Experimental Physics and
Industrial Control System

Hi Mark,

On 2011-07-21 Vigder, Mark wrote:
> I started building an IOC using the histogram record and it gave me an
>  "unknown type" error. I checked the source (I'm using EPICS 3.14.12) and
>  even though the record is defined in <EPICSBASE>/src/rec it's not included
>  in <EPICSBASE>/src/misc/base.dbd. In fact it's the only record defined in
>  /src/rec that is not there.
>
> This leads me to a number of questions:
>
> -Is this just a bug? Or is histogram an obsolete record?

Interesting; I'm going to guess that you're not necessarily the first person
to *notice* this, but I think you're the first to point it out on tech-talk.

I don't believe the omission is deliberate, it's just that the histogram
record type is fairly specialized and is not used much any more.  It it looks
like the last time anyone made any significant changes to the code (other than
just updating it to match API and coding style changes elsewhere in Base) was
in October 1998.

> -Does this mean nobody is actually using the histogram record?

I can answer that for the APS: we have a total of 4 (four) histogram records
across the whole of our 320-odd IOCs and well over half a million records in
our accelerator control system.  Any other histogram users out there want to
speak up?

> -If nobody uses histogram, what do they use? Waveform?

I would guess other people are using subroutine or array subroutine records,
and for some uses just a calc or calcout record might suffice.

- Andrew
--
Optimization is the process of taking something that works and
replacing it with something that almost works, but costs less.
-- Roger Needham