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Subject: How to write a python-based backpup tool?
From: emmanuel_mayssat@lynceantech.com
To: EPICS tech-talk <tech-talk@aps.anl.gov>
Date: Fri, 16 Sep 2011 09:58:57 -0700
Hello all,

I was looking at the existing backup utilities (burt,casr,sddscasr, etc).

To all those utilities you supply a request file (list of Pvs to save)
Now what do those utilities do?
Do they do a SEQUENTIAL 'caget' equivalent of all the Pvs?
or do they do some kind of 'smarter' operation, like get all the PVs at once?

Now I am interested in storing the PVs in hdf5 or sqlite files.
(assume 1 backup per file)
I could of course modify any of the existing backup tools.
Most of them are written in C, so the code execution is pretty fast.
(Is any one of them fast than the other? If so why?)


Now i am contemplating writing the code in python.
How would this python code cope with 50K+ Pvs?
(In other words, is there a limitation in pyepics? or a performance issue?)

<open container file>
for pvName in pvNames :
    pv = epics.PV(pvName)
    val = pv.get()
    <put in result in container file>
<write container file to disk>

I may be interested in using Cython, C compilation of python code of the above.
Not sure of the performance gain, but is any one of you using Cython?

-- 
Emmanuel

Replies:
Re: How to write a python-based backpup tool? Matt Newville

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