[Trilinos-Users] problems with ReplaceGlobalValues

[Williams, Alan B]

Riccardo,

When GlobalAssemble gathers the matrix data from the overlapping distribution to the non-overlapping distribution, there isn't an easy way for it to figure out which value 'wins' for terms that come from multiple processors. For example if proc 1 set element (10,12) to a value of 5, and proc 2 sets the same element to a value of 7, what should the value be in the assembled matrix? What does 'replace' mean in that case? The most common usage for finite-element assemblies is to add them, so that's what we've chosen to do. Let us know if a different option would make sense for your scenario.

Alan


> -----Original Message-----
> From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-
> users-bounces at software.sandia.gov] On Behalf Of Riccardo Rossi
> Sent: Thursday, February 03, 2011 3:34 AM
> To: trilinos-users at software.sandia.gov
> Subject: [Trilinos-Users] problems with ReplaceGlobalValues
> 
> Dear list,
> 
>      i am experiencing problems using Epetra_FECrsMatrix and
> ReplaceGlobalValues
> 
> i attach a minimal script where i fill up a 4*4 FEcrs matrix on
> 2processors, i set it to zero and then i try to replace the global
> values.
> 
> processor 1 sets all of its elements to 10
> processor 2 sets all to 20
> 
> ...after GlobalAssemble i get that some terms have a value of 30!! that
> is...values are not replaced but rather added.
> The output is also attached
> 
> at this point i am really stuck ... please help
> 
> Riccardo
> 
> 
> 
> --
> ________________________________________________________________
> Riccardo Rossi, Ph.D, Civil Engineer
> member of the Kratos Group: kratos.cimne.upc.es
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