Simulation & Control with local variables

Why can I use a local variable in a simulation loop, but not in a simulation sub-VI?
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A little backstory which I should have given when I asked the question.
I have a simulation of an engine and I want to enable/disable the engine clutch. Since there are conditions on changing the clutch state I was using local variables when I developed the engine simulation in a simulation loop. After I had fixed the bugs I tried to transfer the contents of the simulation loop into a simulation subVI for use in my main project. I was unable to transfer the simulator because I had local variables in the engine simulation.
I think I understand that I can't use a local variable in a simulation subVI because there's no front panel due to the way a subVI is called.
Thank you for the help in understanding this better.

Similar Messages

How to set multple values in cluster with local variable?

Hello all,
Ok, I've made my way through Labview for everyone, and have some basic concepts down. I can see with a cluster, if acting directly upon it, you can unbundle, change values, rebundle, etc.
I'm trying something a bit more complex...and just not sure how to get started on this.
I have a drop down menu ring. I have set this up as a typedef, with 4 values. I have used this typedef 7 times, plus some LED bools, in a cluster. I have made this cluster a typedef.
So, in my main vi I"m starting to design, I've set up an example posted here....and in it, I have two instantiations of the cluster typedef, Left Selector and Right Selector.
I have dropped into this vi, a copy of the menu ring typedef (same typedef as in the clusters, same values)....called reset all tubes.
I'm trying now, to figure out how, with an event on the change of value for 'reset all tubes'....that I can start with the left selector, and change all the tubes (these are the menu ring selector) to the same value as what has been selected with the 'reset all tubes' menu ring.
I've created a local variable for the left selector. It is set to read values. (I'll be doing the same with the right one too, but just starting with the left).
In examples I've seen where directly accessing a cluster, you could unbundle the cluster...loop through and change the values...maybe pull out all of the 'tubes' into an array and move through that to update the values. And when you bundle or unbundle the cluster...you can see the values, etc, when you stretch them out on the block diagram.
With the local variable..I can't see to 'stretch' it out like I was expecting..so I can access the values for the 'tubes'...and set them all to the value of the 'reset all tubes' ring menu value.
Can someone put me on the path on the best way to do this....or is there a structure of component I'm missing here ? Am I on the right track to begin with here?
This would seem pretty basic to me, but I'm just missing something here on how to start...
Thank you in advance,
cayenne
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Attachments:
example_select_dropdown.ctl ‏5 KB
public_selector_cluster.ctl ‏6 KB
laptop_test_public.vi ‏12 KB

nathand wrote:
You can't do this with a for loop the way the cluster is structured, but why make it so complicated? Just bundle the new value into the cluster as shown below:
If you do want to use a for loop, consider restructuring your cluster. Group the ring and a boolean into a cluster, then drop 7 of those into the selector cluster. Then you can use "cluster to array" and "array to cluster" since all elements in the outer cluster will be of the same type.
Also, be careful using rings as type definitions. You probably want to use an enumeration instead. The items in a ring do not update when you update the type definition because they're considered to be cosmetic; the items in an enumeration type definition do update, because the items in an enumeration are considered part of the data type.
Oh my goodness!!
What was MUCH easier than I was trying to make it!!
I was attempting to do this reset, in an incremental fashion, as that later, I'm going to need to change values in this cluster by individual elements....and was using this as a way to try to understand how to iterate between cluster elements, and change the values of each one.
This solution works much better for this 'reset' all solution.
One question on this....with regard to the enum vs the ring menu.
I was actually going to go with the enum, however, I could not find a way to make it LOOK like the ring menu...with the arrow to the side that a user would know to click to present the menu list of choices.
I see with the enum, that you can remove the increment/decrement indicator.....and if the user clicks the control, it will indeed pop up a menu of choices...but there is no 'arrow' on that control to indicate to the user that it is a menu choice there.....
Is there a way to make and enum look like a ring with the "drop down menu" control look?
Again, thank you !!
This helps!
C

Inaccessible with local variable(non-final) via method local inner class

Hi All,
Usually local variables, including automatic final variable live on the stack and objects & instanace variables live on the heap.The contracts for using the method local inner class should allow merely method final variable, not non-final stack variable.
Can anyone please clarify me ,behind the scene what is actual fact why method inner class should not access the stack(method) variable and only allow final variable?
Is anything correlated with the stack and heap aspects?
Thanks,
Stalin.G

[email protected] wrote:
...behind the scene what is actual fact why method inner class should not access the stack(method) variable and only allow final variable?...explained by dcminter and Jardium in [an older thread|http://forums.sun.com/thread.jspa?messageID=10694240#10694240|http://forums.sun.com/thread.jspa?messageID=10694240#10694240]:
...Final variables are copied into inner classes - that's why they have to be declared final; to avoid the developer making an incorrect assumption that the local variable can be modified and have the change reflected in the copy.
When a local class uses a local variable, it doesn't actually use the variable. Instead, it takes a copy of the value which is contained in the variable at the moment the class is instantiated. It's like passing the variable to a constructor of the class, except that you do not actually declare any such constructor in your code.
To avoid messy execution flows to be present in a Java method, the Java language authors thought it was better to allow a single value to be present in such a variable throughout all its life. Thus, the variable has to be declared final.
...HTH

Issue with local variable in forms personalization

Hi All,
I did the following things at last it is give me syntax error, please help me on this.
Rules section:
seq Description Level Enabled
1 Populate Number Function y
Conditions:
T.E : When new item instance
T.O : REQ_LINES.REQUISIOTN_NUMBER
Condition::REQ_LINES.BLANKET_PO_NUM_DSP IS NOT NULL AND
:REQ_LINES.SELECT_LINE='Y'
Processing mode: Not in enter query mode
Actions:
seq: Type: Desc: Langauge: Enabled
1: property: local variable :Y
Object Type: Local Varibale
Target Object: XXNUM
property : Value
Text: = TO_CHAR(${item.req_lines.blanket_po_num_dsp.value})
Rules section:
seq Description Level Enabled
1 Default Number Function y
Conditions:
T.E : When block instance
T.O : New_DOCUMENT
Condition:
Processing mode: Not in enter query mode
Actions:
seq: Type: Desc: Langauge: Enabled
1: property: use of local variable :Y
Object Type:ITEM
Target Object:NEW_DOCUMENT.DOCUMENT_NUMBER
property : Value
*Text: = SELECT TO_CHAR (${var.XXNUM.value}) from dual*
The line which i bold shows me an syntax error, please check the syntax and if it is wrong please correct it.
Thanks and Regards
Zaheer
Edited by: zaheer on Feb 10, 2010 11:25 PM
Edited by: zaheer on Feb 10, 2010 11:25 PM

Hi Zaheer,
Try using this:
Actions:
seq: Type: Desc: Langauge: Enabled
1: property: use of local variable :Y
Object Type:ITEM
Target Object:NEW_DOCUMENT.DOCUMENT_NUMBER
property : Value
Text: = ${var.XXNUM.value}
PS: You might get a message while validating, but you can ignore that.
Regards,
Sujoy

Run a loop when there is any change in value of any control or local variable in side the loop

I am trying to write a program for a complicated multivariate system. I have many different controls connected to different functionality of the system. What I want to do is, run a continuous time loop, but I don't want the program to go over all the different controls and execute all the different functions. Instead can I do the job in a way, that the program will only execute the part that has changes in its control compared to its last loop and not go over the rest of the program in the loop? Hope I make my problem clear!

Have a look at my idea here. The code shown on the left can be done with current tools.
LabVIEW Champion . Do more with less code and in less time .

Re: A problem with local variables, need help.

I don't actually get any error with the code when
compiling,I know. You get it when running. The error is that it doesn't behave like you want. What I was looking for was "at such and such line, I expected this variable to have this value, but it was actually this other value."
Your explanation did clear it up though.

http://java.sun.com/docs/books/tutorial/java/javaOO/variables.html

How can you create a local variable from a boolean control?

I want to create a local variable from a boolean control, but it says that boolean latch actions are incompatible with local variables, but I need a way to check this boolean control in two differents loops, how can I do it?

"Graci" schrieb im Newsbeitrag
news:[email protected]..
> I want to create a local variable from a boolean control, but it says
> that boolean latch actions are incompatible with local variables, but
> I need a way to check this boolean control in two differents loops,
> how can I do it?
Use global variables.
Compare them with a constant Boolean like F or T.
The result is true or false and then you can use it in a Cae-Loop.
Martin

How come my local variable is not updating it's value with respect to what's happening in the while loop?

Hello,
I am trying to extract data out of a while loop as my declarations update with respect to the iteration number. I have attempted to use both local variables and shift registers, but with no luck.
I have also done the following example: http://www.ni.com/white-paper/7585/en and it works like a charm.
I attached the PNG file with local variable declaration circled in red. Will attach a VI in the next respnose.
Thanks
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Attachments:
Local Variable.png ‏366 KB

OK, looking at the code...
Can you explain what it is supposed to do? What's the purpose of the value property node read which only seems to update an indicator.
The inner while loop should proably be a FOR loop, because the number of iterations is known before the loop starts.
Your use of formula nodes seems overly complicated.
LabVIEW Champion . Do more with less code and in less time .

To compare control name with a variable

Hi all
I want to compare the name of a control with a variable inside a loop. Is there any function for it in Labview? Please let me know if it is.
Thanks in advance
Solved!
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Hi ghighuphu,
I am attaching an example VI for our objective.
In the VI we are giving 5 'Variable names', 5 'Variable values' as inputs. And also we are giving an array consisting of the 3 required 'control names'(These 3 controls are on the right side of block diagram). First we are getting only the 3 required values from available 5 values. Now we want to pass these 3 values to their corresponding controls named a,b and c on the right side of the block diagram. So that they can be added and give the output.
I want a generalised solution so that it works for varying number of controls.
Attachments:
Linking1.vi ‏11 KB

Local variable's VariableElement not accessible through treepath

Hi,
I'm extending TreePathScanner visitor to localize and handle certain annotations associated with variables of any kind (field, parameters and local variables).
To do so I overrode the visitVariable method that, as far I understand, should be able to obtain the corresponding javax.lang.model's VariableElement for any variable (whatever its kind) based on the current three path, see code bellow.
It does work well with fields and parameter, however with local variables Trees.getElement simply returns a null. All the information is in fact in the code tree VariableTree node and I could retrieve what I needed from it but rather refrain from using com.sun. ... API if not really necessary and of course implement the processing twice.
Perhaps the javax.lang.model.... object tree is not built for elements within a method body? or is this a bug? com.sun.source.util.Trees#getElement javadoc only says that a null is returned if the element is not "available".
Thanks in advance.
import javax.lang.model.element.VariableElement;
import com.sun.source.util.TreePathScanner;
import com.sun.source.util.Trees;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreePath;
public class MyVisitor extends TreePathScanner<Object,Trees> {
     @Override
     public Object visitVariable(VariableTree node, Trees trees) {
          TreePath path = getCurrentPath();
          VariableElement ve = (VariableElement) trees.getElement(path);
          if (ve != null) {
                        // The case for parameters and fields.
                        process(ve);
          else { // Funnily getElement return null for local variables
                        process(node);
          return super.visitVariable(node, trees);
}

I had a similar problem where trees.getElement(TreePath) was returning null. In my case it had to do with the fact that symbol resolution wasn't done yet. I was trying to invoke my TreePathScanner after calling javacTask.parse() but I had to switch to after calling javacTask.analyze() otherwise trees.getElement(TreePath) always returned null. My issues was with a TreePath for a method though.

Labview FPGA: Why not have local variable without indicator?

In Labview FPGA, to transfer data among parallel loops, there are three ways or maybe more, local variable, global variable and block memory. The problem with local variable is that it needs an indicator along with, not like global variable. I was thinking why Labview doesn't make a kind of local variable not need indicator? I guess local variable itself doesn't cost resource much compared to global variable, however when it comes into indicator, it will cost more. Just an idea, though. I guess there is a reason NI doesn't do that.

As in Labview document, global variable can be used for transfer data among VIs, which local variable isn't capable of.
Global variable is not always a better solution. From my experience, it is still unclear among different compilations using local vs global in terms of resources. A thread here http://forums.ni.com/t5/LabVIEW/FPGA-global-variables-vs-front-panel-items/td-p/1407282 talks about that too.
Stephen, is there any documents say that global makes timing worse? I didn't see this noticeable.

In script logic something like local variable

Hi.
How can I replace CATEGORY.#PLAN with local variable to make impossible saving values of CATEGORY.#PLAN into cube in the code below:
[CATEGORY].[#PLAN] = [CATEGORY].[FACT] * 2
[CATEGORY].[#FORECAST] = [CATEGORY].[#PLAN] * 10

Hi,
You can try using something like:
*WHEN CATEGORY
*IS FACT
*REC(FACTOR = 20, CATEGORY = FORECAST)
*ENDWHEN
Hope this helps.

How to use local variables to pass an image mask correctly

I'm kind of new to labview but i'll try to explain the problem as best as i can: I'm trying to pass an image mask (basically an image) to the next iteration of a while loop using local variables. I think the image passes through the loop with the local variable but i can't read from it correctly for some reason. And I don't think the problem has to do with local variables because i've tried using shift registers and that didnt work either. I think the problem is that you need to do something to read the image correctly again, like using IMAQ copy or something (that didnt work tho), but i can't figure out what the problem is. Does anyone know what the problem is? I know this isnt a great explanation and if its too confusing i could send some snapshots of the program or something. Any help would be greatly appreciated though.
Thanks,
Will

So i attached 2 snapshots of the program to give a better idea of the problem. The first snapshot shows an image getting written to the local variable SavedMask. The second snapshot, which is run on the next iteration of a while loop, shows the local variable SavedMask being read to other image operations. When i run the program, the SavedMask image is always displayed correctly on the front panel, but i can't read from it for whatever reason. I think the problem could be like you said, that im only passing an imaq reference, and i think theres a certain way to extract the image data. Do you know the correct way to extract the image data or how to pass the image data and not just a reference to the data.
Attachments:
first.jpg ‏81 KB
second.jpg ‏68 KB

Reading digital line and local variable

I am using digital lines in my program to start and stop "Flat Sequence Structures"
like time measurement ( 4 sequence, start and stop time with "Tick Count" )
Is it good behaviour if i use once "Read from Digital Line.vi" and other starts and stops etc. with Local variables?
Or can i just use "Read from Digital Line.vi" many times in my VI? (same line)

Most experienced LV programmers try to avoid both sequence structures and local (and global) variables. The state machine architecture is often preferred. Look at the examples with LV and search for "State machine" on this site.
I would probably use one read line or read port VI in a loop and pass the data to other, independent loops for processing (the timing) via queues.
Lynn

How can I Change data in a type def control containing a Xcontrol with a local variable

Hello
I made a Xcontrol and I inserted this control in a type def.
When I want to change the control's data with a local variable in a VI, the VI change nothing. The change of data isn't perform
How can I correct this issue?
Thanks for your help
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Hello,
What's your LabVIEW version ? Do you have a simple example program which demonstrates this behavior ?
I found another discussions related to your issues with Xcontrols:
updating type defs in Xcontrol Facade
No Data Change event generated for a XControl in a Type Def
XControl facede.vi
Hope this helps.
Regards,
Steve M.
National Instruments France
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Simulation & Control with local variables

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