[Pw_forum] Fortran runtime error

[Lorenzo Paulatto]

On Sun, September 13, 2009 14:04, Ihsan Erikat wrote:
>  when I put job for 2x2 surface the cluster work very well but when I put
>  the job for 4x2 surface it give me this error
>  Fortran runtime error: ALLOCATE: Out of memory. on the shell

Dear Ihsan,
the error message is quite clear: your hardware does not have enough
memory for the calculation you are trying to do!

There are a few measures you can take to reduce the memory usage:
1. if you are using pools, reduce the number of pools, it requires more
communication between nodes, but reduces the memory usage.
2. if you are using norm-conserving pseudopotentials try ultrasoft or PAW
instead; more in general try to do more accurate test on convergence with
respect to wfc and rho cutoff
3. if you have a slab geometry you may still have good results reducing
the amount of vacuum (you'll have to test the convergence wrt the amount
of vacuum)
4. if you are using a computation cluster, run the code on more processors
5. if you are using a PC, buy more RAM
6. us cg instead of david diagonalization, but only as a last measure

best regards

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/



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