[Trilinos-Users] row/col question re Epetra_FECrsMatrix::SumIntoGlobalValues

Williams, Alan B william at sandia.gov
Tue Aug 9 14:22:41 MDT 2011


ok, I see what you mean. I just looked at the SerialDenseMatrix object, and the documentation for the (i,j) operator isn't real clear. The SerialDenseMatrix object lays data out in the flat array in a manner consistent with fortran ordering. So the (i,j) operator does an implicit transpose when accessing or storing data.
Alan



> -----Original Message-----
> From: Neil N. Carlson [mailto:nnc at lanl.gov]
> Sent: Tuesday, August 09, 2011 2:10 PM
> To: Williams, Alan B
> Cc: trilinos-users at software.sandia.gov
> Subject: RE: [Trilinos-Users] row/col question re
> Epetra_FECrsMatrix::SumIntoGlobalValues
> 
> On Tue, 2011-08-09 at 19:46 +0000, Williams, Alan B wrote:
> > The SerialDenseMatrix object internally contains its data in a flat
> 1-D array. It can be interpreted as a column-major (i.e. fortran
> ordering) or a row-major array depending on how the last argument
> 'format' is specified.
> 
> I guess the issue is that I'm not directly inserting the data into the
> SerialDenseMatrix object's flat array, but using the () operator.  For
> (i,j) the documentation describes i as being the row and j being the
> column -- how the value is stored internally is opaque.  I see no
> options to SerialDenseMatrix constructors that indicate a preference
> for internal format.
> 
> -Neil
> 




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