If we're no longer forked, then I'll soon also be committing a few other simple-but-voluminous changes (e.g. the libmesh_assert_equal macro I mentioned on -devel a while ago) that I'd been holding off on. > Thanks for working on this for us! No trouble. It wasn't pure altruism. The race condition in threaded PBCs has been causing our BuildBot tests fits for a while, and although in hindsight it might have been more time-efficient for me to simply disable those tests, at the time it didn't look like making asynchronous PBC calculations robust was going to be so hard... --- Roy```
 Re: [Libmesh-devel] Periodic BCs with Offset From: John Peterson - 2012-09-12 15:06:56 ```On Tue, Sep 11, 2012 at 1:57 PM, Roy Stogner wrote: > > On Tue, 11 Sep 2012, Cody Permann wrote: > >> I think we've decided that we are going to put this one problem to >> the side for now since it has been a hefty time sink and move >> forward until we have some more downtime. The remaining PBCs issues >> appear to be solved using your latest (uncommitted?) patch. > > > Good to hear. I'll change that from uncommitted to committed now, > then. Is this patch in as of r6003? -- John ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Roy Stogner - 2012-09-12 16:39:58 ```On Wed, 12 Sep 2012, John Peterson wrote: > On Tue, Sep 11, 2012 at 1:57 PM, Roy Stogner wrote: >> >> On Tue, 11 Sep 2012, Cody Permann wrote: >> >>> I think we've decided that we are going to put this one problem to >>> the side for now since it has been a hefty time sink and move >>> forward until we have some more downtime. The remaining PBCs issues >>> appear to be solved using your latest (uncommitted?) patch. >> >> Good to hear. I'll change that from uncommitted to committed now, >> then. > > Is this patch in as of r6003? It's in now, r6008. --- Roy ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Robert - 2012-09-18 09:56:16 ```On Tue, Sep 11, 2012 at 12:44:35PM -0500, Roy Stogner wrote: > > On Tue, 11 Sep 2012, Derek Gaston wrote: > > > One of our users is looking for the ability to do Periodic BCs... but where instead of have _equality_ on either side of the periodic boundary you > > instead have a constant offset. > > So if u_i is periodic with u_j you would then have the constraint that u_j = u_i + c ... where c is that specified offset. > > > > What's really tricky is that they want a different constant value for each variable. > > > > Anyone see a way to make that happen? > > It'd actually be pretty easy now that the heterogenous constraints are > in - we'd just want to add "offset" values to the PeriodicBoundary > class and respect that when constructing the constraint equations. > > The main problem is: isn't the new PBC code still failing some of your > tests? Last I heard, John still had a MOOSE regression test breaking > but hadn't been able to distill it down into a libMesh-only failure > case to send me. As this main problem is some kind of resolved according to the mailinglist, has anyone already coded this "easy" addition? Will this also work for the new vector_fe stuff? I am currently using the displacements (u,v,w) as primary variables and want to switch to using the nodes position (x,y,z) as primary variables. Robert > --- > Roy > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Libmesh-devel mailing list > Libmesh-devel@... > https://lists.sourceforge.net/lists/listinfo/libmesh-devel ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Roy Stogner - 2012-09-18 13:24:09 ```On Tue, 18 Sep 2012, Robert wrote: > On Tue, Sep 11, 2012 at 12:44:35PM -0500, Roy Stogner wrote: > >> It'd actually be pretty easy now that the heterogenous constraints are >> in - we'd just want to add "offset" values to the PeriodicBoundary >> class and respect that when constructing the constraint equations. >> >> The main problem is: isn't the new PBC code still failing some of your >> tests? Last I heard, John still had a MOOSE regression test breaking >> but hadn't been able to distill it down into a libMesh-only failure >> case to send me. > > As this main problem is some kind of resolved according to the mailinglist, > has anyone already coded this "easy" addition? No. I'm the one it'd be easy for, but I'm already behind on other urgent things, so not sure when I'll get to it. > Will this also work for the new vector_fe stuff? It should - Paul already took care of all the hard bits when he got vector Dirichlet boundaries working. > I am currently using the displacements (u,v,w) as primary variables and > want to switch to using the nodes position (x,y,z) as primary variables. That's certainly a good reason to want vector PBCs with offsets. If you want to try and speed up the works: write a patch with the API and test case yourself (i.e. give PeriodicBoundary similar functors to DirichletBoundary, add a new vector_fe example using them) and I'll find it slightly easier and much more motivating to see if I can get the implementation passing that test this weekend. --- Roy ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Paul T. Bauman - 2012-09-18 14:13:59 Attachments: Message as HTML ```On Tue, Sep 18, 2012 at 8:24 AM, Roy Stogner wrote: > > Will this also work for the new vector_fe stuff? > > It should - Paul already took care of all the hard bits when he got > vector Dirichlet boundaries working. > I'm not sure I actually did anything for the periodic constraints yet. If you can cook up an example I can test with, I'll go ahead and finish that off (at least for LAGRANGE_VEC elements). > > > I am currently using the displacements (u,v,w) as primary variables and > > want to switch to using the nodes position (x,y,z) as primary variables. > I'm curious as to why you're going this route. When I played with these problems awhile back (granted, not with libMesh), I always found it easier to deal with the displacements rather than the node positions. Best, Paul ```
 Re: [Libmesh-devel] Periodic BCs with Offset From: Roy Stogner - 2012-09-18 15:54:08 ```On Tue, 18 Sep 2012, Paul T. Bauman wrote: > On Tue, Sep 18, 2012 at 8:24 AM, Roy Stogner wrote: > > > Will this also work for the new vector_fe stuff? > > > > It should - Paul already took care of all the hard bits when he got > > vector Dirichlet boundaries working. > > I'm not sure I actually did anything for the periodic constraints > yet. If you can cook up an example I can test with, I'll go ahead > and finish that off (at least for LAGRANGE_VEC elements). You didn't do anything for the periodic constraints, but it should generalize easily enough from what you did for the dirichlet constraints. --- Roy ```