[QE-users] DFPT getting stuck [MPI_ERR_TRUNCATE]

[M.J. Hutcheon]

Dear Lorenzo,

> I'm quite sure that the pw code stops if you try to run with more pools than k-points !

This doesn't seem to be the case? I ran a vc-relax and an scf (attached
output) with these (terrible) parallelism settings, and they ran just
fine. 

Best, 

Michael 

On 2020-05-20 09:25, Lorenzo Paulatto wrote:

>> While I am quite sure that such a wasteful parallelization works anyway for the self-consistent code,
> 
> I'm quite sure that the pw code stops if you try to run with more pools than k-points !
> 
>> I am not equally sure it will for the phonon code.
> 
> If the ph code does not stop in this case, I'm confident it will not work properly!
> 
> cheers
> 
> 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 <mailto: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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