Hello,Ben,
I change my libmesh to SVN code and the implicit part works well with
--implicit_neighbor_dofs on the command line,
the first step is much faster than libmesh0.62.
Thank you very much.
Kirk, Benjamin (JSC-EG) 写道:
> Can you try running the code with --implicit_neighbor_dofs on the
> command line?
> By default the matrix sparsity is computed assuming continuous shape
> functions, but for a DG forumation this is not a good assumption.
> Let me know if that works for you, if so we can look at putting
> something more sophisticated in the library to detect this situation
> and handling it automatically.
> -Ben
>
> ------------------------------------------------------------------------
> *From:* [EMAIL PROTECTED] on behalf of Roy
> Stogner
> *Sent:* Sun 5/11/2008 10:31 PM
> *To:* luyi
> *Cc:* [email protected]
> *Subject:* Re: [Libmesh-users] about the long time for the assemble of
> first step!
>
>
> On Mon, 12 May 2008, luyi wrote:
>
> > Now I write a DG programme on libmesh, when I use the FIRST or higher
> > order basis, the first step is too slow,
> > besides this everything is ok, I use XYZ basis and I check the code by
> > perf_log, the time ratio is up to snuff.
>
> The first time step (especially in a non-adaptive run) has some
> overhead that later timesteps don't, but it's also possible you've
> found a bug. If we're not preallocating the sparse matrix with the
> correct sparsity pattern, for example, PETSc might take quite a long
> time on the first assembly.
>
> Could you run your code for only one time step and check the perf_log
> on that, to see what part of the code is taking too long?
> ---
> Roy
>
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