[QE-users] DFPT getting stuck [MPI_ERR_TRUNCATE]

[Paolo Giannozzi]

If I understand correctly, you are parallelizing over k points with 32
processors, but you have just 20 k points. As a consequence, in all loops
over k-points, 12 processors will do nothing. While I am quite sure that
such a wasteful parallelization works anyway for the self-consistent code,
I am not equally sure it will for the phonon code. It isn't presumably
difficult to fix it, but I would move to a more sensible parallelization.
For 20 k points and 32 processors, I would try 4 pools of 8 processors
(mpirun -np 32
 ph.x -nk 4 ...)
Paolo

On Tue, May 19, 2020 at 2:12 PM M.J. Hutcheon <mjh261 at cam.ac.uk> wrote:

> Dear QE users/developers,
>
> Following from the previous request, I've changed to a newer MPI library
> which gives a little more error information, specifically it does now crash
> with the following message:
>
> An error occurred in MPI_Allreduce
> eported by process [1564540929,0]
> on communicator MPI COMMUNICATOR 6 SPLIT FROM 3
> MPI_ERR_TRUNCATE: message truncated
> MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, and
> potentially your MPI job)
>
> It appears that this is thrown at the end of a self-consistent DFPT
> calculation (see the attached output file - it appears the final iteration
> has converged). I'm using the development version of QE, so I suspect that
> the error arises from somewhere inside
> https://gitlab.com/QEF/q-e/-/blob/develop/PHonon/PH/solve_linter.f90.
>
> I don't really know how to debug/workaround this further, any
> ideas/suggestions would be most welcome.
>
> Best,
>
> Michael Hutcheon
>
> TCM group, University of Cambridge
>
>
>
> On 2020-05-12 13:29, M.J. Hutcheon wrote:
>
> Dear QE users/developers,
>
> I am running an electron-phonon coupling calculation at the gamma point
> for a large unit cell Calcium-Hydride (Output file attached). The
> calculation appears to get stuck during the DFPT stage. It does not crash,
> or produce any error files/output of any sort, or run out of walltime, but
> the calculation does not progress either. I have tried different parameter
> sets (k-point grids + cutoffs), which changes the representation where the
> calculation gets stuck, but it still gets stuck. I don't really know what
> to try next, short of compiling QE in debug mode and running under a
> debugger to see where it gets stuck. Any ideas before I head down this
> laborious route?
>
> Many thanks,
>
> Michael Hutcheon
>
> TCM group, University of Cambridge
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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