Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Tue, 14 Jul 2009 14:10:24 +0200

Have you ever needed to collect values such as a status bit from over a 
dozen similar devices, summarizing e.g. by calculating the maximum or 
minimum, or logical conjunction or disjunction? Did it ever occur to you 
that doing this via cascading calc record is somewhat less than elegant? If 
any of this sounds familiar to you, then check out http://www-
csr.bessy.de/control/SoftDist/nofun/ where you'll find support for a number 
of new record types that were inspired by features commonly found in 
functional programming languages, such as map, fold, etc. This is from the 
docs on the website (which are scant, sorry; this will improve):

collectRecord
  Collect data via input links and store values in an array field.

foldRecord
  Reduce an array to a scalar by folding an operation over the array, given
  a seed value for the accumulator. The operation gets the current array
  index, the current array element, and the current accumulator as input,
  and produces a new accumulator value as the result.

mapRecord
  Map an operation over an array, producing a new array. The operation gets
  the current array index and the current array element as input, and
  produces a new array element value as the result.

sfanoutRecord
  Distribute a single scalar value to multiple PVS, like a dfanout record,
  but with more output links and able to handle string values.

The operation in a fold or map record may be performed either as a CALC 
expression, as a subroutine, or via input and output links by another 
record. Elements are iterated starting from index 0 up to the maximum index.

An important feature is that the number of array elements resp. input links 
can be specified at compile time. This is done by setting the make variable 
NUM_LINKS (with a maximum of 1000 due to EPICS field name length 
limitation).

Have fun!

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System