Dear Deyan, 

the answer to your question is “it depends”. And it also depends on what you 
mean by “share”. 

Let’s start in order: 

1. what type of quadrature points are you using to perform integration? If you 
are using QGauss formulas, they only have interior points, so technically none 
of these points live on the boundary of your cells, and therefore none of these 
are shared.

2. if you use QGaussLobatto formulas, where there are indeed quadrature points 
on the boundary, they are physically located on the boundary, but they are 
defined independently cell by cell, i.e., they are not “shared” by cells

When you loop over all cells, you will make computations on those points twice 
(or as many times as there are neighbours that share the same location), and 
generally speaking, this is really what you want to happen, since on those 
points you have, in general, discontinuous quantities (i.e., gradients of basis 
functions/material coefficients, etc.), so you really want to treat each of 
these points separately on each cell, to compute correctly the integral on that 
given cell, irrespective of the values of the integrands in the neighbouring 
cells.

L. 



> On 19 Apr 2025, at 22:00, Deyan Mihaylov <deyan.ivov.mihay...@gmail.com> 
> wrote:
> 
> Hi All, 
> 
> I was wondering if there was a way to know how many cells a certain 
> quadrature point is shared by. Let's say I am iterating over square cells in 
> 2D and I have 4 quad points in each cell. When I go into cell one, and let's 
> say that cell is on the corner of my domain, is there a way to know that 1 of 
> my quadrature points belongs to only that cell (the quad point in the corner) 
> , 2 of my quad points are shared by 2 cells, and the 4th quad point is shared 
> by 4 cells?  
> 
> See attached pic of what i am trying to explain. 
> 
> Sorry if this is an elementary question, but I just spent hours looking for 
> something like that but couldn't find it.
> 
> Thank you in advance!
> 
> Deyan
> 
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