"Kong, Fande" <[email protected]> writes: > On Sun, Jul 23, 2017 at 5:31 PM, Jed Brown <[email protected]> wrote: > >> Barry Smith <[email protected]> writes: >> >> > Anything stopping us from making a PETSc release? >> >> I need to finish/test the SF support for MPIUNI that you asked me to do >> in June. >> >> I've also been meaning to add hashtable support for assembly when people >> don't preallocate. I think we should make it automatic. It isn't much >> code and would save the weekly assembly performance emails and would >> help a lot for model coupling where our preallocation interfaces (for >> off-diagonal blocks) are terrible and the requisite user code is >> arguably dirtier than assembly itself. >> > > > I am so interested in this. I am having hard time to make the > preallocation right for users because they have all kinds of crazy physics > that coupling different PDEs together based on their own rules. So if we > could make the preallocate work automatically, it would be great. > > If we have this code in, the preallocation is not necessary for users any > more? Still worthwhile to have the right preallocation if possible?
Correct. The hash needs to be converted to a matrix so the maximum memory usage is about double that of precise preallocation in advance. But this is only the first assembly, which is usually done before setting up preconditioners and Krylov spaces so in most cases would not significantly affect the maximum memory usage of the application.
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