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Subject: Re: V4 design issue: Should primitive data types have well defined precisions?
From: Ralph Lange <Ralph.Lange@bessy.de>
To: "Dalesio, Leo `Bob`" <dalesio@slac.stanford.edu>
Cc: EPICS Core Talk <core-talk@aps.anl.gov>
Date: Wed, 22 Jun 2005 15:13:31 +0200
Dalesio, Leo `Bob` wrote:

From a functional point of view - the DA approach gives you total flexibility.
What does it do to the complexity of the implementation and the performance? Does it have an impact on the server? Or just the client side?
I'm amused to see that we start discussing basic requirements and properties of an introspective data interface again. I thought this discussion was held and ended five years ago. Well....

You won't get higher flexibility and introspection without making the implementation and interface more complex. In a similar fashion, accessing predefined fixed data types will of course always be faster than using an introspective way to access data. So - yes, the implementation and the interface will be more complex.

For V3 all conversions were done in the CA server. V4 will move (almost) all conversion work into the client, making the memory and cpu footprint on the IOC generally smaller - this could partly be compensated by the use of C++, probably more for the memory than for the cpu load.

For performance measurements using an older version of DataAccess see the papers that Jeff and I were presenting at the ICALEPCS 2001 (http://arxiv.org/abs/cs.ni/0111026 and http://arxiv.org/abs/cs.se/0111036)

Ralph


Replies:
Re: V4 design issue: Should primitive data types have well defined precisions? Marty Kraimer
References:
RE: V4 design issue: Should primitive data types have well defined precisions? Dalesio, Leo `Bob`

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