Conversion matrix from Ellpack-Itpack to CSR to PETSc format

[Ben Tay]

Hi,

My original matrix is stored in Ellpack-Itpack format, which is used by 
the NSPCG solver. I have problems when I insert the values of the matrix 
into a PETSc matrix. I guessed I made some mistakes but I can't find 
where during debugging. So I intent to just convert from the 
Ellpack-Itpack to CSR using a subroutine by SPARSKIT2 called ellcsr. 
Then I use MatCreateSeqAIJWithArrays to get my PETSc matrix.
I'm programming in fortran so index starts from 1. I tried to shift the 
row and column index by -1.  The 1st step works but there's error when 
solving at the 2nd time step. The error is:

[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, 
probably m
emory access out of range
[0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
[0]PETSC ERROR: or see 
http://www.mcs.anl.gov/petsc/petsc-as/documentation/troub
leshooting.html#Signal[0]PETSC ERROR: or try http://valgrind.org on 
linux or man
 libgmalloc on Apple to find memory corruption errors
[0]PETSC ERROR: likely location of problem given in stack below
[0]PETSC ERROR: ---------------------  Stack Frames 
----------------------------
--------
[0]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
[0]PETSC ERROR:       INSTEAD the line number of the start of the function
[0]PETSC ERROR:       is given.




My subroutine is as follows:

Note that A_mat is declared as global variable.

if (time==1) then

    call 
ellcsr(total_k,big_A,int_a,total_k,9,A_spar,ja_spar,ia_spar,nzmax,ierr)   
-   convert big_A,int_A in Ellpack-Itpack format to CSR using ellcsr

    ia_spar=ia_spar-1;    ja_spar=ja_spar-1   -   shift by -1

    call 
MatCreateSeqAIJWithArrays(PETSC_COMM_SELF,Ntot,13,ia_spar,ja_spar,A_spar,A_mat_spar,ierr)

    call MatAssemblyBegin(A_mat,MAT_FINAL_ASSEMBLY,ierr)

    call MatAssemblyEnd(A_mat,MAT_FINAL_ASSEMBLY,ierr)

end if

...

I thought I would only need to do this once since the A_mat does not 
change and it is declared globally. If I remove the "IF - END IF" and 
execute at every time step, everything will be fine. But I thought that 
will be very inefficient. So how should I solve the problem?

Thanks