Dear gdb group: I am a new user of gdb. I have a stupid problems. When I set breakpoint in my program, it seems that I can only set at the function. When I set in a line of my code, it won't stop.For example, I can set the break point at MatGetOwnershipRange(by break MatGetOwnershipRange), but if I want to stop at do 10, II=Istart+1,Iend by (break do 10, II=Istart+1,Iend), it won't stop there. i1 = 1 m = NN n = NN five = 27 call PetscOptionsGetInt(PETSC_NULL_CHARACTER,'-m',m,flg,ierr) call PetscOptionsGetInt(PETSC_NULL_CHARACTER,'-n',n,flg,ierr) call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr) call MatCreate(PETSC_COMM_WORLD,A,ierr) call MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n,ierr) call MatSetType(A, MATAIJ,ierr) call MatSetFromOptions(A,ierr) call MatMPIAIJSetPreallocation(A,five,PETSC_NULL_INTEGER,five, & & PETSC_NULL_INTEGER,ierr) call MatSeqAIJSetPreallocation(A,five,PETSC_NULL_INTEGER,ierr) call MatGetOwnershipRange(A,Istart,Iend,ierr) do 10, II=Istart+1,Iend ROW_NUM=SPAI(II+1)-SPAI(II) ALLOCATE(NCOL_PERROW(ROW_NUM),VALUE_PERROW(ROW_NUM)) KVAL_START=SPAI(II) KVAL_END=SPAI(II+1)-1 NCOL_PERROW=SPAJ(KVAL_START:KVAL_END) VALUE_PERROW=SPAA(KVAL_START:KVAL_END) call MatSetValues(A,i1,II-1,ROW_NUM,NCOL_PERROW,VALUE_PERROW,INSERT_VALUES,ierr) DEALLOCATE(NCOL_PERROW,VALUE_PERROW) 10 continue Another problem is that when I stop at MatGetOwnershipRange, I want to see the value of i1 by print i1, it shows No symbol "i1" in current context.