[Trilinos-Users] trace of CrsMatrix

[Heroux, Mike]

The following function will compute the matrix trace of any Epetra_RowMatrix (including Epetra_CrsMatrix):

double MatrixTrace(const Epetra_RowMatrix & A) {

    Epetra_Vector diagA(A.RowMatrixRowMap());
    A.ExtractDiagonalCopy(diagA);
    double localTrace = 0.0, globalTrace = 0.0;
    for (int i=0; i<A.NumMyRows(); i++) localTrace += diagA[i];
    A.RowMatrixRowMap().Comm().SumAll(&localTrace, &globalTrace, 1);

  return globalTrace;

}

Mike

From: Sunghwan Choi <sunghwanchoi91 at gmail.com<mailto:sunghwanchoi91 at gmail.com>>
Date: Saturday, April 6, 2013 7:40 AM
To: "trilinos-users at software.sandia.gov<mailto:trilinos-users at software.sandia.gov>" <trilinos-users at software.sandia.gov<mailto:trilinos-users at software.sandia.gov>>
Subject: [Trilinos-Users] trace of CrsMatrix

Hi,
I want to find the way to sum diagonal values of CrsMatrix; trace of CrsMatrix.
I thought several ways but I prefer combination of internal method because I don’t want to spend my time to make my code parallelized.
Is there any good way to do that?

Sunghwan Choi