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

[Paolo Giannozzi]

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. 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
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>



-- 
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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