On all processors, the array you get is indexed: xx_v(1:(Iend-Istart))
while the Istart and Iend are global indices into the global Vec. It's only by luck that the values on proc 3 are correct (this code should probably seg fault as it is accessing memory outside of the bounds of xx_v). To access the array, you'll want: do i=1, (Iend-Istart) write(6,*)'check xx_v',i,xx_v(i),myid enddo or (better yet) pass it into a subroutine to get the array indexed correctly, like demonstrated in the example. Ethan On Wed, 2011-01-05 at 11:23 -0600, Peter Wang wrote: > Thanks, Satish, > > The index of the array is modified to i+1: > !=================== > do i=Istart,Iend-1 > write(6,*)'check xx_v',i+1,xx_v(i+1),myid > enddo > !=================== > > However, only the elements on root process (process 0) and the > last process (process 3) are corrent, is there any ohter logical > error? > > check xx_v 1 3999.9999999999982 0 > check xx_v 2 3999.9999999999982 0 > check xx_v 3 3999.9999999999982 0 > check xx_v 4 3999.9999999999982 0 > check xx_v 5 3999.9999999999982 0 > check xx_v 6 3000.0000000000005 0 > check xx_v 7 3000.0000000000005 0 > check xx_v 8 2.61360726650019422E-321 1 > check xx_v 9 7.90505033345994471E-323 1 > check xx_v 10 1.69759663277221785E-312 1 > check xx_v 11 6.16840020108069212E-317 1 > check xx_v 12 6.16840316547456717E-317 1 > check xx_v 13 6.16832658529946177E-317 1 > check xx_v 14 1.99665037664579820E-314 2 > check xx_v 15 6.19784009071943448E-317 2 > check xx_v 16 6.20249221284067566E-317 2 > check xx_v 17 6.20218737433719161E-317 2 > check xx_v 18 6.18236051996958238E-317 2 > check xx_v 19 6.16840316547456717E-317 2 > check xx_v 20 6.18107199676522841E-317 3 > check xx_v 21 0.0000000000000000 3 > check xx_v 22 0.0000000000000000 3 > check xx_v 23 0.0000000000000000 3 > check xx_v 24 0.0000000000000000 3 > check xx_v 25 0.0000000000000000 3 > > > > > Date: Tue, 4 Jan 2011 22:49:50 -0600 > > From: balay at mcs.anl.gov > > To: petsc-users at mcs.anl.gov > > Subject: Re: [petsc-users] error in calling VecGetArrayf90() > > > > The global index starts at Istart - but the array index starts at 1 > [for fortran array] > > > > Satish > > > > On Tue, 4 Jan 2011, Peter Wang wrote: > > > > > > > > In last question, the pointer xx_v is local data. However, if > write them to the monitor or assign them to another array, the value > is incorrect. > > > > > > The protion of the code to display them on the monitor is like as > following: > > > call MatGetOwnershipRange(A,Istart,Iend,ierr) > > > call VecGetArrayF90(x,xx_v,ierr) ! Vector x is matched with Matrix > A in the same communicator > > > > > > write(*,*)xx_v,myid ! write the poiner array together > > > > > > do i=Istart,Iend-1 > > > write(6,*)'check xx_v',i,xx_v(i),myid !write the element of the > array one by one with local range (Istart to Iend-1) > > > enddo > > > > > > > > > =========The result is as following: ( the values of the elements > from 7 to 20 are not correct !!) > > > > > > 3999.9999999999982 3999.9999999999982 3999.9999999999982 > 3999.9999999999982 3999.9999999999982 3000.0000000000005 > 3000.0000000000005 0 > > > > > > 3000.0000000000009 3000.0000000000009 3000.0000000000009 > 2000.0000000000011 2000.0000000000011 2000.0000000000000 1 > > > > > > 2000.0000000000009 2000.0000000000009 1000.0000000000003 > 1000.0000000000003 1000.0000000000003 999.99999999999989 2 > > > > > > 1000.0000000000000 0.0000000000000000 0.0000000000000000 > 0.0000000000000000 0.0000000000000000 0.0000000000000000 3 > > > > > > > > > check xx_v 0 0.0000000000000000 0.0000000000000000 0 > > > check xx_v 1 3999.9999999999982 3999.9999999999982 0 > > > check xx_v 2 3999.9999999999982 3999.9999999999982 0 > > > check xx_v 3 3999.9999999999982 3999.9999999999982 0 > > > check xx_v 4 3999.9999999999982 3999.9999999999982 0 > > > check xx_v 5 3999.9999999999982 3999.9999999999982 0 > > > check xx_v 6 3000.0000000000005 3000.0000000000005 0 > > > check xx_v 7 1.99665037664579820E-314 1.99665037664579820E-314 1 > > > check xx_v 8 2.61360726650019422E-321 2.61360726650019422E-321 1 > > > check xx_v 9 7.90505033345994471E-323 7.90505033345994471E-323 1 > > > check xx_v 10 1.69759663277221785E-312 1.69759663277221785E-312 1 > > > check xx_v 11 6.16846344148335980E-317 6.16846344148335980E-317 1 > > > check xx_v 12 6.16846640587723485E-317 6.16846640587723485E-317 1 > > > check xx_v 13 6.16838982570212945E-317 6.16838982570212945E-317 2 > > > check xx_v 14 1.99665037664579820E-314 1.99665037664579820E-314 2 > > > check xx_v 15 6.19790333112210216E-317 6.19790333112210216E-317 2 > > > check xx_v 16 6.20255545324334334E-317 6.20255545324334334E-317 2 > > > check xx_v 17 6.20225061473985929E-317 6.20225061473985929E-317 2 > > > check xx_v 18 6.18242376037225006E-317 6.18242376037225006E-317 2 > > > check xx_v 19 6.16846640587723485E-317 6.16846640587723485E-317 3 > > > check xx_v 20 6.18113523716789609E-317 6.18113523716789609E-317 3 > > > check xx_v 21 0.0000000000000000 0.0000000000000000 3 > > > check xx_v 22 0.0000000000000000 0.0000000000000000 3 > > > check xx_v 23 0.0000000000000000 0.0000000000000000 3 > > > check xx_v 24 0.0000000000000000 0.0000000000000000 3 > > > > > > ======The vector x is : > > > Process [0] > > > 4000 > > > 4000 > > > 4000 > > > 4000 > > > 4000 > > > 3000 > > > 3000 > > > Process [1] > > > 3000 > > > 3000 > > > 3000 > > > 2000 > > > 2000 > > > 2000 > > > Process [2] > > > 2000 > > > 2000 > > > 1000 > > > 1000 > > > 1000 > > > 1000 > > > Process [3] > > > 1000 > > > 0 > > > 0 > > > 0 > > > 0 > > > 0 > > > > > > > > > > > > > > > > Date: Tue, 4 Jan 2011 17:50:11 -0600 > > > > From: balay at mcs.anl.gov > > > > To: petsc-users at mcs.anl.gov > > > > Subject: Re: [petsc-users] error in calling VecGetArrayf90() > > > > > > > > Did you included "finclude/petscvec.h90" in your code - as the > example did? > > > > > > > > satish > > > > > > > > On Tue, 4 Jan 2011, Peter Wang wrote: > > > > > > > > > > > > > > I am trying to obtain the value of each element of a solution > Vector by KSPsolve(). > > > > > > > > > > The variables are defined according the example of ex4f90.F in > \petsc-3.1-p5\src\snes\examples\tutorials\ as following, > > > > > > > > > > PetscScalar, pointer :: xx_v(:) > > > > > > > > > > ... > > > > > call KSPSolve(ksp,b,x,ierr) > > > > > call VecView(x,PETSC_VIEWER_STDOUT_WORLD,ierr) > > > > > > > > > > call VecGetArrayF90(x,xx_v,ierr) > > > > > call VecRestoreArrayF90(x,xx_v,ierr) > > > > > > > > > > ... > > > > > > > > > > But, the error keeps coming out when call > VecGetArrayF90(x,xx_v,ierr) and call VecRestoreArrayF90(x,xx_v,ierr) > are not commented off. > > > > > > > > > > > > > > > The error information shows: > > > > > Caught signal number 11 SEGV: Segmentation Violation, probably > memory access out of range > > > > > > > > > > [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. > > > > > [0]PETSC ERROR: [0] F90Array1dCreate line 52 > src/sys/f90-src/f90_cwrap.c > > > > > [0]PETSC ERROR: --------------------- Error Message > ------------------------------------ > > > > > > > > > > I checked the code according the example, but cannot see any > difference to that. Just don't know why the pointer array xx_v doesn't > work here? Thanks. > > > > > > > > > > > > > > > > > > > -- ------------------------------------- Ethan Coon Post-Doctoral Researcher Mathematical Modeling and Analysis Los Alamos National Laboratory 505-665-8289 http://www.ldeo.columbia.edu/~ecoon/ -------------------------------------
