While Loop - Iteration Terminal

Why the iteration terminal in my upper while loop counts only to 1? (err_while.vi)
Petr Bilovsky
Attachments:
err_while.rar ‏289 KB

Hi PetrB
I tested your vi. Results are unexpected.
Upper loop runs to 10 and stops.Down loop keeps running and it should not, because the inputs to AND gate are TRUE.
I deleted down loop and copied upper loop ant Now they stop at 10.
I don´t know your DLL, so try to make it reentrant to avoid side efects.
Hope this helps.
Alipio
"Qod natura non dat, Salmantica non praestat"

Similar Messages

What happens to the while loop iteration counter if it runs unchecked?

I want to use the iteration counter to initialise a value on the first loop of a while statement. ie i = 0, x = 100. Fine. The application I am building will be left to run for weeks or months on end without stopping (hopefully :¬)). What happens to the iteration counter in this situation? Does it reset to 0 or what? I don't want it reinitialising any values while the loop is running other than when it starts.
I set up a while loop to try to figure out what happens and the iteration counter stops at 2147483648 which is 2^31 - 1.
Any help would be appreciated,
Thanks,
Niel.

It might be something you already looked at, but perhaps it's an option to perform the initialization outside (before) the while loop. That way it will be initialized correctly only once, no matter what the iteration counter does.
Of course if you need the counter for other purposes than initialization you might have the same problem...
Note that a lot of the timer functions also overflow after a certain time (I believe 24 or 48 days?) so be careful running very long loops (but you already knew that probably).

While loop not terminating

hmm. very strange to me. i have a condition that if a person enters QUIT then the program should terminate but for some reason its not terminating.
import java.util.*;
class BicycleTest {
     public static void main(String[] args) {
          BNode start, tail, next;
          start = null;
          Scanner s = new Scanner(System.in);
          System.out.println("Enter name");
          String name = s.next();
          if(!name.equalsIgnoreCase("QUIT")) {
               start = new BNode(new Bicycle(name), null);
               tail = start;
               while(true) {
                    name = s.next();
                    if(name.equalsIgnoreCase("QUIT")) break;
                    next = new BNode(new Bicycle(name), null);
                    tail.setNext(next);
                    tail = next;
}

jverd when you say an older version that means the
java version or the compiler? No, an older version of your code. Like you changed it (to what you first posted) but forgot to save or recompile. Maybe before you had equals instead of equalsIgnoreCase, or something like that.

I have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

i have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

Hi fais,
Following through with what JB suggested. The steps involved in replacing the inner for loop with a while loop are outlined below.
You can replace the inner for loop with a while by doing the following.
1) Right-click of the for loop and select "Repalce" then navigate to the "while loop".
2) Make sure the tunnels you where indexing on with the for loop are still indexing.
3) Drop an "array size" node on your diagram. Wire the array that determines the number of iterations your for loop executes into this "array size".
4) Wire the output of the array size into the new while loop.
5) Set the condition terminal to "stop if true".
6)Drop an "OR" gate inside the while loop and wire its output to the while loops condition terminal.
7) C
reate a local of the boolean "stop" button, and wire it into one of the inputs of your OR gate. This will allow you to stop the inner loop.
8) Drop a "less than" node inside the inner while loop.
9) Wire your iteration count into the bottom input of the "less than".
10) Wire the count (see step 4 above) into the top input of the less than. This will stop the inner loop when ever the inner loop has processed the last element of your array.
Provided I have not mixed up my tops and bottoms this should accomplish the replacement.
I will let others explain how to takle this task using the "case solution".
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Stop dependant while loops with 1 button

Hi,
I am developing a utility that allows a user to configure up to 2 devices (both use same driver with a different board number), click initialize, which then brings up a file dialog and displays arrays for the data to be collected and some error messages for each measurement. The user then clicks the Start/Stop button to begin collecting and logging data. Currently i have a Wait(ms) block to allow the user to set often the measurement should be made. Currently the Start/Stop button allows collection to be started, paused, and started again. My problem is trying to have a master stop button that should stop all loops immediately when it is pressed.
I tried using a global variable for the stop button, but the measurement and logging while loop doesnt stop until after the wait(ms) block times out. Can anyone give suggestions. If i need to restructure the VI into different loops, I can do that. I just want to understand the right way to program something like this.
The VIs are attached. I removed the device specific measurement VI so that anyone can open the vis and run them to see how it works.
Attachments:
2Devices_withoutMeasurementVI.vi ‏112 KB
BuildOutput.vi ‏27 KB
stopGlobal.vi ‏5 KB

Ok. I had a chance to take a look at your code and I think you don't quite understand the concept of "dataflow". Let me see if I can help.
First of all...when I refer to your upper structure, I am referring to the first while loop, sequence structure, and subsequent while loops. When I refer to your lower structure, I am referring to the while loop containing the event structure. Just so we get our terminology straight.
I believe that you are under the illusion that your upper structure contains three parallel while loops. It does not. It contains three SERIAL while loops. There is dataflow dependency between the while loops. The sequence structure requires data that is not available until the first while loop has finished executing, so the sequence structure cannot start executing until the first while loop has terminated.
The second while loop requires inputs from the first frame of the sequence structure (which, by the way, you don't need and should get rid of...the sequence structure, I mean), so it cannot start executing until the first frame of the sequence structure has terminated. The third while loop requires inputs from the second while loop...so, again, the third while loop cannot run until the second while loop has finished executing.
Now, for your stop button. You have that global stopping all three loops. So here's what is happening in your program:
Your program starts. The first while loop executes in parallel with the loop which contains the event structure.
At some point you press the "stop" button. Both the first while loop and the loop containing the event structure finish executing.
The first frame of your sequence structure executes.
The second frame of your sequence structure executes. The second while loop reads the "stop" value from the global, so it executes once and then finishes.
The third while loop starts executing. Again, the loop reads the "stop" value from the global, so it executes once and then finishes.
Then your program terminates.
You need to restructure your program, because right now it doesn't make any sense at all. Your block diagram would benefit from some serious tidying up as well, your wiring is a mess. I suggest you look into a state machine architecture for this program.

Dsc periodic I/O "stop while loop" usage?

I'm using LabView 8.5.1 with DSC. I have created a working periodic I/O server VI and successfully deployed it.
The one glitch I am running into is what happens when the Shared Variable Engine I/O process is terminated. I normally terminate it by using "remove process" from Variable Manager.
The I/O server wizard lets me choose the while loop for termination during the build process, but any code following the while loop is not executed. In fact, the process continues running for 10 seconds until the "abort VI timeout" is reached, at which point the VI stops. The "stop" terminal of the main while loop is wired to a "create control" "STOP" button on the front panel. Publishing or not publishing the "STOP" control during the I/O wizard process has no effect.
I'd like to do cleanup steps after the while loop terminates. Unfortunately the "Heat Exchanger" example has no code after the while loop to illustrate the concept.
What am I missing?
Thanks,
Mike

Hi Van - let me clarify my question...
I don't believe that the termination portion of the DSC "periodic I/O server wizard" actually works properly, or at least an example is needed of how to make it work.
It appears to me that the wizard functionality of "choosing the server termination method" might not work. Within the wizard, the two options are to abort the running server VI, or to choose a "while loop" to be forcefully-terminated with a standby timeout value to force a VI abort anyway, if the while loop does not exit.
I set up a simple server VI with one main while loop that does RS-232 I/O with a "running" beep on a 1 second timer. After the while loop is another small block of code that closes the serial port, and a different "terminating" beeper. When I run the VI interactively, both beeps work fine. When I use the wizard to turn it into a server and it is deployed to the SVE, the beeps begin normally. When I stop the SVE process via "remove process" in Variable Manager, the "running" beeps continue for another 10 seconds until the abort timeout occurs, even though with the wizard I specified the only while loop in the VI to be aborted.
The heat exchanger example works fine. Unfortunately it does not have any code following the while loop, so it doesn't shed any light on this issue. Ideally that example would be updated a little to show how to use the "while loop termination" feature.
Basically my request comes down to this: is there a way to actually make this work, or is it another in the list of bugs in 8.5.1?
Thanks,
Mike

Quit while loop in event structure

Hello,
I used event structure in my application and I would like to quit a while loop in an event structure when I pressed a control. But I have a problem because I'm in the event.
Do you have a solution.
Sam.
Attachments:
Problem.vi ‏34 KB

Hi,
connect a true constant to the While loop conditional terminal in the STOP event case.
See your example modified.
Good luck,
Alberto
Attachments:
Problem[2].vi ‏35 KB

Timed counter in a while loop without overlapping a second while loop

Hello,
Like you can see in attached file (waveform_counter.vi), I have a main while loop which makes a waveform graph and I would like to integer an inversed counter (from x seconds to 0) in some cases. I tried with a overlapped while loop, but obviously, when the counter works, the main loop breaks...
How can I make a sort of time counter without a loop ? I tried with the while loop iteration, every 100 iterations the counter decreases but I don't success.
Thanks for help.
Nathalie.
Attachments:
waveform_counter.zip ‏55 KB

Hello Nathalie:
Please see what I did in the expiration case.
Please advice if this is a possible solution.
Attachments:
waveform_graph 2.zip ‏41 KB

The demand of my application is that i can not replace for loop with a while loop.because i need fixed number of iterations and as far as i know fixed iterations could be only with possible with the for loop.

the demand of my application is that i can not replace for loop with a while loop.because i need fixed number of iterations and as far as i know fixed iterations could be only with possible with the for loop.
your recommended second option that i could add true/false case.
this true/false case must be inside the for loop or outside the for loop?if this case is inside the for
loop, how can i send stop command from outer while
loop?
more over do you have any example for this please?
thanks"

You can execute a fixed number of iterations using a while loop by comparing the iteration count to the number of iterations you want and wiring the output of that comparison (e.g. Less Than or Equal To) to the continue (or stop) terminal of your while loop. Which comparison you use depends on personal preference, where you wire the desired count and the interation count, and whether you're using the while loop as Continue if True or Stop if True.
Ben gave you step-by-step instructions in response to your previous question. Look here for Ben's response.
Ben's response looks pretty good and detailed to me. It certa
inly deserved better than a 1-star rating.

Iteration Speed issue when Indexing 3D array wried to a while-loop

Brief Description of my Program:
I am working on the real-time signal generation by using LabView and DAQmx (PCI-6110 card). My vi reads the big data file (typically 8MB txt file containing about 400,000 samples (complex double precision). Then, the signal is pre-processed and I end up with a huge 3D array to feed while-loop (typically 3D array dimension is N x 7 x M where N & M >> 7). Inside the loop, that 3D array is indexed and processed before the results are written to the DAQmx outputs. I have a speed issue when indexing the large 3D array (i.e, 3D array having a large sub-array size). My while-loop could not run fast enough to top-up the DAQmx AO buffer (at the output rate of 96kHz). It could run faster only if I use smaller 3D array (i.e, smaller-sized sub-arrays). I do not quite understand why the size of 3D sub-array affects the rate of looping although I am indexing same sub-array size at each iteration. I really appreciate your comments, advices and helps.
I include my 3D array format as a picture below.
Question on LabView:
How does indexing an 3D array which wires to the while-loop affect the speed of the loop iteration? I found that large dimension of sub-arrays in the 3D array slows down the iteration speed by comparing to indexing the same size of sub-array from smaller-sized sub-arrays of the 3D array to perform signal processing inside the while-loop. Why? Is there any other way of designing LabView Program to improve speed of iteration?
attachment:

Thank you all for your prompt replies and your interests. I am sorry about my attachment. But, I have now attached a jpg format image file as you suggested.
I had read the few papers on large data handling such as "LabVIEW Performance and Memory Management". Thus, I had already tried to avoid making unnecessary copies of data and growing arrays in my while-loop. I am not an expert on LabView, so I am not sure if the issues I have are just LabView fundamental limitations or there are any other ways to improve the iteration speed without reducing the input file size and DAQ output rate.
As you request, I also attach my top-level vi showing essential sections such as while-loop and its indexing. The attached file is as an image jpg format because the actual vi including Sub-VIs are as big as 3MB in total. I hope my attachment would be useful for anyone who would like to reply my question. If anyone would like to see my whole vi & llb files, I would be interesting to send it to you by an e-mail privately and thus please provide your e-mail address.
The dimension of my 3D array is N x 7 x M (Page x Row x Column), where N represents number of pages in 3D array, and M represents the size of 1D array. The file I am currently using forms 3D array of N = 28, & M = 10,731. Refering to the top-level vi picture I attached, my while-loop indexes each page per iteration and wrap-around. The sub-VI called "channel" inside the while-loop will further index its input (2D array) into seven of 1D arrays for other signal processsing. The output from that "channel" sub-VI is the superposition of those seven arrays. I hope my explaination is clear.
Attachement: 3Darray.jpg and MyVi.jpg
Kind Regards,
Shein
Attachments:
3Darray.jpg ‏30 KB
MyVI.jpg ‏87 KB

While loop and for loop condition terminal

Hello friends,
I am using labview 8.6. The condition terminal of the while loop and conditional for loop is behaving in just the opposite way.
When i wire a true to the condition terminal of my loop, the while loop continues to run when I click on run. when I wire a FALSE, it stops.
Is there any setting change that I have to make it to get it work properly.
Please suggest on this.
Thanks and regards,
Herok

Please do NOT attach .bmp images with the extension changed to .jpg to circumvent the forum filters!
Herok wrote:
I am sending you the VI. I am not sure if this would help you because only in 2 computers this behaviour is seen. In others, it works as it is supposed to work.
Whatever you are seeing must be due to some corruption or folding error. It all works fine here.
To make sure there are no hidden objects, simply press the cleanup button which would reveal any extra stuff (which is obviously not there). Does it fix itself if you click the termination terminal an even number of times? What if you remove the bad loop and create a new one?
Could it be you have some problems with the graphics card and the icon of the conditional terminal does not update correctly?
Whay happens if you connect a control instead of a diagram constant?
What is different on the computers where it acts incorrectly (different CPU (brand, model), #of cores, etc.)
LabVIEW Champion . Do more with less code and in less time .

Code golf: stop two while loops with guaranteed iteration ratio

Proposal
In the vein of the Perl tradition, I'd like to see if there's any interest in solving short programming puzzles in LabVIEW. Anyone can post a problem and define the rules for solving it.
Here's a beginning/intermediate question to whet your "palette".
Description
With one user-action, how would you stop two while loops such that the ratio of their iterations is the always the same? One concrete way to visualize this situation is in taking measurements: two instruments use the same timing source to take measurements, but second divides the clock down so that it is an integer factor slower than the first. For example, if the slower instrument is four times slower, then at the end of the VI, if the slower instrument takes 100 measurements, the faster instrument has taken 400.
Rules
You may only use vi.lib
You cannot include any other subVIs
Your solution must pass for loop1 interval as low as 25 ms
Template (attached in LabVIEW 2009)
If folks are interested in this, then let's figure out how to make future problems better. Please post your suggestions and critiques, but only if you also post a submission ;-)
Solved!
Go to Solution.
Attachments:
Multirate Loop Code Golf.vi ‏11 KB

Norbert_B wrote:
a) You work with an integer factor of speed. While this matches many application areas, there are still cases where the factor has to be floating point (e.g. 2.5). Additionally, the factor might "invert", so the master loop runs slower than the slave (factor 0.5 for instance).
It sounds like you're about to post another code golf question. If you think the problem scope is too small, you're welcome to fashion one to your taste. Thanks for volunteering :-D
Norbert_B wrote:
b) This example does not take into account that the hardware has to be synchronized with more accuracy than the software supplies (PXI?). If hardware synchronization is required, there are two possible ways:
- The factor can be included in the synchronization (using PLL for instance)
- The factor has to be software implemented by data reduction for the task running at the lower pace.
Hrm, maybe puzzles aren't really your thing after all. You are correct: I did not define every constraint that can lead to a provable best closed-form solution, but that does not prevent people from stating their assumptions and forming creative, well-reasoned, and still correct designs. I overlooked this reading of the description and neglected to add a statement that said solvers were free to add their own conditions. I will do so in the fugure :-)
If we choose the first of your suggestions, the VI must still retrieve the data at different rates. You can dedicate a loop for each instrument to decouple any jitter and latency introduced by their connectivity or internal operation; this adds some margin of safety when there is thread and driver contention. You can also implement a single counting loop like altenbach and forego the multiloop complexity.
Norbert_B wrote:
c) You don't state anything about "what happens with the data". Is this time consuming? Does it introduce additional delay in loop iterations? Is it OK to have data loss?
I don't know -- you decide, you disclose, and you solve :-)
In my specific situation, the measurements are time consuming and do add delay (each data "sample" is 5-20 megabytes), none can be lost, and the data must be available for others to analyze later. In addition, the amount of data is saturating the hard disk throughput. If a particular write takes too long, the instrument driver may overwrite a yet unfetched sample, which is unacceptable. I did not add these details to the problem discripton becuase they don't impact the puzzle.
I don't want to burden people with my situation and ask them to solve my problem: I want to encourage them to bring their intuition and experience to a discussion. This is the design process at its heart: understanding why and how constraints affect your decisions. If a person states the additional conditions they've assumed, readers can learn why, and more importantly, when a Notifier might be more desirable than an Occurance or a Queue more robust than a Data Value Reference.
The best NI-published advice for stopping multiple while loops (https://www.google.com/search?q=labview+stop+multiple+while+loops) is laughable (and is the "solution" in my template).
Would you care to re-approach and contribute to this puzzle? I suspect you have a lot to offer :-)

Iteration non sequencial with While Loop

I've a SubVi in while Loop. Iteration n+1 will execute when Iteration n finish.
Can I execute this SubVi in paralel (no sequencial)?
In Spanish:
Tengo una SubVi dentro de un bucle while. Pero este bucle actúa de forma secuencial. No se cargará la iteración n+1 hasta que la n acabe.
¿Cómo puedo hacer para que se ejecuten las iteraciones de forma no secuencial? Es decir, que no haya que espera a que acabe una para que se ejecute la siguiente.

Hello,
it is not possible. The while loop works as follows: 1) execute the code inside 2) check the ternimation condition 3) depending on that, continues with the following iteration or exit from the while loop. So, it is not possible what you are asking for.
Maybe you have to use two while loops.
Regards
rusC

Pause While Loop based on Iteration

I want to Pause a while loop based on a user imput and then continue if the input is changed. For example I want to have the loop run 5000 times then stop, later after it stops I change the number to 10,000, I want it to run only 5,000 more times. I want to be able to do this several times not just 2 times. I know how to get it to stop the first time but I dont know how to make it stop the second time without reseting the iteration count.
Thanks,
Billy
Solved!
Go to Solution.

You need to keep you own iteration count in shift registers. You might also want a way to reset that count.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Event structure in a while loop does an extra iteration

In this program, after the user has measured all the values, he or she will press a calibration complete button and the results of the measurement will be displayed. However when the program runs and this button is pressed, the event structure does one more iteration. Is there a way for the while loop to read the control before the event structure executes to prevent this?
p.s. I know that the wiring is probably a lot more complicated than it needs to be so if there is a better way to place values into a particular space in an array let me know
Thanks
Chris O.

Probably just a matter of the order of execution in your data flow.
Please post a VI so we can see what is going on now.
Never mind. You have since posted it. SMerucurio's suggestion of a separate event case for the other button should work fine.
Message Edited by Ravens Fan on 06-30-2008 01:20 PM
For putting an element into a specific location of an array, look at "Replace Array Subset". This should allow you to replace your groups of shift registers with a 1-D array since you are basically building 1-D arrays after your case structures anyway.
Message Edited by Ravens Fan on 06-30-2008 01:24 PM

While Loop - Iteration Terminal

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