Hi,

Sorry for the late reply but I was trying to work around my problem. 

As you mentioned, it may not generally matter how the constraint matrix is 
built but I have been working on a problem that involves Periodic Boundary 
conditions with inhomogeneity. So, here it becomes important for me to 
declare slave and master correctly. As I am unable to find the origin of 
why the order got reversed for the same problem but different version of 
dealii, I am unable to solve the problem using my code (which was otherwise 
working correctly for the earlier version of dealii). 

Looking forward to some help.

Kind Regards,
Aditya
On Monday, 8 November 2021 at 23:06:58 UTC+1 Wolfgang Bangerth wrote:

>
> > One small issue which I noticed is the way how dealii constructs the 
> > Constraint Matrix has probably changed. In order to illustrate this 
> > thing, I have prepared an example (code along with input attached to the 
> > mail for reference ) where I read a triangulation, Mark PBC Boundary 
> > IDs, add periodicity, mark periodic faces and then print the constraint 
> > matrix info.
> > 
> > For code if compiled with dealii 9.0.1. the output is :
> > 
> > Periodic Constraints info:
> >     0 8:  1
> >     1 9:  1
> >     4 10:  1
> >     5 11:  1
> >     12 16:  1
> >     13 17:  1
> > 
> > Periodic Constraints info:
> >     0 12:  1
> >     1 13:  1
> >     2 14:  1
> >     3 15:  1
> >     8 16:  1
> >     9 17:  1
> > 
> > whereas same code compiled with dealii 9.2.0 and ran with same example 
> > gave the following output:
> > 
> > Periodic Constraints info:
> >     8 0:  1
> >     9 1:  1
> >     10 4:  1
> >     11 5:  1
> >     16 12:  1
> >     17 13:  1
> > 
> > Periodic Constraints info:
> >     12 0:  1
> >     13 1:  1
> >     14 2:  1
> >     15 3:  1
> >     16 8:  1
> >     17 9:  1
> > 
> > The order in which Periodic info is received for plus and and minus 
> > faces has reversed, May I know if this behavior was desired or is just a 
> > bug ?
>
> Aditya:
> The end result of the two should be the same, right? I don't know 
> whether anyone remembers what specific patch changed this, but unless 
> you have concrete reasons to believe that one way is correct and the 
> other is wrong, it seems to me that it doesn't matter which way around 
> constraints are built.
>
> Or maybe I don't quite understand why you worry about the change?
>
> Best
> W.
>
> -- 
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> www: http://www.math.colostate.edu/~bangerth/
>

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