# [Trilinos-Users] ForTrilinos: Problems with Epetra_Vector

Dominic Kedelty dkedelty at asu.edu
Mon Nov 30 15:47:40 EST 2015

```I am having a problem with Epetra_Vectors inside of  ForTrilinos. Currently
I have a parallel CFD code set up that constructs a CRS sparse A matrix and
a B vector for the discretization that I am dealing with. What I would like
to do is have a subroutine that I pass in the row_pointer for a A, column
indices for A, and the B vector and get an X vector as an output.
Initially, what I wanted to do was have A_ B_ and X_ be epetra_crsmatrix
and epetra_vectors that are defined within the scope of a subroutine.

subroutine solve_problem( rowptr_A, colidx_A, values_A, values_B, values_X )
type(Epetra_MpiComm) :: comm
type(Epetra_Map) :: map
type(Epetra_CrsMatrix) :: A_
type(Epetra_Vector) :: X_,B_
type(AztecOO) :: Solver

comm = Epetra_MpiComm(MPI_COMM_WORLD)

map = Epetra_Map(-1_c_int,MyGlobalCVs,1_c_int,comm)

A_ = Epetra_CrsMatrix(FT_Epetra_DataAccess_E_Copy,map,NumNonZero)

[... Fill A ...]

B_=Epetra_Vector(map,.true.)
X_=Epetra_Vector(map,.true.)

[... solve here ...]

call Solver%force_finalize
call X_%force_finalize()
call B_%force_finalize()
call A_%force_finalize()
call map%force_finalize()
call comm%force_finalize()

end subroutine

When I coded this approach, it worked for my first timestep (I verified the
values_X solution and it was correct)... But, for whatever reason, when the
subroutine is called a second time I get random errors (mostly SIGSEGV).
After some debugging, I have found that the problem lies when I call
B_=Epetra_Vector(map,.true.) or any Epetra_Vector for that matter. The
problem does not happen during the call however, it happens when I leave
the subroutine.

I've read that the force_finalize calls are only needed with certain
compilers, is this true? and do I need to call force_finalize. Second, I am
using an arbitrary map for CVs that I have partitioned across multiple
processors. Am I doing anything wrong with how I am declaring my map, or
how I am using it? And is there any information that would be useful in
figuring out why I am having issues with the Epetra Vectors. Thanks.
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