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
