[Pw_forum] -D__NEW_PUNCH option

[Konstantin Kudin]

> Of course, the local scratch
> disks are preferable. But after that when the code will finish, the
> files in the scratch directory will be deleted, and this is not
> preferable for me because I may have to use these files for restart.


 Dear Sergey

 I looked into the logistics of such a thing some time ago. We have a
cluster where each node has a scratch space uniformly named as, say,
/tmp. These directories were also accessible from any node by a longer
name.

 Basically, the wavefunction files split across nodes (*.wfc) in each
/tmp are not worth bothering with, so just discard them. They are easy
to regenerate if *.rho and *.pot are available. Other useful files only
exist on the main node for a given run.

 Immediately before the job is run a wrapper script copies files with a
given prefix from a central location to the main node /tmp so that the
restart information can be read. After the job is finished, the same
wrapper script copies back files with a given prefix from the main node
/tmp to the central location. All the *.wfc files are discarded at this
stage. I could provide my setup for such manipulations.

 Alternatively, perhaps, one could modify PWSCF to have 2 locations for
temporary files. That should be an easy hack. One location would have
everything but the *.wfc files, the other location would be just for
*.wfc files. Then these *.wfc files could go to the local scratch
space, and discarded whenever. The rest of the files could even go to a
central location. I think that using NFS for files other than *.wfc
would be reasonably mild for the network load. You could try this and
see if you admins are still unhappy.

 Kostya

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