| Simultaneous write on textfile over NFS [message #69722] |
Wed, 10 February 2010 01:29  |
Johannes Korn
Messages: 5
Registered: January 2010
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Junior Member |
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Hi,
I often run idl programs which utilize only one CPU core (for loops).
The output is a text line appended to a file.
To exploit a multicore I run multiple instances with different parameter
setups. The output goes to different files. After all jobs are completed
I manually merge the files.
This ways I have to keep track which file contains what output and so on.
My question, what happens if I use the same output file for all jobs. Is
it save?
This means every job would write about every 15 seconds a line like that.
OPENW, u, 'file.txt', /GET_LUN, WIDTH=250, /APPEND
printf, a, b, c
FREE_LUN,u
What if two write accesses collide? Will the file be corrupted? Will
there be an error? Will the second job wait until the first one has
closed the file?
Filesystem is NFS.
Regards,
Johannes
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| Re: Simultaneous write on textfile over NFS [message #69817 is a reply to message #69722] |
Wed, 10 February 2010 07:04  |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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Johannes Korn schrieb:
> Hi,
>
> I often run idl programs which utilize only one CPU core (for loops).
> The output is a text line appended to a file.
>
> To exploit a multicore I run multiple instances with different parameter
> setups. The output goes to different files. After all jobs are completed
> I manually merge the files.
> This ways I have to keep track which file contains what output and so on.
>
> My question, what happens if I use the same output file for all jobs. Is
> it save?
>
No
you need one processor which serializes your output and which takes care
on the order.
May be read a bit about mpi / openmp
cheers
Reimar
> This means every job would write about every 15 seconds a line like that.
>
> OPENW, u, 'file.txt', /GET_LUN, WIDTH=250, /APPEND
> printf, a, b, c
> FREE_LUN,u
>
> What if two write accesses collide? Will the file be corrupted? Will
> there be an error? Will the second job wait until the first one has
> closed the file?
>
> Filesystem is NFS.
>
> Regards,
>
> Johannes
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