Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Tue, 3 Feb 2009 11:07:22 +0100

On Monday 02 February 2009 23:18, Maren Purves wrote:
> Benjamin Franksen wrote:
> > On Montag, 2. Februar 2009, Till Straumann wrote:
> >> Benjamin Franksen wrote:
> >>> Our idea for an efficient implementation is based on the observation
> >>> that in a typical EPICS database there are only very few fields per
> >>> record that actually receive dbPuts (or get updated directly from
> >>> within base). Only for these fields is it necessary to provide
> >>> storage for the time of the last update. This storage will be
> >>> allocated on demand; each record must maintain a (typically very
> >>> short) list of (field index, timestamp) pairs; let us call it the
> >>> 'field update list' or short 'update list'. When reading the
> >>> timestamp for a field, first search the update list and use the
> >>> contained stamp if one is found, otherwise use the TIME field of the
> >>> record.
> >>
> >> How does that implement (b) ? If a field is never updated,
> >> shouldn't that field then report the time when iocInit() was
> >> executed?
> >
> > Ah, a good objection. It looks as if we need to distinguish between
> > fields that have
> >
> >  i)   never been changed (timestamp = iocInit time)
>
> only if PINI=Yes?

Surely not. Every field gets initialized at startup. PINI should be treated 
like all other processing.

> >  ii)  last been updated by record support (timestamp = record's TIME
> > field) iii) last been updated via dbPut or from base (timestamp = see
> > update list)

Ben
-- 
"TDD replaces a type checker in Ruby in the same way that a
strong drink replaces sorrows."       (byorgey on #haskell)

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System