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

Williams, Alan B william at sandia.gov
Tue Aug 9 13:46:32 MDT 2011

Hi Neil,

The indices in the IntSerialDenseVector object are used for the global row and column indices.
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.


> -----Original Message-----
> From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-
> users-bounces at software.sandia.gov] On Behalf Of Neil N. Carlson
> Sent: Tuesday, August 09, 2011 1:30 PM
> To: trilinos-users at software.sandia.gov
> Subject: [Trilinos-Users] row/col question re
> Epetra_FECrsMatrix::SumIntoGlobalValues
> For the particular version of Epetra_FECrsMatrix::SumIntoGlobalValues
> that takes a Epetra_IntSerialDenseVector for the indices and a
> Epetra_SerialDenseMatrix for the submatrix of coefficients, I'm
> wondering how the values in the matrix, call it A, are used by the
> method.  Is it indeed the case that the value A(i,j) is destined
> to the element in the ith row (after mapping it through the
> indices vector) and jth col of the FECrsMatrix?  I'm concerned
> about a possible row/col swap (ala Fortran vs C index ordering)
> misunderstanding on my part.
> Thanks,
>   Neil
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