LabVIEW Idea Exchange

Cluster Size as a Wired Input:

• Easier to see
• More implicit
• Nearly impossible to forget to set it (if it were a required input).

It would be useful to have a node that could be fed any wire and return the size (in bytes) of the data on that wire. In other words, the node would return the number of bytes that the wire occupies in memory.

For example, the node would return a value of:

• 1 byte when fed a U8 wire
• 2 bytes when fed a U16
• 4 bytes when fed a I32
• 8 bytes when fed a DBL
• 800 bytes when fed a 1D array that contains 100 DBL elements
• 9 bytes when fed a cluster that contains a DBL and a U8
• 9 bytes when fed an object that contains a DBL and a U8
• 18 bytes when fed an object that contains two other objects that occupy 9 bytes each
• and so on

Notes

• The node would would enhance LabVIEW programmers' ability to monitor and audit memory usage.
• The node may serve as an additional tool to detect memory leaks (by repeatedly calling the VI on the same wire and checking whether the size is going up).
• The node would simply be interesting to programmers interested in performance and would enable programmers to learn more about LabVIEW internals.
• The node would be useful especially to query the size of complex data structures, such as objects that contains other objects that themselves contain objects, or clusters that contain arrays, or arrays that contain clusters, or objects that contain DVRs.
• I would be happy if the node had a second input named "Mode" (or similar). This input may be a typedef enum with items named "Shallow Measurement" and "Deep Measurement" (or similar). This input could be required, recommended, or optional.
  • When "Shallow Measurement" mode is selected, the node would return the size of all the by-value data fields in the main input wire, but would not add up the size of data referenced by DVRs or other references. For example, a wire that contains a cluster that contains a DBL, a U8, and a DVR would return perhaps 13 bytes (8 + 1 + presumably 4 bytes for the DVR reference itself). It would not add to the result the size of the data referenced by the DVR.
  • When "Deep Measurement" is selected, the node would recursively scan all data structures, including DVRs and other references.
• In both "Shallow Measurement" and "Deep Measurement" modes there should be no limit to the scanning depth. In other words, if a cluster contains a cluster that contains a cluster and so on, they should all be measured regardless of the nesting depth. Similarly, if "Deep Measurement" is selected, and a DVR contains a DVR that contains a DVR and so on, the data behind all these DVRs should be added to the total.
• When in "Deep Measurement" mode and fed a Queue reference wire, the node could perhaps return the size of all the data in the queue. In other words, the size of all the elements present in the queue.
• Perhaps the LabVIEW compiler already uses a "Get Data Size" function internally? If such a function already exists, perhaps it would be relatively straight forward to expose it as a node in the palettes?
• Perhaps the best location for this node would be in the Programming >> Application Control >> Memory Control palette.

Thanks!

This idea came from customer Jason Willis during an NIWeek 2012 brainstorm session with LV developers. To me, it seemed like a good idea, so I figured I would post it to the community to flesh it out and see what kudos it gets.

When you have a reentrant VI, you have the one real VI and many clone VIs. Debugging the clones is hard. One way to make it easier might be to make the probes behave like the breakpoints do.

When you put a breakpoint on an individual clone, only that clone gets the breakpoint. But if you put a breakpoint on the real VI, all the clones get that breakpoint. That gives you a way to stop at a point of execution regardless of which clone gets pulled from the clone pool.

We could make probes do the same: if you put a probe on a real VI, any time the block diagram of a clone gets opened, a probe would be added to its wires in the same locations as on the real VI. If you removed the probe from the real VI, all the duplicate probes on the clones would go away too. But if you added a probe to a clone, the other clones would not get a probe.

Searched briefly but couldn't find any ideas about this.

I know we have the ability #via_ignore comments to ignore specific tests for a specific VI, but I am looking at a different use case.

Here's the use case, I use DQMH. When you create a new DQMH module there is a lot of plumbing code that comes with it. It's standard stuff. Very rarely do I have to open or edit it. Much of it is scripting generated. It often fails tests but I don't care. In addition to failing, it takes up test time, which slows my feedback loop. I would a way to signal to VI analyzer to skip these files. I know I can use the VIAN API to limit the files it checks, but I was thinking there had to be a better way. 

Implementation Ideas - I had 2 main ideas

- Regex matching on VI names - with the regex pulled out of a text file somewhere ala gitignore. Many of the DQMH generated VIs have standard names, so that is easy. When generating events, they don't but you could easily add a prefix/suffix or something that the regex would pick up.

- Using the Tag API to tag the VI. I like this because the scripting can just apply the tag or apply it to the template the scripter uses. Downside is: kind of hidden from the user and perhaps if I decide to make some edits to this VI  I may want VIAN to stop ignoring it and it's not immediately obvious how to do that.

Note:

I picked the Execution and Performance Label because it didn't seem to fit any of the labels easily. If this is the wrong label and you are an admin, please relabel it.

When programming with large applications, often times you'll have clusters carrying a lot of information.  If you hover over the cluster wire and observe Context Help, you might see something like this:

This Context Help window above is rather large and doesn't necessarily make it any easier to see the structure or contents of the cluster. My proposed idea calls for the ability to expand or collapse the cluster contents within the Context Help window, such as this:

What do you think?

I propose that Case Selectors should accept any type of reference, and the two cases generated are "Valid Ref" and "Invalid Ref". (This would be very similar to the current behavior of the Case Selector accepting errors with the two cases of "Error" and "No Error".)

The current behavior using "Not a Number/Path/Refnum" is very unintuitive. It requires the programmer to use Not Logic (i.e., do something if the reference is "not not valid").

On a For Loop that is configured to have parallel iterations there is a nifty feature when using errors on a shift register.  This feature is explained in an article here.  It basically ensures that For Loops that run 0 times, will preserve the incoming error as if the tunnel was a shift register.  However this feature also means that errors from iteration 0, won't be passed into iteration 1.  What is returned if the loop runs 0 times is just the incoming error.  But if it runs for more than that, the errors are all merged and returned will be the first error seen.

This idea is just to allow this already existing feature to work on non-parallel configured For Loops.  When would this be useful?  Say I want to delete an array of files.  I want to attempt to delete all files, even if there is an error in trying to delete some, just keep trying to delete the other files.  Initially you may think this:

But that has the clear problem that if the incoming array is empty, then the error will be cleared.  So we often do something like this.

And honestly this bit of code isn't that big of a deal, but this feature already exists.  However it only works on For Loops that are configured to run iterations in parallel.  In this case I might be attempting to delete files in a specific order due to their placement on disk, and running in parallel isn't what I want.

Since not everyone wants all errors in loops to act this way it would need to be a right click menu to turn the tunnel into a normal one, a shift registered one, or a preserve and merge one.

That is what I want.