[Q-e-developers] calbec() hungs if # of MPI process > 1

[Paolo Giannozzi]

On Tue, Nov 3, 2015 at 10:16 PM, Ilya Ryabinkin <igryabinkin at gmail.com>
wrote:

>
> I call get_nacs() subroutine from subroutine verlet(), in particular,
> past the line 229 of dynamics_module.f90, if the  matters.
>

it matters. Subroutine verlet is called only by processor 0 ("ionode"), so
if you try to do anything in parallel inside it, it will hang for sure.
What is not parallel is often done on a single processor, results are then
broadcast to the other processors. Why, it is explained in Sec.8.3. of the
developer manual

Paolo

>
> > There isn't anything obviously wrong in your piece of code. Is it inside
> a
> > modified version of pw.x, or is it stand-alone? in the latter case, there
> > might be some missing initialization.
>
> It sounds relevant. Indeed, in extrapolate_wfcs() the very first (as
> well as the very last) line is
>
>   CALL mp_barrier( intra_image_comm ) ! debug
>
> I tried to add these lines to my get_nacs() as well, but it doesn't do
> any good: code hungs immediately, without even going past mp_barrier()
>
> --
> Ilya
>
>
> In the former case...it shouldn't
> > happen. Anyway: try first of all to figure out where your code hangs.
> > "calbec" is an interface to several different routines. Maybe it goes
> into
> > the wrong one. It should just do a call to DGEMM or ZGEMM and a call to
> > mp_sum (wrapper to mpi_reduce)
> >
> > Paolo
> >
> > On Tue, Nov 3, 2015 at 7:47 PM, Ilya Ryabinkin <igryabinkin at gmail.com>
> > wrote:
> >>
> >> Dear colleagues:
> >> I'm developing a code to calculate the non-adiabatic couplings using
> >> finite-difference scheme. The problem I currently stumbled upon is the
> >> following:
> >>
> >> I need to calculate the overlap matrix between MOs at t-dt and t,
> >> gamma_only. What  I'm doing:
> >>
> >> Code is borrowed from update_pot.f90, subroutine extrapolate_wfcs(),
> >> lines  595-600
> >>
> >>       ALLOCATE( evcold( npwx, nbnd ), aux( npwx, nbnd ) )
> >>       !! Retreive old WF at t-dt from *.oldwfc file
> >>       CALL davcio( evcold, 2*nwordwfc, iunoldwfc, 1, -1 )
> >>       !! Get current WF at t
> >>       aux = evc
> >>       !
> >>      ALLOCATE( S( nbnd, nbnd ), O( nbnd, nbnd ) )
> >>       CALL calbec( npw, aux, evcold, S ) ! Get overlap S(t-dt, t)
> >>       !
> >>       O = ANINT( S )    ! O is a rounded S matrix to perform phase and
> >>                                 ! ordering matching
> >>       IF ( ANY( diag( O ) == 0.0_dp ) ) THEN
> >>          ...
> >>
> >> Essentially, my code hungs at calbec() call if I ran it in parallell
> >> with # of MPI process >1. gdb shows that processes are in a polling
> >> loop, which means that they are wait for something. I'm baffled at
> >> this point, as there is nothing they should wait for.
> >>
> >> What I am missing?
> >>
> >> Thanks for the help,
> >> Ilya
> >> _______________________________________________
> >> Q-e-developers mailing list
> >> Q-e-developers at qe-forge.org
> >> http://qe-forge.org/mailman/listinfo/q-e-developers
> >
> >
> >
> >
> > --
> > Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> > Phone +39-0432-558216, fax +39-0432-558222
> >
> > _______________________________________________
> > Q-e-developers mailing list
> > Q-e-developers at qe-forge.org
> > http://qe-forge.org/mailman/listinfo/q-e-developers
> >
>
> _______________________________________________
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> http://qe-forge.org/mailman/listinfo/q-e-developers
>
>


-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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