Properly close multi loop application

[hellolv]

Can someone show me an example on how to properly close an multi-WHILE LOOP application?

[altenbach]

There are many possibilities. (local variables on one singe stop button for example). I prefer event structures.

see e.g.: http://forums.ni.com/ni/board/message?board.id=170&message.id=136388#M136388

[Anthony_de_Vries]

Don't want to hijack the thread....   but isn't it bad style to have multiple event structures like that?   Or is that only a problem for dynamically registered event?  

I'm thinking about this thread: http://forums.ni.com/ni/board/message?board.id=170&message.id=237840&view=by_date_ascending&page=4

Personally, I generally use local variable/property nodes, or have a (command) queue in the loop, with either a special stop command for the loop,  or the loop simply terminates when the queue is unavailable.   (Like the producer/consumer design patterns that you can select when creating a new vi.)

Message Edited by Anthony de Vries on 10-18-2007 05:27 PM

[altenbach]

I don't really use dynamic events, so I cannot comment on that specific thread, but for plain events I never had any issues with multiple event structures tied to the same FP event.

In my opinion, the following are OK:

• Multiple event structures serving the same FP event (e.g. "stop:value changed" in this case). Each in it's own while loop.

Not OK are the following (again in my opinion):

• Multiple events in the same loop (unless all are "transparent" with 0ms timeout). Still, this is not something I would do.
• event structures within event structures
• event structures inside case structures
• event structures inside certain sequences (if any of the frames contains delays).
• events containing long delays.
• events NOT in a while loop (except for dialog style VIs that don't have any while loops)
• events containing interactive while loops (short "math" while loops are of course ok, e.g. as used in a newton iteration)
• ...

In summary: any event topology that prevents the event from being serviced by the code dataflow within a short time is NOT OK.

This is my own list. Have a look at the NI documentation for other more details. I cannot find any objection against firing multiple event structures in parallel. 🙂

[altenbach]

---

@Anthony de Vries wrote:
Personally, I generally use local variable/property nodes, ...

---

My solution has the advantage that the loop rate can be extremely long and the stop still occurs immediately. Imagine you have a logging loop that takes a snapshot every hour, using the event timeout. Pressing the stop breaks the timeout and finishes the loop immediately and you can even trigger a final snapshot if desired.

Sure you can use other methods to do the same, but it will probably be more complicated.

[Anthony_de_Vries]

I absolutely agree, your solution of using multiple event structures is very neat.   I think I will start to use them as well, for exactly the reasons you mention.    Just wanted to make sure I'm not going to run into troubles...