Performance penalty with property nodes?

Question

In a specific application I have a front panel with three combo boxes and another three string indicators. Based on the selections made in the combo boxes, various messages will have to be displayed in the string displays. This naturally calls for multiple instances in the same VI where the combo boxes will have to be read and string display updates.
One choice would have been local variables ( of combo boxes & string indicators ) for passing the values around. But since this is going to make several copies and hit performance, I decided to use property nodes. And it works fine.
The question is, whether excessive use of property nodes has any adverse effect on performance ?
Thanks
Raghunathan
Raghunathan
LV2012 to Automate Hydraulic Test rigs.

Answer 1

Thanks! I would suggest to just do the experiment.
The attached little demo (LabVIEW 7.1) does the same thing (increment a I32 variable in a loop) in three different ways:
-- shift register
-- local variable
-- value properties
On my slow laptop, 10000 iterations take the following total time in ms.
shift registers: 3ms
Local variables: 5ms
Value Properties: 1891ms (!!)
Notice that the shift register solution would be much faster (more than 10x (or 1000000 in 20ms)) if the indicator is placed outside the loop, the only thing slowing it down is the update of the indicator.
In conclusion value properties are much more expensive than local variables or shift registers. If you just write once e.g. at the beginning of the program, it does not really matter, but once you do things repetitively in a loop, the costs add up. I always prefer wires because they also make the diagram easy to follow. Local variables break the dataflow and can cause race conditions. They have their limited use, especially in user interface related code. They have no business in pure computations.
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Attachments:
timers.vi ‏47 KB