On this topic, we should become much more adamant, at least in documentation and maybe also in naming about which arguments are scale-free and which are scale-dependent. Internally, we (Peter and I) have a system that is being followed carefully, including in the examples that we write. Things compose well when these unwritten guidelines are followed.
On Thu, Jul 19, 2012 at 1:25 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > On Thu, Jul 19, 2012 at 1:19 PM, Barry Smith <bsmith at mcs.anl.gov> wrote: > >> Why not implement it using PetscObjectQuery()/PetscObjectCompose()? and >> not have to introduce a whole new datatype DMNamedVecLink linked list and >> other crap? >> > > The only reason this thing has to exist, and it really has to exist in > some form, is that we have a reference loop. For example, the SNES Vec X is > obtained from the DM (thus X references the DM), but must be made available > to the KSP callback that uses the DM. If we attached X to the DM, then we > would have a loop X -> DM -> X. Same for the TS vector needed in > SNESComputeFunction. > > The general form of PetscObjectCompose allowing reference loops is > terribly dangerous and imprecise (you end up implementing a sort of limited > garbage collector that periodically looks for loops, but that is super > dangerous in parallel because you need determinism in destruction). > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120719/54ede034/attachment.html>
