[Trilinos-Users] Questions about Tpetra::RowMatrixTransposer

[Hoemmen, Mark]

(1) You don’t have to provide any parameters.
(2) It looks like you answered the question yourself ( 

mfh

On 3/26/18, 5:27 PM, "Trilinos-Users on behalf of trilinos-users-request at trilinos.org" <trilinos-users-bounces at trilinos.org on behalf of trilinos-users-request at trilinos.org> wrote:

Message: 14
    Date: Fri, 23 Mar 2018 19:15:30 -0400
    From: Wen Yan <wenyan4work at gmail.com>
    To: "trilinos-users at trilinos.org" <trilinos-users at trilinos.org>
    Subject: [Trilinos-Users] Fwd: Questions about
    	Tpetra::RowMatrixTransposer
    Message-ID: <46C3CDC2-6166-4C8F-A97E-6DF6D10CA66F at gmail.com>
    Content-Type: text/plain; charset="us-ascii"
    
    Dear Trilinos user,
    
    I have some questions about the usage and performance of RowMatrixTransposer in Tpetra, which is documented here:
    https://trilinos.org/docs/dev/packages/tpetra/doc/html/classTpetra_1_1RowMatrixTransposer.html <https://trilinos.org/docs/dev/packages/tpetra/doc/html/classTpetra_1_1RowMatrixTransposer.html>
    
    1. The function createTranspose() accepts a parameterList, but what parameters are we supposed to provide?
    
    2. If I have a Tpetra::CrsMatrix (millions of lines and rows, both distributed through mpi, but at maximum 12 nnz per row, very sparse) F, which I need to perform spmv on vectors x and y with both F x and F^T y hundreds of times, should I first explicitly create the transposed CrsMatrix B=F^T with the above Transposer and then do Fx and By? 
    Now I am using the member function apply(,,Teuchos:TRANS) to compute F^T y, and this takes about 3x more time compared to the non-transposed spmv F x.