Slow Dataflow processing in While Loop

Hi,
I'm processing XML files with BODS XI 3.2 12.2.2.0 in a Workflow that uses a while loop and scripts to get the next file.
(Approach like in: http://wiki.sdn.sap.com/wiki/display/BOBJ/SelectiveReadingand+Postprocessing)
Each Dataflow process takes about 1.5 sec, but in each loop there is a "waiting time" of 5 seconds beween the end of the dataflow and the finalizing script that follows it:
7364     2560     DATAFLOW     30.03.2011 14:13:49     Data flow <DF_UC5_ImportXML> is completed successfully.
7364     2560     DATAFLOW     30.03.2011 14:13:49     Process to execute data flow <DF_UC5_ImportXML> is completed.
1156     5300     PRINTFN     30.03.2011 14:13:54     exec...
1156     5300     PRINTFN     30.03.2011 14:13:54     wait_for_file...
(The print commands are the first commands in th escript following the dataflow)
Does anybody know what's happening in these 5 seconds or how I could find out and optimize it?
Thanks for your help!
Martin

What happens before a dataflow starts processing?
We read the repo for the dataflow definitions
We optimize the the dataflow
We connect to sources
We connect to targets
We connect and cache lookup tables if defined
And at the end all database sessions are disconnected, image memory released etc.
Or in other words - don't build a dataflow processing a handful of rows only. If anything, that's more aligned to realtime dataflows.

Similar Messages

Waveform charts slowed down control system while loop

Hi
In my application, I have control system which i acquire data, process and output the result. I placed some waveform charts in the while loop where i acquire data, process and output. This made while loop to miss data points( late). Is this because waveform charts store data as time passes?

Waveform charts store data in a history buffer of configurable size. You can change it to a smaller number.
What is the size of the history buffer?
How many charts are you updating in your loop?
What else is happening in your loop?
How are you updating them (wire, local variable, value property, etc).
How fast is your loop rate?
Are your plots simple (thin lines) or fancy (e.g. large dots and thick lines)?
Is autoscaling on or off?
Are the charts set to "synchronous display" by accident?
How many traces are on your chart?
What is your LabVIEW version?
What is your OS?
Do you have overlapping elements on the front panel?
Could you attach a simplified version of your code so we have a better idea what you're actually doing?
LabVIEW Champion . Do more with less code and in less time .

Calling Synchronous process in a loop

Hi
I am facing a problem while I am tring to call Synchronous process in a loop. I am having a parent process that fetch batches numbers (list of batches) and loop for each of them and call a child Synchronous process to do some activity.
the issue here is that the output variable on the process is taking the value that returns from the first batch call and keep repeating it for all the rest batches. I tried to initialize it to null every time I am entring the loop but strangly it has been overrided with the output variable of the first batch and then for the rest it just initialized to null and not had been overriden.
any body face this before or knows about it
thanks and best regards,
Baraa

This is Arun (working with Baraa in same Company)
Let me eloborate the situvation
Facing problem while I call a Sync process from an Async process using while loop.
When I call sync child multiple times from a parent process using a While loop the response msg from child process is not correct.
Meaning for instance let say
Parent process : P
Child processes : C1, C2, C3 (assuming the loop goes for three iteration)
The expected response msg of the individual process where
C1: 10000
C2: 999
C3 : (null)
But when I go through the audit of the parent process I could see all responses as 10000, meaning the response of the child process is not getting reflected in Parent process correctly
Whereas when I inspect individual child process response; I could see the correct values.
Note: I am using End Point Reference technique to call the child process
Any Idea.
Requirement:
Parameter: Source System Name
(this parameter decides which child to call, basically this will be the SERVICE on WSDL pointing to the child process)
A parent Async process has to call a Sync child process “n” number of times (“n” get derived at run time) WHILE loop
The parent will decide which child process to call at runtime (Dynamic call using EndPointReference)
Some thing like below:
<Set END POINT REFERENCE>
<WHILE>
Invoke Child (synchronize process)
<END LOOP>

Slow performance of application with 2 while-loops

I made an application with one while-loop addressing several FP devices which runs as expected in a FP-2015. Loop time is 100 ms.
If I add another while-loop with a timer, the performance is very slow. How come?

I tried to do a simular thing, but I did not notice a performance decrease. However it might be possible that this happens. For example, if you are calling a time critical vi in the second while loop, it will lock all other processes until it is finished. Or maybe you are calling a shared resource (allocate an array, access to a file, using a mutex) that the other loop holds. Until the shared resource is released the first while loop must wait before it can access that resource (memory, file, etc.).
Without looking at the source code it will be hard to say what is causing it. I recommend to remove part by part subVI's from the second loop, to debug where the problem exists. If you want I can have a look at the code, please reply to this thread.
ErikvH
A
pplications Engineering
National Instruments
Attachments:
Digital_Output.vi ‏56 KB

How I break while loop activity in BPEL process

Hi Guys,
I want to do a polling action in my bpel process, I put in the polling code in while activity ,
I try two way to do the break :
1. use the Flow activity , one sequence for while loop activity , one sequence for timeout flow , put waiting activity in it ,config timeout ... but Flow activity complete only when all branch complete . so it seems there is no way to break Flow from one branch.
2.use onalarm branch of scope ... put while activity code in a scope activity , create onalarm branch for this scope ,config the timeout time ... but onalarm branch can't bypass the scope sequence...
Any advice ?
Thanks
Kevin
Edited by: kyi on Oct 29, 2009 1:01 PM

The on-alarm branch of the scope should work.
Maybe not so neat but you could try to do a scope with a flow within that. Put in one of the flow-branches a wait. After the wait throw an exception.
You can catch that exception in a catch branch of the surrounding scope.
Regards,
Martien

Running java process in a while loop using Runtime.exec() hangs on solaris

I'm writting a multithreaded application in which I'll be starting multiple instances of "AppStartThread" class (given below). If I start only one instance of "AppStartThread", it is working fine. But if I start more than one instance of "AppStartThread", one of the threads hangs after some time (occasionaly). But other threads are working fine.
I have the following questions:
1. Is there any problem with starting a Thread inside another thread?. Here I'm executing the process in a while loop.
2. Other thing i noticed is the Thread is hanging after completing the process ("java ExecuteProcess"). But the P.waitFor() is not coming out.
3. Is it bcoz of the same problem as given in Bug ID : 4098442 ?.
4. Also java 1.2.2 documentation says:
"Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, and even deadlock. "
I'm running this on sun Solaris/java 1.2.2 standard edition. If any of you have experienced the same problem please help me out.
Will the same problem can happen on java 1.2.2 enterprise edition.?
class AppStartThread implements Runnable
public void run()
while(true)
try
Process P=Runtime.getRuntime().exec("java ExecuteProcess");
P.waitFor();
System.out.println("after executing application.");
P.destroy();
P = null;
System.gc();
catch(java.io.IOException io)
System.out.println("Could not execute application - IOException " + io);
catch(java.lang.InterruptedException ip)
System.out.println("Could not execute application - InterruptedException" + ip);
catch (Exception e)
System.out.println("Could not execute application -" + e.getMessage());

I'm writting a multithreaded application in which I'll
be starting multiple instances of "AppStartThread"
class (given below). If I start only one instance of
"AppStartThread", it is working fine. But if I start
more than one instance of "AppStartThread", one of the
threads hangs after some time (occasionaly). But other
threads are working fine.
I have the following questions:
1. Is there any problem with starting a Thread inside
another thread?. Here I'm executing the process in a
while loop.Of course this is OK, as your code is always being run by one thread or another. And no, it doesn't depend on which thread is starting threads.
2. Other thing i noticed is the Thread is hanging
after completing the process ("java ExecuteProcess").
But the P.waitFor() is not coming out.This is a vital clue. Is the process started by the Runtime.exec() actually completing or does the ps command still show that it is running?
3. Is it bcoz of the same problem as given in Bug ID :
4098442 ?.
4. Also java 1.2.2 documentation says:
"Because some native platforms only provide limited
ed buffer size for standard input and output streams,
failure to promptly write the input stream or read the
output stream of the subprocess may cause the
subprocess to block, and even deadlock. "These two are really the same thing (4098442 is not really a bug due to the reasons explained in the doc). If the program that you are exec'ing produces very much output, it is possible that the buffers to stdout and stderr are filling preventing your program from continuing. On Windows platforms, this buffer size is quite small (hundreds of characters) while (if I recall) on Solaris it is somewhat larger. However, I have seent his behavior causing problem on Solaris 8 in my own systems.
I once hit this problem when I was 'sure' that I was emitting no output due to an exception being thrown that I wasn't even aware of - the stack trace was more than enough to fill the output buffer and cause the deadlock.
You have several options. One, you could replace the System.out and System.err with PrintStream's backed up by (ie. on top of) BufferedOutputStream's that have large buffers (multi-K) that in turn are backed up by the original out and err PrintStream's. You would use System.setErr() and System.setOut() very early (static initializer block) in the startup of your class. The problem is that you are still at the mercy of code that may call flush() on these streams. I suppose you could implement your own FilterOutputStream to eat any flush requests...
Another solution if you just don't care about the output is to replace System.out and System.err with PrintStreams that write to /dev/nul. This is really easy and efficient.
The other tried and true approach is to start two threads in the main process each time you start a process. These will simply consume anything that is emitted through the stdout and stderr pipes. These would die when the streams close (i.e. when the process exits). Not pretty, but it works. I'd be worried about the overhead of two additional threads per external process except that processes have such huge overhead (considering you are starting a JVM) that it just won't matter. And it's not like the CPU is going to get hit much.
If you do this frequently in your program you might consider using a worker thread pool (see Doug Lea's Executor class) to avoid creating a lot of fairly short-lived threads. But this is probably over-optimizing.
Chuck

For loop or while loop in process flow

Hi,
Is it possible to use a table as driver for a loop ?
I want to loop (the number of records in my table ) times and use the value of a certain column as parameter in my loop.
Thanks in advance
Carolineb

Carolineb,
I think this is possible - develop three PL/SQL-procedures
1) first procedure PR_GET_LAST_VAL - with one OUT parameter for getting ID of last record from your table (for example select max(id) from your_table)
2) second procedure PR_GET_FIRST_VAL - with one OUT parameter for getting ID of first record
3) third procedure PR_GET_NEXT_VAL - with one IN/OUT parameter for getting ID of next record (for example select min(id) from your_table where id>P_VALUE , where P_VALUE is a procedure parameter)
4) define two variable for process - V_CUURENT (loop variable which will be chaned with third procedure) and V_LAST_VALUE
5) in process flow before LOOP operator insert procedures PR_GET_FIRST_VAL and PR_GET_LAST_VAL and bind parameters to variables V_CUURENT and V_LAST_VALUE respectively
6) define condition for LOOP operator as V_CUURENT <= V_LAST_VALUE
7) in body of LOOP operator insert procedure PR_GET_NEXT_VAL and bind parameter to variable V_CUURENT
Hope my idea is clear.
Regards
Oleg

Simulataneous While Loop Processing

Hi,
I have an application that is based on an Event Structure. When a start button is pressed an even is triggered (START Button) that contains a while loop. The while loop runs a test for a specified time. Whilst this loop is running all other functionality within the application is disabled. I need to be able to click on other tabs and trigger other events whilst this loop within the event structure is running.
I think I need to be running parallel loops or something but I dont see how I can do that and still have the event triggering functionality.
I have attached my working vi in hope that it highlights what I mean. Any advice would be gratefully received :-)
Liz
Attachments:
IDTS Working Extract Data.vi ‏333 KB

You have about 90% too much code!
Does it really take 2 "delete from array" followed by "index array" to simulate an "array subset"???
In the "load" event, you have two consecutive loops, the first creating an array of indices that you then autoindex out in the next loop and throw away later. I guess one loop would be enough, simply wiring to [i].
You are not using any terminals, but only value property nodes.
You are constanty growing and shrinking arrays in shift registers.
It is a very bad idea in general to trap code in a while loop inside an event structure.
First of all, don't use "lock front panel until event completes", but the overall problem is much deeper. You could probably use the outer loop and the timeout event for the "start" part. See e.g. http://forums.ni.com/ni/board/message?board.id=170&view=by_date_ascending&message.id=224817#M224817
LabVIEW Champion . Do more with less code and in less time .

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

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 :-)

While loop running too fast

I have a while loop that is writing globals into shift registers. When the loop finishes i write these shift registers to a 2d Global array. Everything works great, my problem is that i am writing about 14000 readings/sec into the shift registers with a wait of 0 in wait until next multiple. File is way too big. If i change wait to 1, i get 500 readings/sec, too small. I need a way to slow this loop down, or put a delay in that is less than 1ms. Any help is Greatly Appreciated.
Thanks
Mike

Pincpanter has some good ideas and is probably what you will need to do.
Keep in mind that tuning this way is very system dependant. Changes in processor, processor speed, memory access speed, OS processes running, etc. will all affect the amount of time that LabVIEW takes and therfore takes a lot of tuning for each system.
I just wish I had an even better answer, but I don't.
Bob Young
Bob Young - Test Engineer - Lapsed Certified LabVIEW Developer
DISTek Integration, Inc. - NI Alliance Member
mailto:[email protected]

Can not pass data after while loop

Hello.
I have created a VI for my experiment and am having problem passing data outside a while loop to save on an excel file. The VI needs to first move a probe radially, take data at 1mm increment, then move axially, take data radially at 1mm increment, then move to the next axial position and repeat. It would then export these data to an excel file. The VI is a little complicated but it's the only way I know how to make it for our experiment. I have tested it and all the motion works correctly, however I can not get it to pass the data after the last while loop on the far right of the VI where I have put the arrows (Please see the attached VI ). Is it because I'm using too many sequence, case, and while loops? If so, what other ways can I use to make it export data to the excel file?
Any help would be appreciated.
Thank you,
Max
Attachments:
B.Dot.Probe.Exp.vi ‏66 KB

Ummmm .... gee, I'm not even sure where to begin with this one. Your VI is well .... ummmm... You have straight wires! That's always nice to see. As for everything else. Well... Your fundamental problem is lack of understanding of dataflow programming. What you've created is a text program. It would look fantastic in C. In LabVIEW it makes my heart break. For a direct answer to your question: Data will not show up outside a while loop until the while loop has completed. This means your most likely problem is that the conditions to stop that specific loop are not being met. As for what the problem is, I don't even want to start debugging this code. Of course, one way to pass data outside of loops is with local variables, and hey, you seem to be having so much fun with those, what's one more?
This may sound harsh, and perhaps be somewhat insulting, but the brutal truth is that what I would personally do is to throw it out and to start using a good architecture like a state machine. This kind of framework is easy to code, easy to modify, and easy to debug. All qualities that your code seems to lack.
Message Edited by smercurio_fc on 08-17-2009 10:00 PM

Problem with DAQ in while loop and Graphs

Hello,
I'm new here so I apologize if I posted this on the wrong board
This is my "situation":
I need to make a simple PID controller which takes information (process variable) from an outside source (a NI's DAC connected through the USB port ) which is accomplished using NI-DAQ as an input, and the PID's output goes to the second NI-DAQ which is also connected using DAC to an actuator which in my case regulates the air pressure. (VI attached)
My problem is the following.
Both of the NI-DAQ I placed using DAQ Assist, require to be in a while loop.
-If I place them in separate loops, I have the problem of passing information between the Input NI-DAQ and the PID, and also between the PID and the Output NI-DAQ.
-If I place them both in one big loop, an error occurs saying that the selected buffer size is too small (Error -200609).
The timing settings for the DAQ's N samples, 100 samples to read at the rate of 1k (I also tried with Continuous samples and many different combinations of Samples to Read an Rate but without success).
Should I wire them with the same dt(s)?
The other thing I need to do (I'm also writing it here in order not to open new topics) is show the following 3 signals on a Graph (process variable (dynamic data type)(range 4mA - 20mA), PID output (double)(range 4mA - 20mA), and the Set Point (double)(range 0 to inf))
Firstly, is it possible to show the first two on a scale from 0 to 100 without changing the PID's output which needs to be 4-20?
Secondly, which graph should I use if I have different data types? (I tried the Waveform Chart, and succeeded in showing the first two; the third just messes everything up)
I would also have to make a legend explaining which signal is which (I see that this is possible with the Mixed Signal Graph).
I know this is probably too much to ask, but I'd be grateful for any help
Thank you in advance
Attachments:
PID while.vi ‏100 KB

My problem is the following. Both of the NI-DAQ I placed using DAQ Assist, require to be in a while loop.
-If
I place them in separate loops, I have the problem of passing
information between the Input NI-DAQ and the PID, and also between the
PID and the Output NI-DAQ.
This is the best option---Use QUEUE or Functional global or something else to tranfer the data to and fro
How do I make that QUEUE or Functional global?
-If I place them both in one big loop, an error occurs saying that the selected buffer size is too small (Error -200609).
Have
you tried increasing the buffer? Is the acquisition happening
parallelly (means to say the first DAQ not wired (error terminal) to
second DAQ)
Well the buffer is, at least how I understood it, the option Number of Samples when in Continuous Samples mode. Concerning the parallel acquisition, do you mean I should wire the error ports of both of the DAQs?

How can I update cluster items from inside a while loop that does not contain the cluster?

I have a VI that contains front panel clusters and two while loops. The main cluster contains items such as a doubles "distance" and "stepsize" and boolean "step" (a whole buch of this type stuff). The first loop contains an event structure to detect front panel changes and the second contains code and sub VIs to perform operations based on detected events.
The operator can enter data into either double or click the boolean. If distance is changed the second loop does what is required to process the change. The same happens with stepsize. If step is clicked the ±stepsize value is added to distance and the result is processed. In each case the front panel should track the result of the input and subsequent processing.
Because the clusters are outside the while loop, they are not updated unless I click 'highlight execution' which seems to allow updating each time the execution highlight is updated. There are other issues if I move the clusters into one of the loops.
I've tried referencing the clusters and using local variables and nothing works. It looks like overkill to use shared variables for this.
Any ideas would be greatly appreciated.
Thanks,
Frank

Hi Ben,
Thank you for the response. I followed the link and tried reading everything you posted on AEs but I'm afraid that I didn't understand it all. It seems that each AE example had a single input and a single output (e.g. a double). Is this the case?
What I have is a couple of front panel clusters containing (approximately) 18 control doubles, 8 indicator doubles, 5 boolean radio button constructs and 26 boolean control discretes. I clusterized it to make it readable. In addition I'll eventually have a cluster of task references for hardware handles.
All I want to do is update the front panel values like I would do in a C, VB or any other language. I've tried referencing the cluster and using the reference from inside the loops. I've tied using local variables. Neither works. I'm experimenting with globals but it seems that I have to construct the front panel in the gloabal and then I wouldn't know how to repoduce that on the front panel of the main VI. Sometimes it seems that more time is spent getting around Labview constructs than benefitting from them.
I hope the 'Add Attachment' function actuals puts a copy of the VI here and not a link to it.
Thanks again for the suggestion,
Frank
Attachments:
Front Panel Reference.vi ‏33 KB

How to out from infinite while loop in sub VI

Dear Sir,
how to out from infinite while loop in sub VI from main VI
attached photo for solution but I can't understand it and i can't find the function in photo
please help
Attachments:
stop_subVI_frm_main.JPG ‏36 KB

Asking how to get out of an infinite loop is like asking how to find the end of a circle. I'm not trying to be sarcastic but by definition, if there is a way out of the loop, then it is not infinite. I think what you are asking is how to avoid creating an infinite loop. Is there something about the suggestions you have been given that you do not like? My favorite suggestion is the notifier but maybe you just need an example. Turn on context help and read about the notifier functions in the code below.
This is your top level VI
And this is your subVI
If this seems too complex then a global variable will work too. But what seems simpler can cause much more complex bugs. You can code fast and spend lots of time debugging or you can code slow and spend less time debugging. Personally I perfer writing productive code than looking for bugs any time.
=====================
LabVIEW 2012

Slow Dataflow processing in While Loop

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