[petsc-users] Saving solution with monitor function

[Matthew Knepley]

On Wed, Dec 14, 2022 at 5:43 PM Guglielmo, Tyler Hardy <guglielmo2 at llnl.gov>
wrote:

> Ah beautiful, thanks for showing me these.  Apologies for bugging you all
> with these questions.  Having to learn a ton of subroutines…
>
>
>
> Btw is there a matrix addition function for M = a*M_1 + b*M_2, or one
> similar to MatAXPY that does not overwrite the Y matrix, i.e. M = a*X + Y ?
>

We do not have that. You might MatCopy(Y, M) and then MatAXPY()

  Thanks,

     Matt


>
>
> All the best,
>
> Tyler
>
>
>
> *From: *Barry Smith <bsmith at petsc.dev>
> *Date: *Wednesday, December 14, 2022 at 12:51 PM
> *To: *Guglielmo, Tyler Hardy <guglielmo2 at llnl.gov>
> *Cc: *Matthew Knepley <knepley at gmail.com>, petsc-users at mcs.anl.gov <
> petsc-users at mcs.anl.gov>
> *Subject: *Re: [petsc-users] Saving solution with monitor function
>
>
>
>   See, for example
> https://petsc.org/release/docs/manualpages/TS/TSTrajectoryGetVecs/
> <https://urldefense.us/v3/__https:/petsc.org/release/docs/manualpages/TS/TSTrajectoryGetVecs/__;!!G2kpM7uM-TzIFchu!g_m1lKCrhOfOZS5ADCQjmV_Ma8U7ZZJpCFHg6T7Lu10M0jl8pC_5yXYCyQIH7-4dIko$>
>  and
> https://petsc.org/release/docs/manualpages/TS/TSTrajectoryGetUpdatedHistoryVecs/
> <https://urldefense.us/v3/__https:/petsc.org/release/docs/manualpages/TS/TSTrajectoryGetUpdatedHistoryVecs/__;!!G2kpM7uM-TzIFchu!g_m1lKCrhOfOZS5ADCQjmV_Ma8U7ZZJpCFHg6T7Lu10M0jl8pC_5yXYCyQIHEECbTaM$>
>
>
>
>
>   One does not directly access the data inside the trajectory; one calls
> functions in the API to obtained desired information.  If you need specific
> information that it does not currently provide we can attempt to provide
> additional functionality.
>
>
>
>
>
>   Barry
>
>
>
>
>
> On Dec 14, 2022, at 1:07 PM, Guglielmo, Tyler Hardy via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>
>
> Thanks Matt,
>
>
>
> I’m a bit confused on where the trajectory is being stored in the
> TSTrajectory object.
>
>
>
> Basically I have run
>
>
>
> TSSetSaveTrajectory(ts);
>
> …
>
> TSSolve(ts, x);
>
> TSTrajectory tj;
>
> TSGetTrajectory(ts, &tj);
>
> TSTrajectorySetType(tj, ts, TSTRAJECTORYMEMORY);
>
>
>
> How is the object supposed to be accessed to find the entire trajectory?
> I couldn’t find a clear example of where this is laid out in the
> documentation.
>
>
>
> The TSTrajectory object looks like some complicated struct, but parsing
> which pointer is pointing to the solution has alluded me.
>
>
>
> Thanks for your time!
>
>
>
> Best,
>
> Tyler
>
>
>
>
>
> *From: *Matthew Knepley <knepley at gmail.com>
> *Date: *Tuesday, December 13, 2022 at 6:41 AM
> *To: *Guglielmo, Tyler Hardy <guglielmo2 at llnl.gov>
> *Cc: *petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
> *Subject: *Re: [petsc-users] Saving solution with monitor function
>
> On Tue, Dec 13, 2022 at 8:40 AM Guglielmo, Tyler Hardy via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> Hi all,
>
>
>
> I am a new PETSc user (and new to MPI in general), and was wondering if
> someone could help me out with what I am sure is a basic question (if this
> is not the appropriate email list or there is a better place please let me
> know!).
>
>
>
> Basically, I am writing a code that requires a solution to an ODE that
> will be used later on during runtime.  I have written the basic ODE solver
> using TSRK, however I haven’t thought of a good way to store the actual
> solution at all time steps throughout the time evolution.  I would like to
> avoid writing each time step to a file through the monitor function, and
> instead just plug each time step into an array.
>
>
>
> How is this usually done?  I suppose the user defined struct that gets
> passed into the monitor function could contain a pointer to an array in
> main?  This is how I would do this if the program wasn’t of the MPI
> variety, but I am not sure how to properly declare a pointer to an array
> declared as Vec and built through the usual PETSc process.  Any tips are
> greatly appreciated
>
>
>
> I think this is what TSTrajectory is for. I believe you want
> https://petsc.org/main/docs/manualpages/TS/TSTRAJECTORYMEMORY/
> <https://urldefense.us/v3/__https:/petsc.org/main/docs/manualpages/TS/TSTRAJECTORYMEMORY/__;!!G2kpM7uM-TzIFchu!irkbXWpYDosRslumKjVGCqxHkKyU-riye4i1dWe58HYH_sFxImRj33gOkhB2sgd_duk$>
>
>
>
>   Thanks,
>
>
>
>       Matt
>
>
>
> Thanks for your time,
>
> Tyler
>
>
>
> +++++++++++++++++++++++++++++
>
> Tyler Guglielmo
>
> Postdoctoral Researcher
>
> Lawrence Livermore National Lab
>
> Office: 925-423-6186
>
> Cell: 210-480-8000
>
> +++++++++++++++++++++++++++++
>
>
>
>
> --
>
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
>
>
> https://www.cse.buffalo.edu/~knepley/
> <https://urldefense.us/v3/__http:/www.cse.buffalo.edu/*knepley/__;fg!!G2kpM7uM-TzIFchu!irkbXWpYDosRslumKjVGCqxHkKyU-riye4i1dWe58HYH_sFxImRj33gOkhB27-uscIw$>
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20221214/3cac9c17/attachment-0001.html>