Help on efficient SubVI interaction

Question

I really could use some advice with how my main program passes data to my SubVi, and how the SubVi handles it.  Right now my main program passes values into the SubVi as fast as it gets it.  The whole point of the SubVI is to perform an integral on my data.  However, the change in time (dt) is never constant, so I need to always be calculating dt as I go.  So I take current time T2 and subtract from it time T1, which has been passed back through the shift registers. 
My questions are these:
1. Is a while loop in the SubVi the best way to go?  In the main loop, the program runs continuously until I hit the stop button.  So I want the SubVi to run until the main loop finishes.  How do I stop the Subvi?
2.  Suppose the 4 fuel flow channels don't come in at the same exact time?  Let's say Fuel Flow 2 gets fed to the SubVi .002 seconds after Fuel Flow 1, and Fuel Flow 3 comes in slighty after 2?  How is the SubVi going to run?  Will it wait until all four channels of data are received before executing?
3.  If there is no timing control for the while loops, like a wait function, I understand the the while loop will execute as fast as it can.  Since I have a while loop in the main program feeding data, and a while loop in the SubVi, am I going to need to syncronize these at all?
I included the SubVi itself, and a picture of the main loop, since it has a lot of functions that are custom. 
I appreciate any help.. starting to get into more advanced programming! 
Thanks,
Alex

Answer 1

Thanks for responding so quickly!  I thought about what both of you said, and I've been trying to think of the best (and easiest) ways to implement your ideas.  In response to some of your thoughts:
Brad -
I wired the stop button in the main program to the SubVi.  I think this is what you meant.  Seems simple enough.  Not sure why I never thought of that before.  As far as the for loop, it would take me some time to think about how to do that.  If this idea with the while loop doesn't work out, I'll have to try that next. 
Lynn -
When I said I stop the program, I meant stopping it using a button control on the front panel, rather than abort stop button in the front panel taskbar.  I saw what you meant about having my controls outside the while loop.  It's obvious now.  So I put them inside the while loop.  Now they should be updating constantly.  As far as the other things you were mentioning, like putting indicators and TDMS write functions in seperate loops, I don't know too much about how to do that, but I'd like to learn more about it.  Do you have any good resources in the help or online that have some simple examples demonstrating this?  I would very much like to make this program run more efficiently.  I don't mind doing a reconfiguration of the program.
Ok, so here are the changes I made.  Pretty simple ones.  I attached the pictures of the SubVi and the Main.  All I did in the main was to route the true/false control to the SubVi.  Now the SubVi will run until i stop the main program.  In the SubVi, I placed the time and data controls in the while loop, so its constantly bringing values in from the main program and processing them.  However, the very time the SubVi run, you have this condition where the first time T1 is subtracting a value T0 that is produced by the shift register from the left side.  Since the loop hasn't run yet, I dont know what it's subtracting.  I'd like to have T0=T1, so I set up a local variable to initialize the shift register.  After that, I expect the shift registers to pass values back, so cases will run such as T2-T1, T3-T2 and so on.
This seems like the simplest way to get this to work.  Do you see any problems I don't?  Unfortunately, I can't "test" this, it needs to work the first time.. so I appreciate the help. 
And at the risk of sounding like a complete nerd, I love programming in Labview.  Lots of awesome challenges figure out and new ways to do things!
Thanks,
Alex
Attachments:
Main_edit.JPG ‏167 KB
SubVi_edit.JPG ‏95 KB