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<== Date ==> <== Thread ==>

Subject: Re: Maximum (Minimum) Value of a Set of Readback PVs
From: Ned Arnold <nda@aps.anl.gov>
To: Tim Mooney <mooney@aps.anl.gov>
Cc: John K Munro Jr <jkm@ornl.gov>, Ernest Williams <ernesto@ornl.gov>, APS tech-talk <tech-talk@aps.anl.gov>
Date: Mon, 23 Jun 2003 13:01:10 -0500

The "select" record in base can select the highest value of 12 inputs. Configuring a select record in which each input is another select record would give you the highest value of 144 PVs ...



Ned




Tim Mooney wrote:
re...,

John K Munro Jr wrote:

Hi Ernest,

Is there a way (that someone has already implemented) with EPICS to
monitor a set of a large number (many dozens) of PVs used for readback
for the maximum (minimum) value in the set and to report the result?  I
would like to be able to display such a maximum (minimum) as part of
giving information about the status of equipment to the operator.


The most straight-forward solution might be to use a bunch of calcOut records.
Twelve of them would, in principle, handle 11 dozen PV's. However, with the
calc software currently in base, you can only compute the max of five (or
maybe six) PV's per calc record, because the calc string is limited in size,
and because you have to say something like "max(max(a,b),max(c,d))...


With newer calc software (currently in beta test) --

www.aps.anl.gov/xfd/SoftDist/swBCDA/postfix_R3.13.5.tar.gz

-- you can say "max(a,b,c,d,e,f,g,h,i,j,k,l)", and get 12 PV's per record.

Another straight-forward solution is SNL code, which would execute
more quickly, but be less convenient to modify or generalize.




References:
Maximum (Minimum) Value of a Set of Readback PVs John K Munro Jr
Re: Maximum (Minimum) Value of a Set of Readback PVs Tim Mooney

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