[Pw_forum] pools and neb

[carlo sbraccia]

Dear Antonio,

> pw 2.*  sometimes crashes when we use k points paralization with neb.

you should provide the input that makes the code to crash. I have been 
using neb with parallelization on k-points for a long time and I've 
never had troubles.

> My questions:
>
> 1) How to use image paralization? (some example of input file)

for image parallelization just use

mpirun -np N pw.x -nimage M -in input > output

Of course M < N and M < num_of_images. Much better if M is a whole 
divisor of num_of_images.

> 2) is 3.* affected by this bug?

Maybe, since the "bug" has never been spotted before.

> 3) Is it possible to convert 2.* path file to 3.* path files for a  
> restart?

I think so: just remove the section "QUICK-MIN FIELDS" in the path file 
and restart.

> 4) Is 4 processors for pool and as pools as k-points the best  
> performance achieving setup?

It is impossible to give a general answer: it depends on both the system 
size and on the computer you are using.

However, I already posted a similar message a couple of months ago 
(http://www.democritos.it/pipermail/pw_forum/2006-March/003803.html) .

carlo