[Trilinos-Users] Fwd: Questions about Tpetra::RowMatrixTransposer

Wen Yan wenyan4work at gmail.com
Fri Mar 23 19:15:30 EDT 2018

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.

Thank you,
Wen Yan

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