[Trilinos-Users] Tpetra example compilation error

[Martin Vymazal]

Hello Mark,

 thank you for the clarification.

Best regards,

 Martin Vymazal

On Thursday 13 of November 2014 19:18:32 Hoemmen, Mark wrote:
> On 11/13/14, 12:00 PM, "trilinos-users-request at software.sandia.gov"
> 
> <trilinos-users-request at software.sandia.gov> wrote:
> >Message: 1
> >Date: Thu, 13 Nov 2014 00:35:56 +0100
> >From: Martin Vymazal <martin.vymazal at vki.ac.be>
> >To: trilinos-users at software.sandia.gov
> >Subject: [Trilinos-Users] Tpetra example compilation error
> >Message-ID: <118002104.DGWF7o2v5u at tinlaptop>
> >Content-Type: text/plain; charset="utf-8"
> >
> >Dear Trilinos developers,
> >
> > the example
> > 
> > "Create and use a preconditioner for a sequence of linear systems"
> >
> >from
> >
> >  https://code.google.com/p/trilinos/wiki/Tpetra_Belos_CreateSolver
> >
> >does not compile with local_ordinal_type set to unsigned integer.
> 
> Tpetra does not support unsigned local ordinal types.  You must use a
> signed type there.  Please refer to the Tpetra documentation, in
> particular the documentation of Map's template parameters, for more
> details.
> 
> >Could you explain why is (signed) integer type used for indexing entries
> >in
> >matrices and vectors? I understand that subtracting two unsigned integers
> >can
> >give unexpected results when not handled with care;
> 
> That's the reason.  You should think of local ordinals as an
> implementation detail.  We actually have users who exercise unsigned
> _global_ ordinals, so that case is well tested.  We prefer signed ordinals
> (both local and global) in general.
> 
> mfh
> 
> 
> 
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