How do custom probes affect the vis execution time

[Tom_Gloor]

If I set custom probes in an running application, the
vi seems to execute slower than without custom probes.
Does anybody know how much delay time a custom probe
causes?

[JRA]

I don't think there is any constant time it adds to a VI's execution. However, it does make sense that it would take longer. Custom probes are really just subVIs that run when execution reaches them. Once execution reaches them, the probe has to fully execute before your application moves to the next subVI. As a test, I created a custom probe which just had a wait function and waited for 5000 ms. It added 5 seconds to the overall execution time of my VI. So, any code you put in a custom probe, whether it be simple comparisons (neglible change in performance) or even full data acquisition (more change in execution time), a custom probe will add to the overall time of your application.

[tst]

By the way, standard LabVIEW probes also seem to slow execution down. I'm not sure if this is because of the graphic effort involved or if it's something to do with the execution itself. I created a small VI with a for loop running a million times and auto-indexing the i out as an array. With no probes or with probes outside the loop, this took about 150 ms. With probes inside the loop, this grew to about 700. If any of the experts (Rolf? Dennis?) know exactly what causes this I'd be happy to know.

[JRA]

That's a great observation. I expect it's for the same reason as custom probes. Basically, all probes are like subVIs that must execute, which will of course take time. Since they behave just like subVIs (won't execute until inputs are received and outputs will not be returned until it's finished executing), you are basically adding the execution time of that subVI to your overall execution each time you run it.