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

[Manuel Valera]

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, 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
>>
>
>
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