[Pw_forum] Error "Not diagonalizing because representation xx is not done" in "image" parallelization by ph.x
Coiby Xu
coiby.xu at gmail.com
Wed May 4 05:33:28 CEST 2016
Dear Quantum Espresso Developers and Users,
I'm running a phonon calculation parallelizing over the representations/q
vectors. For my cluster, there are 24 cores per node. I want to use as many
nodes as possible to speed up the calculation.
I set the number of parallelizations to be the number of nodes,
> mpirun -np NUMBER_OF_NODESx24 ph.x -nimage NUMBER_OF_NODES
>
If I only use 4 nodes (4 images), 8 nodes ( 8 images), the calculation will
be finished successfully. However, more than 8 nodes, say 16 or 32 nodes,
are used, each time running the calculation, such error will be given,
> Not diagonalizing because representation xx is not done
>
Btw, I want to reduce I/O overhead by discarding `wf_collect` option, but
the following way doesn't work (the number of processors and pools for scf
calculation is the same to that in phonon calculation)
mpirun -np NUMBER_OF_NODESx24 pw.x
>
ph.x complains,
> Error in routine phq_readin (1):pw.x run with a different number of
> processors.
> Use wf_collect=.true.
>
The beginning output of pw.x,
> Parallel version (MPI), running on 96 processors
> R & G space division: proc/nbgrp/npool/nimage = 96
> Waiting for input...
> Reading input from standard input
>
and the beginning output of ph.x,
> Parallel version (MPI), running on 96 processors
> path-images division: nimage = 4
> R & G space division: proc/nbgrp/npool/nimage = 24
>
Do I miss something? I know it's inefficient to let pw.x use so many
processors, but it seems to be one requirement to let ph.x and pw.x have
the same number of processors.
Thank you!
--
*Best regards,*
*Coiby*
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