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instances revealed when doing a compare

Hi All,


I've been comparing two VI hierarchies and have come across an unusual set of returns;


The VI, "Measure", returns a number of instances that are different. 






In each case it appears to be the express VI, 'Display Message to User', that is causing the difference/ instance.


Does anyone know why the express VI's are causing these instances.  They don't appear to be re-entrant, I'm a bit baffled.




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Hi Sean,


Thanks for posted about this issue. Firstly I wanted to reassure you that, dispite what the compare list implies, there are not multiple instances of your top-level VI. However, I agree that the naming convention being used is missleading.


To replicate your issue I made a simple vi which called 3 express VIs in sequence. I saved this VI (, and made a copy of it ( Effectively, I now had 2 identical VIs with slight different names. While both VIs were open in memory, I went to tools >> compare. As you can see below the compare Window shows a main instance of the top-level VIs PLUS x3 instances of the top-level VI (one per Express VI).




I them compared the 2 top-level VIs (ie. and As you can see below, the comparision tool (correctly) found 0 differences.


Top Level Compare.JPG


I then compared a top-level VI (ie. with an instance of that top-level VI (ie. As you will see, the tool found many differences. This is because we are NOT actually comparing 2 instances of but we are actually comparing with one of the ExpressVIs.


Top Level and Instance Compare.JPG


I wanted to take this oppertunity to reassure you that, dispite the implication, the additional of each ExpressVI does not spawn multiple instances of the top-level VI, and that everything is behaving as intended. However, I do agree that the current naming convention for each Express VI is rather confusing. I will raise this as a corrective action request with the LabVIEW R&D team to see if we can make this a little more obvious in a future release.


Thanks for bringing this to naming convention oddity to our attention. But, to assure you one last time, from a programmatic/functional perspective, everything is working as expected.


Hope this has been helpful,

Kind regards,

Rich Roberts
Senior Marketing Engineer, National Instruments
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