Strange Local Variable Performance

Question

I have been working on improving the performance of my interface, and I came across some performance results that I don't understand. I have a local variable (local!initialData) that calls an expression rule. I have a second local variable (local!dataCapture) that is just a copy of local!initialData. Looking in the performance tab of the interface, both of these local variables take the exact same amount of time to evaluate (+/- 1ms). However, I would expect local!initialData to take longer than local!dataCapture since local!dataCapture is just copying the data from local!initialData, not running the expression rule. 
 Can anyone explain this to me? Is this to be expected, or am I doing something wrong to cause this to happen? 
 I have attached an image of the performance numbers for these two local variables and have included the definitions of both below. 
 Thanks in advance! 
 local!initialData: a!forEach(
 local!orderLineData,
 rule!SSTH_initialData(
 orderLineData: local!orderLineData,
 index: fv!index,
 desiredOutput: "dataCapture"
 )
),
local!dataCapture: local!initialData,

Stefan Helzle · Accepted Answer

I see a few other things I would do different, but there is nothing wrong with that code snippet. 
 It could be that the second local wants to evaluate, but has to wait for the first one to complete. This would explain the one millisecond difference. But this is more guesswork than deep knowledge.

Mike Schmitt · Answer

Jack Ferguson said: Out of curiosity, what do you see that you would do differently 
 Honestly, this might be a case where you need to take the "performance numbers" with a grain of salt. I think Stefan is probably right i.e. the downstream one is showing a similar number only because it's waiting on the prior dependent, i.e. the total time isn't even necessarily the combination of the two numbers, but rather perhaps the intersection, if you get my drift (i.e. it's displaying the same for both but they don't represent the total). It's hard to tell for sure of course.

Mike Schmitt · Answer

Is the data being loaded into local!dataCapture a bit bulky? That could explain why the copy is also taking some time. Beyond that, just remember that execution times can be a bit random between different runs of the rule.

Strange Local Variable Performance

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