Communication between threaded VIs with queues

[BullBalls]

Hi,

I would like to communicate between VIs (thread structure) with queues. But sending messages with queues increases the memory until crash.

I try to release the queue each time I send new message, but I also destroys the recipient !

Any suggestions for reliable communication between VIs (launched dynamically) -> Like Windows messaging ?

Thanks in advance for your answers.

[Eugen_Graf]

You have not to destroy/release queue after each sending.

Open your queue and connect the reference on both loops. So the one loop enqueues the queue and the other one should dequeue them. After you exit both loops you can release the queue.

I use queues very very often (up to 20 queues), but I can't confirm that the memory usage increases.

Eugen

[BullBalls]

Hi Eugen,

Thanks for your answer.

You write "Open your queue and connect the reference on both loops". This will work fine if both threads are in the same VI, but I can't do so because they are both in separate VIs, called dynamically... Thats my main huge problem.

Any other suggestions about how communicate between VIs called dynamicaly ? What kind of structure should I use ?

Thanks

[tst]

Queues work fine for communicating between different VIs - when you obtain a queue, you have the option of entering a name, which obtains the same queue.

There are two ways in which you can run out of memory:

1. You enqueue much faster than you dequeue. The queue grows unbounded until there is no more memory. There are several solutions for this. You can define a maximum size for the queue or occasionally flush the queue, but the best solution is usually not to enqueue data unnecessarily.
2. You obtain the queues in a loop. This produces a new reference each time which consumes memory. The solution is to obtain the queue once.

The real solution depends on what it is you are actually trying to do, but I'm suspecting you might want a notifier - unlike queues, a notifier only maintains the most recent value and so will not grow unbounded.

I suggest you post more details about what it is you want to do exactly. Posting images of your code might also help.

[TCPlomp]

If you want to connecgt to an existing queue, you should use a name for your queue. Be sure the datatype is the same on every instance.
Besides that if you close the VI that opened the first instance of the queue goes Idle the queue will die (as far as I know)

Ton

[Eugen_Graf]

Here you have an example.

[Eugen_Graf]

And here the screenshot of the Main.vi, which starts both loop-VIs.

.

Message Edited by Eugen Graf on 02-06-2008 03:54 AM

[Eugen_Graf]

Ok, if you start your VIs dynamically, than you can use the VI server method "Set control Value" to let the VI know the Queue reference.

OR you can open the queue reference in both VIs before the loop. The unique NAME of the queue should be the same in both VIs, than you have the same reference of your queue.

[BullBalls]

Hi everybody,

Thanks for all of this answer. I will try those solutions and check for the memory size usage...

Thanks again.