Re: [deal.II] Control over the "valence" of p4est distributed meshes

2022-12-08 Thread Wolfgang Bangerth

On 12/8/22 14:46, blais...@gmail.com wrote:


I know that P4est as a partitioner has limitations compared to other 
approaches like Metis or Scotch. However, I was wondering if there was anyway 
to penalize the partitioner in order to generate the smaller valence that is 
possible? Sometimes we end up with interfaces between processors that are 
substantially big (or islands of a few cells). The issue is that for our 
particle code, this generates a ton of Ghost particles and these particles 
generate additional cost (collisions become significantly more expensive to 
calculate because we cannot apply newton's third law for a collision. The 
calculation becomes essentially duplicated).


I was wondering if there was any ways to "force" or ensure that the interfaces 
between subdomains remained relatively well-posed?


Bruno:
No, p4est partitions a space-filling curve. You can select where the partition 
points along this one-dimensional line are (by choosing weights for each 
cell), but you can't change the curve or what subdomain interfaces this creates.


If that's what you need, you'll have to use the fullydistributed triangulation 
class that allows you to do that.


Best
 W.

--

Wolfgang Bangerth  email: bange...@colostate.edu
   www: http://www.math.colostate.edu/~bangerth/


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[deal.II] Control over the "valence" of p4est distributed meshes

2022-12-08 Thread blais...@gmail.com
Dear all,
I hope you are well.

I know that P4est as a partitioner has limitations compared to other 
approaches like Metis or Scotch. However, I was wondering if there was 
anyway to penalize the partitioner in order to generate the smaller valence 
that is possible? Sometimes we end up with interfaces between processors 
that are substantially big (or islands of a few cells). The issue is that 
for our particle code, this generates a ton of Ghost particles and these 
particles generate additional cost (collisions become significantly more 
expensive to calculate because we cannot apply newton's third law for a 
collision. The calculation becomes essentially duplicated). 

I was wondering if there was any ways to "force" or ensure that the 
interfaces between subdomains remained relatively well-posed?

Thank you very much!
Bruno

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