Error when solving eqns with PETSc

[Ben Tay]

Hi,

I am currently using the following way to solve my poisson eqn

in global.F (global variables)

implicit none

save

Mat    A_mat
Vec    xx,b_rhs
KSP   ksp
PC    pc
PCType      ptype
KSPType        ksptype

then they are initialized

call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
call 
MatCreateSeqAIJ(PETSC_COMM_SELF,size_x*size_y,size_x*size_y,13,PETSC_NULL_INTEGER,A_mat,ierr)
call VecCreateSeq(PETSC_COMM_SELF,size_x*size_y,b_rhs,ierr)
call VecDuplicate(b_rhs,xx,ierr)
call KSPCreate(PETSC_COMM_SELF,ksp,ierr)
call VecAssemblyBegin(b_rhs,ierr)
call VecAssemblyEnd(b_rhs,ierr)
call VecAssemblyBegin(xx,ierr)
call VecAssemblyEnd(xx,ierr)

My original matrix is stored as ITPACK format so I used ellcsr from 
SPARSKIT to convert to CSR format and use

call 
ellcsr(total_k,big_A,int_a,total_k,13,A_spar,ja_spar,ia_spar,nzmax,ierr)
...
call 
MatCreateSeqAIJWithArrays(PETSC_COMM_SELF,Ntot,Ntot,ia_spar,ja_spar,A_spar,A_mat,ierr)
call MatAssemblyBegin(A_mat,MAT_FINAL_ASSEMBLY,ierr)
call MatAssemblyEnd(A_mat,MAT_FINAL_ASSEMBLY,ierr)

to read into PETSc. Then read in the RHS as well

do k=1,Ntot
    II=k-1
    call VecSetValue(b_rhs,II,q_p(k),INSERT_VALUES,ierr)
end do

Finally the matrix is solved using

call KSPSolve(ksp,b_rhs,xx,ierr).

This works but the A_mat matrix is not changing with time. Hence I tried 
to call the above sentences only at the 1st time step. However I got 
this error when KSPSolve is called:

[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, 
probably memory 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/troubleshooting.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: configure using --with-debugging=yes, recompile, link, 
and run
[0]PETSC ERROR: to get more information on the crash.
[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[0]PETSC ERROR: Signal received!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 2.3.3, Patch 4, Tue Aug  7 
17:36:16 CDT 2007 HG revision: ee49636ddd90fb72d14b79fa8180225eb4257c59
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: ./a.out on a atlas3 named atlas3-c01 by g0306332 Tue Aug 
14 18:13:09 2007
[0]PETSC ERROR: Libraries linked from 
/lsftmp/g0306332/petsc-2.3.3-p4/lib/atlas3
[0]PETSC ERROR: Configure run at Sat Aug 11 08:25:45 2007
[0]PETSC ERROR: Configure options --with-cc=icc --with-fc=ifort 
--with-x=0 --download-hypre=1 --download-mumps=1 --download-scalapack=1 
--download-blacs=1 --with-debugging=0 
--with-blas-lapack-dir=/opt/intel/cmkl/8.1.1/ --with-shared 
--with-mpi-dir=/lsftmp/g0306332/mpich2/
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: User provided function() line 0 in unknown directory 
unknown file
[unset]: aborting job:
application called MPI_Abort(MPI_COMM_WORLD, 59) - process 0

I thought I've delcared A_mat as a global variable so after filling up 
values using MatCreateSeqAIJWithArrays, MatAssemblyBegin, 
MatAssemblyEnd, I only need to update the RHS vector. It seems that I'm 
missing out something.