Parallel Instances of LabVIEW VI Generate Same Data

Updated Aug 8, 2018

Reported In

Hardware

  • USRP Software Defined Radio Device

Software

  • LabVIEW

Issue Details

I have made a reentrant VI to acquire data from a hardware resource and am trying to run two instances of the same in parallel. Despite using two different hardware resources to acquire data, I am seeing the same data in output in both instances of the VI.

Solution

This problem is commonly seen if you are using Queues in your application. If you wire the name input on an obtain queue function, the function searches for an existing queue with the same name and returns a new reference to the same.

To work around this issue, look for named queues in your VIs and ensure that every instance has a different named queue or the queues have been declared with no name.
 

Additional Information

You cannot use queues or named queues to communicate across application instances. If you attempt to communicate with a named queue in another application instance, LabVIEW does not return an error but you might not receive the expected results. More information on the same can be found in LabVIEW Help for obtain queue function.

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