[petsc-users] Best way to scatter a Seq vector ?

[Barry Smith]

   Take the scatter out of the if () since everyone does it and get rid of the VecView(). 

   Does this work? If not where is it hanging?


> On Jan 6, 2017, at 3:29 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> 
> Thanks Dave,
> 
> I think is interesting it never gave an error on this, after adding the vecassembly calls it still shows the same behavior, without complaining, i did:
> 
> if(rankl==0)then
> 
>      call VecSetValues(bp0,nbdp,ind,Rhs,INSERT_VALUES,ierr)
>      call VecAssemblyBegin(bp0,ierr) ; call VecAssemblyEnd(bp0,ierr);
>      CHKERRQ(ierr)
> 
endif
> 
> 
>      call VecScatterBegin(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr)
>      call VecScatterEnd(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr)
>      print*,"done! "
>      CHKERRQ(ierr)
> 
> 
>        CHKERRQ(ierr)
> 
> 
> Thanks.
> 
> On Fri, Jan 6, 2017 at 12:44 PM, Dave May <dave.mayhem23 at gmail.com> wrote:
> 
> 
> On 6 January 2017 at 20:24, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> Great help Barry, i totally had overlooked that option (it is explicit in the vecscatterbegin call help page but not in vecscattercreatetozero, as i read later)
> 
> So i used that and it works partially, it scatters te values assigned in root but not the rest, if i call vecscatterbegin from outside root it hangs, the code currently look as this:
> 
>   call VecScatterCreateToZero(bp2,ctr,bp0,ierr); CHKERRQ(ierr)
> 
>   call PetscObjectSetName(bp0, 'bp0:',ierr)
> 
> if(rankl==0)then
> 
>      call VecSetValues(bp0,nbdp,ind,Rhs,INSERT_VALUES,ierr)
> 
>      call VecView(bp0,PETSC_VIEWER_STDOUT_WORLD,ierr)
> 
> 
> You need to call
> 
>   VecAssemblyBegin(bp0);
>   VecAssemblyEnd(bp0);
> after your last call to VecSetValues() before you can do any operations with bp0.
> 
> With your current code, the call to VecView should produce an error if you used the error checking macro CHKERRQ(ierr) (as should VecScatter{Begin,End}
> 
> Thanks,
>   Dave
>  
> 
>      call VecScatterBegin(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr)
>      call VecScatterEnd(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr) 
>      print*,"done! "
>      CHKERRQ(ierr)
> 
> endif
> 
>    ! call VecScatterBegin(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr)
>    !  call VecScatterEnd(ctr,bp0,bp2,INSERT_VALUES,SCATTER_REVERSE,ierr)
> 
>   call VecView(bp2,PETSC_VIEWER_STDOUT_WORLD,ierr)
> 
>   call PetscBarrier(PETSC_NULL_OBJECT,ierr)
>   
>   call exit()
> 
> 
> 
> And the output is: (with bp the right answer)
> 
> Vec Object:bp: 2 MPI processes
>   type: mpi
> Process [0]
> 1.
> 2.
> Process [1]
> 4.
> 3.
> Vec Object:bp2: 2 MPI processes  (before scatter)
>   type: mpi
> Process [0]
> 0.
> 0.
> Process [1]
> 0.
> 0.
> Vec Object:bp0: 1 MPI processes
>   type: seq
> 1.
> 2.
> 4.
> 3.
>  done! 
> Vec Object:bp2: 2 MPI processes  (after scatter)
>   type: mpi
> Process [0]
> 1.
> 2.
> Process [1]
> 0.
> 0.
> 
> 
> 
> 
> Thanks inmensely for your help,
> 
> Manuel
> 
> 
> On Thu, Jan 5, 2017 at 4:39 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> > On Jan 5, 2017, at 6:21 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> >
> > Hello Devs is me again,
> >
> > I'm trying to distribute a vector to all called processes, the vector would be originally in root as a sequential vector and i would like to scatter it, what would the best call to do this ?
> >
> > I already know how to gather a distributed vector to root with VecScatterCreateToZero, this would be the inverse operation,
> 
>    Use the same VecScatter object but with SCATTER_REVERSE, not you need to reverse the two vector arguments as well.
> 
> 
> > i'm currently trying with VecScatterCreate() and as of now im doing the following:
> >
> >
> > if(rank==0)then
> >
> >
> >      call VecCreate(PETSC_COMM_SELF,bp0,ierr); CHKERRQ(ierr) !if i use WORLD
> >                                                              !freezes in SetSizes
> >      call VecSetSizes(bp0,PETSC_DECIDE,nbdp,ierr); CHKERRQ(ierr)
> >      call VecSetType(bp0,VECSEQ,ierr)
> >      call VecSetFromOptions(bp0,ierr); CHKERRQ(ierr)
> >
> >
> >      call VecSetValues(bp0,nbdp,ind,Rhs,INSERT_VALUES,ierr)
> >
> >      !call VecSet(bp0,5.0D0,ierr); CHKERRQ(ierr)
> >
> >
> >      call VecView(bp0,PETSC_VIEWER_STDOUT_WORLD,ierr)
> >
> >      call VecAssemblyBegin(bp0,ierr) ; call VecAssemblyEnd(bp0,ierr) !rhs
> >
> >      do i=0,nbdp-1,1
> >         ind(i+1) = i
> >      enddo
> >
> >      call ISCreateGeneral(PETSC_COMM_SELF,nbdp,ind,PETSC_COPY_VALUES,locis,ierr)
> >
> >     !call VecScatterCreate(bp0,PETSC_NULL_OBJECT,bp2,is,ctr,ierr) !if i use SELF
> >                                                                   !freezes here.
> >
> >      call VecScatterCreate(bp0,locis,bp2,PETSC_NULL_OBJECT,ctr,ierr)
> >
> > endif
> >
> > bp2 being the receptor MPI vector to scatter to
> >
> > But it freezes in VecScatterCreate when trying to use more than one processor, what would be a better approach ?
> >
> >
> > Thanks once again,
> >
> > Manuel
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Wed, Jan 4, 2017 at 3:30 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> > Thanks i had no idea how to debug and read those logs, that solved this issue at least (i was sending a message from root to everyone else, but trying to catch from everyone else including root)
> >
> > Until next time, many thanks,
> >
> > Manuel
> >
> > On Wed, Jan 4, 2017 at 3:23 PM, Matthew Knepley <knepley at gmail.com> wrote:
> > On Wed, Jan 4, 2017 at 5:21 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> > I did a PetscBarrier just before calling the vicariate routine and im pretty sure im calling it from every processor, code looks like this:
> >
> > From the gdb trace.
> >
> >   Proc 0: Is in some MPI routine you call yourself, line 113
> >
> >   Proc 1: Is in VecCreate(), line 130
> >
> > You need to fix your communication code.
> >
> >    Matt
> >
> > call PetscBarrier(PETSC_NULL_OBJECT,ierr)
> >
> > print*,'entering POInit from',rank
> > !call exit()
> >
> > call PetscObjsInit()
> >
> >
> > And output gives:
> >
> >  entering POInit from           0
> >  entering POInit from           1
> >  entering POInit from           2
> >  entering POInit from           3
> >
> >
> > Still hangs in the same way,
> >
> > Thanks,
> >
> > Manuel
> >
> >
> >
> > On Wed, Jan 4, 2017 at 2:55 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> > Thanks for the answers !
> >
> > heres the screenshot of what i got from bt in gdb (great hint in how to debug in petsc, didn't know that)
> >
> > I don't really know what to look at here,
> >
> > Thanks,
> >
> > Manuel
> >
> > On Wed, Jan 4, 2017 at 2:39 PM, Dave May <dave.mayhem23 at gmail.com> wrote:
> > Are you certain ALL ranks in PETSC_COMM_WORLD call these function(s). These functions cannot be inside if statements like
> > if (rank == 0){
> >   VecCreateMPI(...)
> > }
> >
> >
> > On Wed, 4 Jan 2017 at 23:34, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> > Thanks Dave for the quick answer, appreciate it,
> >
> > I just tried that and it didn't make a difference, any other suggestions ?
> >
> > Thanks,
> > Manuel
> >
> > On Wed, Jan 4, 2017 at 2:29 PM, Dave May <dave.mayhem23 at gmail.com> wrote:
> > You need to swap the order of your function calls.
> > Call VecSetSizes() before VecSetType()
> >
> > Thanks,
> >   Dave
> >
> >
> > On Wed, 4 Jan 2017 at 23:21, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> > Hello all, happy new year,
> >
> > I'm working on parallelizing my code, it worked and provided some results when i just called more than one processor, but created artifacts because i didn't need one image of the whole program in each processor, conflicting with each other.
> >
> > Since the pressure solver is the main part i need in parallel im chosing mpi to run everything in root processor until its time to solve for pressure, at this point im trying to create a distributed vector using either
> >
> >      call VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,nbdp,xp,ierr)
> > or
> >      call VecCreate(PETSC_COMM_WORLD,xp,ierr); CHKERRQ(ierr)
> >      call VecSetType(xp,VECMPI,ierr)
> >      call VecSetSizes(xp,PETSC_DECIDE,nbdp,ierr); CHKERRQ(ierr)
> >
> >
> > In both cases program hangs at this point, something it never happened on the naive way i described before. I've made sure the global size, nbdp, is the same in every processor. What can be wrong?
> >
> > Thanks for your kind help,
> >
> > Manuel.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> > -- Norbert Wiener
> >
> >
> 
> 
> 
>