[Wien] lapw0_mpi (MPI_Bcast) bug

[Laurence Marks]

For completeness, I should have written

#ifdef Parallel
     if (.not.coul) allocate(potk(nkk))
     ibbuff=32768  ! Could be optimized
     i2=NKK/ibbuff
     it1=1
     do i=1,i2
       call MPI_Bcast(potk(it1), ibbuff, MPI_DOUBLE_COMPLEX ,
0,MPI_COMM_WORLD , ierr)
       it1=it1+ibbuff
     enddo
     if(it1 .lt. nkk)then
       it2=nkk-it1+1
       call MPI_Bcast(potk(it1), it2, MPI_DOUBLE_COMPLEX ,
0,MPI_COMM_WORLD , ierr)
     endif
     call MPI_BARRIER(MPI_COMM_WORLD,ierr)
#endif

This can probably be improved since I believe that potk is only needed
for meta-functionals, and sending it too all nodes is a little
inefficient

On Wed, Feb 3, 2010 at 6:34 AM, Laurence Marks <L-marks at northwestern.edu> wrote:
> Yes, thanks, that was a typo.
>
> On Wed, Feb 3, 2010 at 2:01 AM, Pawel Lesniak <lesniak at ifmpan.poznan.pl> wrote:
>> W dniu 02.02.2010 20:21, Laurence Marks pisze:
>>>
>>> There is a bug in some mpi implementations that can lead to a SIGSEV
>>> in lapw0_mpi for large problems. The symptom is a SIGSEV at the
>>> MPI_Bcast call
>>> at about line 1574:
>>> #ifdef Parallel
>>>  if (.not.coul)  allocate(potk(nkk))
>>>  call MPI_Bcast(potk, NKK, MPI_DOUBLE_COMPLEX, 0,MPI_COMM_WORLD , ierr)
>>> #endif
>>>
>>> A patch (works) is to not do the MPI_Bcase all at once:
>>>
>>> #ifdef Parallel
>>>       if (.not.coul) allocate(potk(nkk))
>>>       ibbuff=32768  ! Could be optimized
>>>       i2=NKK/ibbuff
>>>       it1=1
>>>       do i=1,i2
>>>         call MPI_Bcast(potk(it1), 1024, MPI_DOUBLE_COMPLEX ,
>>> 0,MPI_COMM_WORLD , ierr)
>>>         it1=it1+ibbuff
>>>       enddo
>>>       if(it1 .lt. nkk)then
>>>         it2=nkk-it1+1
>>>         call MPI_Bcast(potk(it1), it2, MPI_DOUBLE_COMPLEX ,
>>> 0,MPI_COMM_WORLD , ierr)
>>>       endif
>>>       call MPI_BARRIER(MPI_COMM_WORLD,ierr)
>>> #endif
>>>
>>>
>>>
>>
>> Are you sure that
>> call MPI_Bcast(potk(it1), 1024, MPI_DOUBLE_COMPLEX ,
>> 0,MPI_COMM_WORLD , ierr)
>> is correct?
>> Why length of 1024 when you split array by ibbuff ?
>> I believe correct version is:
>> call MPI_Bcast(potk(it1), ibbuff, MPI_DOUBLE_COMPLEX ,
>> 0,MPI_COMM_WORLD , ierr)
>>
>>
>> Pawel Lesniak
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>
>
>
> --
> Laurence Marks
> Department of Materials Science and Engineering
> MSE Rm 2036 Cook Hall
> 2220 N Campus Drive
> Northwestern University
> Evanston, IL 60208, USA
> Tel: (847) 491-3996 Fax: (847) 491-7820
> email: L-marks at northwestern dot edu
> Web: www.numis.northwestern.edu
> Chair, Commission on Electron Crystallography of IUCR
> www.numis.northwestern.edu/
> Electron crystallography is the branch of science that uses electron
> scattering and imaging to study the structure of matter.
>



-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Electron crystallography is the branch of science that uses electron
scattering and imaging to study the structure of matter.