local variables vs property knots->value

[Sneff]

What is the advantage of local variables versus property knots (value)?

They tell in the manual, that for every local variable there is always a copy made of the original

input/indicator. If i use the property knots (value) no copy is made.

So what is the use of local variables?

Which methods exits else to avoid too long wires?

Sneff

[MikeS81]

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Sneff wrote:

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Which methods exits else to avoid too long wires?

...

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Hi Sneff,

"to long wires" doesn´t exists. To use wires is better then everything else! A good solution to have a clearly arranged block diagram is to use a state machine architecture.

Mike

Message Edited by MikeS81 on 05-06-2008 01:43 PM

[Norbert_B]

As Mike already told you, you should try to avoid variables (both locals and globals) just as usage of property nodes value. There are several reasons for this:
- Bad diagram design with variables
- Trying to work around a bad architecture by using variables instead of switching to a fitting one
- race conditions (insecure datamanagement)
- performanceissues

Besides that, using variables vs propety nodes (value) are the following:
- property nodes are always executed in the UI thread => slow
- variables as well as the property node copy the data of the control\indicator in case of reading => exposed, well, predestinated for race conditions

hope this helps,
Norbert

[Sneff]

Thank you,

but what do you mean with state machine architecture and race conditions?

Greetz

Sneff

[Norbert_B]

http://en.wikipedia.org/wiki/Race_condition

http://en.wikipedia.org/wiki/State_machine

If you want to know how a state machine in LabVIEW looks like, you should either try the example finder or the "design patterns" in the template browser (File->New).


hope this helps,
Norbert

EDIT: Updated links for "link-behaviour"


Message Edited by Norbert B on 05-06-2008 07:29 AM

[Mathan]

study here and here

[Sneff]

Yeah, thank you that helped.

I try to code my VI like a state machine.

This fits perfectly to the rest of my concept.

Greetz

Sneff