[molpro-user] File I/O on molpro2008 parallel version

[Manhui Wang]

Hi Neeraj,
     There are at least two kinds of files in the scratch, one is EAF
(Exclusive Access Files)  which can be only accessed by a single
process, and another is SF (Shared Files) to which multiple processes
can read and write independently.  For a particular job, each process
needs a certain amount of space for EAF files. This means the total
space will increase linearly if many processes are used, but for each
process the used space is roughly the same.
    For many applications, EAF files may be very large. Molpro output
also summarizes the total used space. Here is an example, where DISK
USED indicates the total space used for EAF and related, and SF USED
indicates the total space used for SF
(1) job run with 2 processes on 1 node
 DISK USED  *         9.96 MB
 SF USED    *         3.05 MB
 GA USED    *         0.29 MB       (max)       0.27 MB       (current)

(2) job run with 4 processes on 1 node
 DISK USED  *        19.68 MB
 SF USED    *         3.05 MB
 GA USED    *         0.29 MB       (max)       0.27 MB       (current)

In addition, molpro2009.1 should clean up the scratch files after every
normal termination. For your case, it depends on what type( EAF, SF?)
the large files belong to, and how you run molpro on multiple nodes (how
many processes each nodes?).

Best wishes,
Manhui



Neeraj Rai wrote:
> Hello all,
> 
>      So far I have run molpro calculation on a single node with many
> cores and lot of memory and it wrote nearly 200Gb of in the temporary
> files on the scratch space on that particular node. If I were to run the
> same job with multiple nodes each with much less memory (distributed
> memory paradigm) will each node write these large files on the scratch
> space or read/write is done on one node and then distributed across node
> so my disk requirements will not balloon with more nodes I request. or
> if codes writes on individual nodes will the file size be smaller?
>   
>      Thanks.
> 
> -- 
> Regards,
> Neeraj.
> 
> 
> 
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-- 
-----------
Manhui  Wang
School of Chemistry, Cardiff University,
Main Building, Park Place,
Cardiff CF10 3AT, UK
Telephone: +44 (0)29208 76637