- Global quadrant number by Ethan Hereth
- Re: [p4est] Global quadrant number by Michael Lahnert
- Re: [p4est] Global quadrant number by Ethan Hereth

- From:
- Ethan Hereth
- Date:
- 2015-08-24 @ 01:17

Gentlemen, I'm trying to validate some research code I have that uses p4est. Specifically I am trying to validate the compressed row storage and linear system solver I have implemented for my implicit scheme. I'm having some trouble getting my parallel implicit code to work so I want to try to see if I can get the same answer to a global system in serial and in parallel. Is there a way to get a 'global' quadrant number in parallel? I.e., can I back out the index a quadrant would have gotten if the parallel p4est had been created in serial? I dug around in the headers some but I couldn't quickly find anything that looked useful. Forgive me if I'm overlooking something obvious. Thank you for your help and, once again, thanks for the great software. Ethan Alan

- From:
- Michael Lahnert
- Date:
- 2015-08-24 @ 07:01

Hi Ethan, On Sun, 2015-08-23 at 21:17 -0400, Ethan Hereth wrote: > Is there a way to get a > 'global' quadrant number in parallel? I.e., can I back out the index a > quadrant would have gotten if the parallel p4est had been created in serial? I > dug around in the headers some but I couldn't quickly find anything that > looked useful. Forgive me if I'm overlooking something obvious. if you are just interested in verifying you have the right cells in your scheme you might look into x, y, and z (if 3D or P4_TO_P8) of p4(8)est_quadrant_t. If you want to recover a cell's index, I think you can make use of the space -filling curve, i.e. something like add number of quadrants of all processors with lesser rank + local tree offset + local index (see figure 2.1 of [1]). Note however, that I did not try this in an actual code-snippet. Best regards Michael [1] p4est: Scalable Algorithms For Parallel Adaptive Mesh Refinement on Forests of Octrees by Carsten Burstedde, Lucas Wilcox, and Omar Ghattas; http://p4est.github.io/papers/BursteddeWilcoxGhattas11.pdf -- Dipl.-Inf. Michael Lahnert Simulation großer Systeme Institut für Parallele und Verteilte Systeme, Universität Stuttgart Universitätsstraße 38 70569 Stuttgart | Germany Tel: +49 (0)711 685 88560

- From:
- Ethan Hereth
- Date:
- 2015-09-17 @ 18:03

I'm sorry to just now respond. I appreciate your answer. After having sent the email it occurred to me that I could probably do something like you suggested to figure this out. I've been swamped haven't had the chance to try it out yet, and now I'm not sure I'll need to anymore. Thanks for your time though. Ethan Alan Ethan Alan On Mon, Aug 24, 2015 at 3:01 AM, Michael Lahnert < michael.lahnert@ipvs.uni-stuttgart.de> wrote: > Hi Ethan, > > On Sun, 2015-08-23 at 21:17 -0400, Ethan Hereth wrote: > > Is there a way to get a > > 'global' quadrant number in parallel? I.e., can I back out the index a > > quadrant would have gotten if the parallel p4est had been created in > serial? I > > dug around in the headers some but I couldn't quickly find anything that > > looked useful. Forgive me if I'm overlooking something obvious. > > if you are just interested in verifying you have the right cells in your > scheme > you might look into x, y, and z (if 3D or P4_TO_P8) of p4(8)est_quadrant_t. > > If you want to recover a cell's index, I think you can make use of the > space > -filling curve, i.e. something like add number of quadrants of all > processors > with lesser rank + local tree offset + local index (see figure 2.1 of > [1]). Note > however, that I did not try this in an actual code-snippet. > > Best regards > Michael > > [1] p4est: Scalable Algorithms For Parallel Adaptive Mesh Refinement on > Forests > of Octrees by Carsten Burstedde, Lucas Wilcox, and Omar Ghattas; > http://p4est.github.io/papers/BursteddeWilcoxGhattas11.pdf > > -- > Dipl.-Inf. Michael Lahnert > Simulation großer Systeme > Institut für Parallele und Verteilte Systeme, Universität Stuttgart > Universitätsstraße 38 > 70569 Stuttgart | Germany > > Tel: +49 (0)711 685 88560 > >