Can't terminate while loop in producer/consumer
I have attached a simple vi that was constructed from the producer/consumer (events) template. In the vi I have set up a counter. I want to be able to terminate the counter when the stop button is pressed. This doesn't work as planned. The counter goes to its full count before the program stops. The vi does work as planned when run in highlight execution mode. Can't figure it out.
Thanks in advance.
Solved!
Go to Solution.
Attachments:
ProducerConsumerEvents 3.vi 14 KB
You can set the stop button to latch action and place it in the lower loop. No local variables needed.
The event will fire right away and the lower loop will reset the button once it's read. No race condition possible.
(Personally, I would probably redesign from scratch....)
Message Edited by altenbach on 08-10-2009 11:33 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
ProducerConsumerEvents 3MOD.vi 13 KB
ProducerConsumer.png 23 KB
Similar Messages
-
Timed Loop in Producer/Consumer Loop
Hello!
I have a producer/consumer loop LabVIEW program setup to allow me to properly capture images that are quite large (8MP) at approximately 14 frames per second (FPS). The program works great when the consumer loop is a 'while loop' (records at 14fps no problem), but I wanted to make it into a timed loop, so that I may vary the FPS as required. An oddity arises when I do this. Anywhere below 12fps, the loop works fine and the data is recorded properly. However, when I bump it up to 13fps, the consumer calculated FPS goes haywire and starts jumping between ~9 and ~13fps (data processing gets bogged?). When I set the required FPS to 14, the loop executes at a steady 7FPS maximum. Is there something I can do to rectify this situation?
I have attached my .VI
Thanks in advance!
Solved!
Go to Solution.
Attachments:
ProcessSplitJPG-FPS.vi 100 KBPalanski,
Are you using LabVIEW Real-Time? Timed loops in a windows OS don't really increase determinism more than a while loop with a wait until next multiple timer. Before you changed the producer consumer loop to include a while loop was the programming running correctly? You may also want to vuse the VI analyizer to see how long things are taking to run. I would leave the producer consumer loop in the traditional set up and change the FPS by controlling the wait timer, after benchmarking your code this should be done the same way as you have it for the timed loop
Sam S
Applications Engineer
National Instruments -
I want to add one Continuous function in Producer consumer event??
Hello,
producer consumer event vi is base example for me ,I have design my system according to it.
Now I am dealing with photo sensor in that its measure continuous data according to intensity of light,for continuous function I have make while structure for photo sensor but the problem is that I don't know how to add this while loop in producer consumer event ,if I add then its run continuously and then my operation is stuck there.
Will you please guide me that how can I add this continuous function in this structure so simultaneously I can do other function like pause reset..Etc...
Here in attachment I have attaché one example regarding to this in that I have add simply increment function in case structure and when I execute my vi then execution is stuck at while loop until it manually stop.
Thank you very much...
Attachments:
ProducerConsumerEvents 1.vi 15 KBHi AnkitRamani,
I made a simple example with a UI queue and a second producer which is pushing data into its own consumer, displaying the signal and its spectrum.
Maybe this is what u need.
Marco Brauner NIG
Attachments:
ProducerConsumerEventsData.vi 70 KB -
Can't we use while loop inside a fn
i am using a while loop inside a fn
it is showing error
the code is
while (a=1) loop
some condition
end loop;
the error is
PLS-00103: Encountered the symbol "WHILE" when expecting one of
the following:
* & = - + < / > at in is mod not rem then <an exponent (**)>
<> or != or ~= >= <= <> and or like between overlaps || year
DAY_
The symbol "*" was substituted for "WHILE" to continue.
PLS-00103: Encountered the symbol "LOOP" when expecting one of
the following:
. ( * % & = - + < / > at in is mod not rem then
<an exponent (**)> <> or != or ~= >= <= <> and or like
between ||
what is the errorIt looks like the OP misskeyed the assignment operator and got compilations errors, and from that assumed that you can't use WHILE loops in functions on a Tuesday.
Message was edited by:
William Robertson
I was thinking of his is it possible to increment a value in a function, though I suspect the problem is similar. -
Functinal global variable for producer - consumer architecture
Hi all,
I am using a Producer - consumer architecture for my data acquistion as in the belwo diagram.. at some time i am stuck insde the while loop continously acquiring data .. is there any way i use one stop button as a functional gloabl variable and stop inside (consumer while loop) as well as producer architecture....
Why i need this ?? so many design rules say that global variables are not a good idea...
Thanks in advance...FGVs will work fine for your application. You can also wire your error cluster to your stop button. Your producer loop should throw an error 1 when the stop button is pressed, which will in turn stop your consumer loop. But you would need a slightly different design for this. Your consumer loop is designed to not advance until the stop button is pressed. Instead of using and enum, you can use your producer loop to control the trigger to take a measurement. No need for the while loop in the consumer loop this way. You could set up your consumer loop to take a number of measurements, and then quit or take measurements for a certain amount of time. Either way, you can stop your while loop when it times out.
If you choose to stay with this design, a simple state machine archetecure might be better based on what I see.
Reese, (former CLAD, future CLD)
Some people call me the Space Cowboy!
Some call me the gangster of love.
Some people call me MoReese!
...I'm right here baby, right here, right here, right here at home -
Can I do while loop in a mapping. I know I can do this in process flow but can I do it in a mapping.
The OWB code generator produces a number of different code modes including set based SQL and various modes of row based code. In the row based code there are essentially (implicit) loops over the cursors, so there are implicit loops that you can do stuff, depends on what you are after.
Cheers
David -
How to stop a while loop in LabVIEW from a C program
How to stop a while loop in LabVIEW from a C code
hi
I think by creating dll you can stop the while loop from your C program.For that you just create dll (Dynamic Link Library) for the VI which has that while loop.
Anyway can u please explain ur requirement clearly. -
I have always seen and used CURSORs with WHILE loops.
I am looking for great examples where CURSORs are used without WHILE loops. Thanks.
Kalman Toth Database & OLAP Architect
SQL Server 2014 Database Design
New Book / Kindle: Beginner Database Design & SQL Programming Using Microsoft SQL Server 2014You can implement any logic that you want. We need to know what is your needs in order to post a code. If all you need is to make a loop on all the SET in the same way while do, without using while loop then here is a simple example. You can implement any
WHILE loop with IF condition and GOTO. This is only for sake of discussion and I will not use this code in production :-)
use AdventureWorks2014
GO
SET NOCOUNT ON;
DECLARE @vendor_name nvarchar(50)
DECLARE vendor_cursor CURSOR SCROLL FOR
SELECT Name
FROM Purchasing.Vendor
WHERE PreferredVendorStatus = 1
OPEN vendor_cursor
PRINT '******** Using While loop ********'
FETCH NEXT FROM vendor_cursor INTO @vendor_name
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT @vendor_name
FETCH NEXT FROM vendor_cursor INTO @vendor_name
END
CLOSE vendor_cursor;
OPEN vendor_cursor
PRINT '******** Without Using While loop! ********'
FETCH NEXT FROM vendor_cursor INTO @vendor_name
Starting_Read_From_Cursor:
-- Using If with GO TO
IF @@FETCH_STATUS = 0 BEGIN
PRINT @vendor_name
FETCH NEXT FROM vendor_cursor INTO @vendor_name
GOTO Starting_Read_From_Cursor
END
CLOSE vendor_cursor;
DEALLOCATE vendor_cursor;
I hope this useful :-)
I am not sure for what, at the moment
[Personal Site] [Blog] [Facebook] -
Can anyone tell me what's wrong with my queue or producer consumer loop?
A Labview engineer helped me with the overall structure of my program, necessitated by the fast data sample rate and post processing requirements. He recommended the producer/consumer loop and using one of the example files (Cont Acq graph voltage - int clk) to do the actual data acquistion. So I put together the loop and go my two channels of data acq going in the producer loop. However, nothing's getting picked up in the consumer loop and none of my data gets displayed over there.
Anyone care to take a look at it and let me know what I'm doing wrong?
Solved!
Go to Solution.
Attachments:
P-C Yanmar Program.vi 296 KBYour Enque Element should be inside the while loop where you aquire the data. As it is now, the data has to stop being aquired before you send the last set of aquired data.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines -
I've attached a sample VI that I just cannot figure out how to get working the way that I want. I've labeled the some sections with black-on-yellow text boxes for clarity during the description that follows in the next few sentences. Here's what I want:
1) overall -- i'm intend for this to be a subVI that will do data acquisition and write the data to a file. I want it to use a producer/consumer approach. The producer construct is the 'parallel for loop' that runs an exact number of times depending on user input (which will come from the mainVI that is not included). For now I've wired a 1-D array w/ 2 elements as a test case. During the producer loop, the data is acquired and put into a queue to be delt with in the consumer loop (for now, i just add a random number to the queue).
2) the consumer construct is the 'parallel while loop'. It will dequeue elements and write them to a file. I want this to keep running continuously and parallel until two conditions are met.
i. the for loop has finished execution
ii. the queue is empty.
when the conditions are met, the while loop will exit, close the queue, and the subVI will finish. (and return stuff to mainVI that i can deal with on my own)
Here's the problems.
1) in the "parallel for loop" I have a flat sequence structure.. I haven't had time to incorporate some data dependency into these two sequential sections, but basically, I just care that the "inner while loop" condition is met before the data is collected and queued. I think I can do this on my own, but if you have suggestions, I'm interested.
2) I can easily get the outer for and while loops to run sequentially, but I want them to run in parallel. My reasoning for this is that that I anticipate the two tasks taking very different amounts of time. .. basically, I want the while loop to just keep polling the queue to get everything out of it (or I suppose I could somehow use notifiers - suggestions welcome)... the thing is, this loop will probably run faster than the for loop, so just checking to see that the queue is empty will not work... I need to meet the additional condition that nothing else will be placed in the queue - and this condition is met when the for loop is complete. basically, I just can't figure out how to do this.
3) for now, I've placed a simple stop button in the 'parallel while loop', but I must be missing something fundamental here, because the stop button is totally unresponsive. i.e. - when I press it, it stays depressed, and nothing happens.
suggestions are totally welcome!
thanks,
-Z
Attachments:
daq01v1.vi 59 KBI'd actually like to add a little more, since I thought about it a bit and I'm still not quite certain I understand the sequence of events...
altenbach wrote:
zskillz wrote:
So i read a bit more about the 'dequeue element' function, and as I understand it, since there is no timeout wired to the dequeue element function, it will wait forever, thus the race condition I suggested above can never happen!
Yes, you got it!
As I've thought about it a bit more, there's a few things that surprise me... first, the reason the 'dequeue element while loop' errors is not because there's nothing in the queue, it's becaues the queue has been released and it's trying to access that released queue... However the problem I have is this --- Even though there's no timeout wired to the dequeue element, I still would think that the while loop that contains it would continue to run at whatever pace it wanted -- and as i said before.. most of the time, it would find that there is nothing to dequeue, but once in a while, something is there. however, it seems that this loop only runs when something has been enqueued. the reason I say this is illustrated in the next code sample MODv2 that's attached below. I've added a stop button to the "queue size while loop" so the program runs until that is pressed. I've also added a simple conditional in the "dequeue while loop" that generates a random number if it a button is pressed... but this button is totally non-responsive... which means to me that the "dequeue while loop" isn't actually continuously running, but only when an element is added to the queue. this still seems almost like the 'dequeue while loop" waits for a notifier from the queue telling it to run. can you explain this to me? because it is different from what I expect to be happening.
rasputin wrote:
I tried to open your VIs but it doesn't work. LV
is launched, the dialog box (new, open, configure...) opens and then...
nothing. Not even an error message. I guess it isn't a problem of LV
version or a dialog box would appear saying this. Could you, please,
send a image of the code?
Thanks,
Hi Rasputin, I'm using LV8. I assume that was your problem, but who knows. I've attached a pic of of altenbach's solution since it's what I needed.
thanks
-Z
Message Edited by zskillz on 10-20-2006 11:49 AM
Attachments:
daq01v1MODv2.vi 63 KB
daq01v1MODpic.JPG 116 KB -
Hi,
I'm trying to figure out the best way to implement a producer/consumer architecture. I'm hoping there is something simple that I don't understand.
I have a state machine executing in it's while loop, doing things like saving and processing data. The data is being passed through a queue from a separate while loop. I'm currently starting that producer loop using occurrences, and I can stop it with a local variable.
What I can't figure out is how to restart that loop from within the state machine? In essence, I'd like to have a switch that says "Collect Data" and it will turn the producer while loop on and off but leave the main program running in the meantime.
Thanks for any suggestions.
mikeBasically, i find producer/consumer architectures where the consumer creates "commands" (Edit: which do more than simple notification tasks) for the producer quite absurd.
I would switch to a three loop architecture:
Producer A is responsible for UI display/control. It feeds Consumer A which is infact Producer B.
Producer B (aka Consumer A) is the DAQ consumer. It will acquire data due to the settings passed by Producer A. The DAQ data will be passed to Consumer B.
Consumer B handles the data passed by Producer B. If necessary, it can create custom user events in order to notify Producer A about certain situations in the software.
An approach with an Action Engine can be similar in regard to functionality, has its own advantages and disadantages.
hope this helps,
Norbert
Message Edited by Norbert B on 01-14-2010 12:13 PM
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it. -
Can 2 while loops work at the same time?
I have two while loops in my program; one reads data and the other does nothing until I hit stop on the first one. I want the first one to always run and the second to run off of the time constraint I have for it when I hit the start button. I am using a DAQ and transfering data from one while loop to the other. See attached file.
Main questions:
How to attach the start button?
How to get the second loop to work with the first?
Thank you
Solved!
Go to Solution.
Attachments:
2whlloopprgrm.vi 299 KBYour problem is that the loops have a data dependency. If you want to run both loops at the same time, they can't have any wires running from one to the other. Look into the Producer/Consumer architecture. It uses queues to send data from one loop to the other.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines -
sir i have given lot of effort but i am not able to solve my problem either with notifiers or with occurence fn,probably i do not know how to use these synchronisation tools.
sir i am using datasocket read ,i am communicating with java but my problem is that bcz im using while loop to see if value has changed my labview consumes all the processors time ,sir i want a event like thing so that while loop is not in continuous loopHi Sam,
I want to pass along a couple of tips that will get you more and better response on this list.
1) There is an un-written rule that says more "stars" is better than just one star. Giving a one star rating will probably eliminate that responder from individuals that are willing to anser your question.
2) If someone gives you an answer that meets your needs, reply to that answer and say that it worked.
3) If someone suggests that you look at an example, DO IT! LV comes with a wonderful set of examples that demonstate almost all of the core functionality of LV. Familiarity with all of the LV examples will get you through about 80% of the Certified LabVIEW Developer exam.
4) If you have a question first search the examples for something tha
t may help you. If you can not find an example that is exactly what you want, find one that is close and post a question along the lines of "I want to do something similar to example X, how can I modify it to do Y".
5) Some of the greatest LabVIEW minds offer there services and advice for free on this exchange. If you treat them good, they can get you through almost every challenge that can be encountered in LV.
6) If English is not your native language, post your question in the language you favor. There is probably someone around that can help. "We're big, we're bad, we're international!"
Trying to help,
Welcome to the forum!
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction -
I'm attempting to create a calibration program, using the printer port, and a Vernier Serial Box by modifying a calibration program designed for the serial box.
There are six calibration points, and to collect them, I have it controlled by while loops so that the numbers are taken when a button is pushed, and this is inside a sequence structure so that I can get the six different points. I feed these numbers into two different arrays (for x and y values) and then try to use the linear coefficient analysis on these points, but the values for the slope and intercepts it returns are not correc
t.
If I cut out the array and coefficient analysis, and feed the same numbers in directly without the while loop and sequence structures, it produces the proper values... I don't know why the numbers it is producing are different, and I'd really like to know.
Thanks,
Karinne.I would use a data manager sub-vi that would be called by each from of the sequence structure that produced a data point. The data manager sub-vi could auto append new items or could place items in a specific entry of an array. Later on when you want to calculate the linear fit, call the sub-vi to return the array of values.
Stu -
I have a Producer consumer loop that is reading in data from a Excel File call sample1. There is a third party software that constantly writes data to the same excel file Sample1 every _ amount of seconds. Every time the Third party software writes it will over write the excel file data. So it may only be 5 columns and 3 rows.
1. I need to make sure that there is not a conflict when the Third party software has the file locked to read and Labview is trying to read.
2. I need to make sure that if labview isn't reading and reading before the Third party software writes so basically i need some way of checking labview isnt reading the same data twice i need to make sure the file has been updated before it tries to read again. The problem comes in when you can't regulate the time that the third party software reads.
Solved!
Go to Solution.
Attachments:
VI snippet (2).png 123 KBI've had to write code for similiar applications. It is tricky.
Have a look at the .NET FileSystemWatcher.Changed Event. This might be a good way to monitor what is happening with the file.
Take a look at this post: http://forums.ni.com/t5/LabVIEW/My-First-Nugget-Directory-Changed-Event/m-p/1407552/highlight/true#M...
"There is a God shaped vacuum in the heart of every man which cannot be filled by any created thing, but only by God, the Creator, made known through Jesus." - Blaise Pascal
Maybe you are looking for
-
yes, so i connect to my wifi at home, my brothers iphone works fine, but my ipod touch 1st gen dosent conect. it connects but when i go on safari it dosent work, it says" connecting" with the circle loading thing. plz help< o and my router is fine be
-
what will i do? i dont have prob with my net connection.
-
How do I upgrade my operating system on OSX 10.2.8
I'm trying to upgrade my computer so I can download and use the new itunes. I have looked in the apple menu for the command "update latest softwear" but on my version it doesn't exist and the only option is Get OS X softwear. This takes me to the App
-
Can not stream BBC radio 4. Why can't I get Adobe Flash Player?
Just taken delivery of iPad2.
-
PO Output determination using Plant as a condition
Hi All, I want to use PLANT (werks) as a condition in PO output determination. How do I do that? Basically, I want to be able to send ORDERS IDoc only when the Plant is a certain value. Where can I check the plant information before sending the outpu