[petsc-users] Best way to scatter a Seq vector ?
Dave May
dave.mayhem23 at gmail.com
Fri Jan 6 14:44:54 CST 2017
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,l
>> ocis,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
>> >
>> >
>>
>>
>
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