Initialisation of Feedback Nodes #2

[SercoSteveB]

The following VI was created, saved and then executed twice.  What is the value of Numeric Value Out following the second execution of the VI?

a) 8

b) 16

c) 32

d) 64

[crossrulz]

D

[whitecr]

And: A

What ever the time user may run this vi. During first iteration of for loop the 0 and 1 are initialized in the feedback node. So at the end of the execution we will get 8.

Ans: D

Crossrulz is correct:

In the above VI intilize on compile or load is selected so if it run twice we will get the ans as 64.

Nice question stev for all these days i am using feedback node I didnt notice this option.

Today I learned a new thing.

Thanks steve.

[whitecr]

Hi Steve previous question and this looks like same

[sathishp91]

D

[LordNobady]

D

@whitecr

It is differend. watch the top feedback node.

[hemanth.wnp@gmail.com]

A

Hi Steve Previous question and this one is same.

[SercoSteveB]

I was a bit mean doing two questions that appear to be identical on consecutive days.....but that's how I roll. 

Check out tomorrow for more on the same theme.

[MrStevenUND]

Top feedback node initializes when VI loads or compiles.  Bottom one initializes on first call of the VI (ie, every time the user presses the run arrow)

Ans: D.

I predict tomorrow's will have the rhombus, which initializes on first call of the vi...  

http://zone.ni.com/reference/en-XX/help/371361J-01/lvconcepts/block_diagram_feedback/

[SercoSteveB]

Close.....but no cigar.

[ashwinilele]

D

[rsmrostov]

I would say A, the majority claims D however, can someone please explain why?  both feedback nodes are initialized one by the loop counter (so every time it's ran the init value is 0) one is moved to the outside of the loop initialization which will also initialize every time the loop is ran (just like a shif register).

sorry, looked under the previous question, but posted here.

[rsmrostov]

D

[mini09]

That was a nice point to be noted in this post. Agreed with D.

[SercoSteveB]

Answer: D.  Nice one crossrulz, whitecr, sathishp91, LordNobady, MrStevenUND, ashwinilele, rsmrostov & gnshmrthy.

A bit sneaky this one, but it always pays to read the question.

[echacon95]

Not familiar with the concept of feedback node. Would someone mind explaining the block diagram and how the value of 64 results?

[crossrulz]

Feedback Nodes behave exactly the same as shift registers: they return the value from the previous iteration.  The difference here is when the shift register is initialized: on first call vs. globally initialized (on load).

[M.P.Bharghavi]

Ans:D

64

[Simha@999]

In labVIEW 2020sp1 , I have ran the VI twice but even though answer is 8

[crossrulz]

Naidu@00, your problem is how the top Feedback Node is initialized.  Right-click on it and choose Globally Initialize->Initialize On Compile Or Load.  What this does is cause the top FBN to keep the value from the last run while the bottom FBN will re-initialize between runs.

[Simha@999]

Oh, I see Thanks Crossrulz