Variation between local variables

Hello, I use version 7.1 for developing a scada application for seeing liquid tanks levels, and I need to see the flow depicted at tank indicator from one to another in this way.
The first tank increase it liquid level only when an electrovalve is activated, the level is writen in a numeric indicator.
The liquid flows from a second tank only when a second electrovalve is activate.
When both electrovalves are activated the level variation must be saw both indicator and controls.
I fail in third point, Is it possible to make it as I madeor anything similar? The vi I made became crazy when I turn on.
Thank you very much.
Attachments:
levels.vi ‏46 KB

1. Your VI is designed to only run one time. It runs once. Then it stops. My guess is your are using the Run Continuously button. Don't. It is only intended for special situations like if you want to debug a VI. If you want your VI to keep running, then use a while loop around it and a stop button.
2. You need a wait statement in your loop. Without a wait statment, your VI will run as fast as the CPU allows.
3. Local variables are almost always used incorrectly by new LabVIEW users. Read this thread Why some people say Local Variables are bad... for some reasons why.
Then I would recommend looking at the online LabVIEW tutorials
LabVIEW Introduction Course - Three Hours
LabVIEW Introduction Course - Six Hours

Similar Messages

What is difference between local variable and property node ?

What is difference between local variable and property node ?
" 一天到晚游泳的鱼"
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To make things clear, here are two small examples that show how nasty locals and value properties can be to the naive programmer.
- Open the diagram of the race condition.vi before running it and try to predict what will be the values of the two counters after the third run.
- Use the Compare Locals Properties and Wires.vi to find out how slow locals and value properties can be (times 1000+).
This being demonstrated, I must add that I use globals and value properties quite often, because they are often very convenient
Chilly Charly (aka CC)
E-List Master - Kudos glutton - Press the yellow button on the left...
Attachments:
Race condition.vi ‏9 KB
Compare Locals Properties and Wires.vi ‏18 KB

No difference between using a local variable and a notifier in timed parallel loops?

The example code "Pass Data With Notifiers.vi" that came with LV 7.1 illustrates using notifiers with parallel loops. Just looking at two of the loops, the one that generates the sine wave and the one for "User 1", you can change the timing of the two loops and you can change the condition of the "Ignore Previous" status on the "Wait on Notification". I have a special case of this to consider, where I'm wondering if there's any reason not to use a local variable instead of the notifier:
Set the delay on the generator portion (which contains the Send Notification) to something very short, say 5 ms. Set the delay on the User 1 (which contains the Wait on Notification) to something relatively longer, say 200 ms. Set the Wait on Notification to False. Now you have a situation where the User 1 loop action is contingent only upon the loop delay time, since each time the loop timer runs the loop there will always be a value in the notifier. In this case it seems to behave just like the case where you update a local variable in the fast loop and read it in the slow one.
Is my understanding correct? Would there be a performance difference between the two methods? What do you prefer in this situation and why?
Thanks,
Hosehead

Hi H.,
I think your idea is to write to a Global Variable in the data-producer VI, and read it in the data-consumer VI(?)
One reason this might be less efficient than using Notifiers is if you want to graph every new value in the "consumer" - or make sure the value read in the consumer has changed at least once since the last loop.
> since each time the [consumer] loop timer runs the loop there will always be a value in the notifier...
> Would there be a performance difference between the two methods?
If you don't use the Notification "event" to synchronize the producer and consumer, then to be sure the consumer gets a new vaue, you've made the producer loop faster - every 5 ms - a waste of cpu-cycles. More often the situation is reversed, that is, there's a consumer that needs to see every single new value, and (without events) the consumer must loop faster than the producer (to catch every new value) - this is called polling and it wastes cpu-cycles.
Just about anytime one's tempted to make a loop execute "fast" to check on some value (or to make sure there's a fresh value,) there's an opportunity to improve performance through synchronization with events (including notifiers, queues, occurrances, semaphores, and rendezvous')
tbd
Message Edited by tbd on 07-09-2006 03:51 AM
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)

How to pass local variables between different sequence files?

Actually i want to pass the data (local variable) from my process model file to a client file. The client file only has the callbacks and those callbacks require some parameters as input which is available in local variables of my process model sequence file. I do not want to use Station Globals.
Please tell me any other way by which i can pass that data.

Which Locals do you want from the model. Every sequence has it's own Locals and there are a bunch of sequences in every process model. Do you want the entry point's Locals? A callback's Locals? Just one of the sequence's Locals? Some Models have way more entry points than others. What if your sequence file is ran with a different entry point?
One option is to create your own callback in the model and pass the data to it as parameters. Then add that callback to your client sequence file and get it out of the parameters.
If you simply want the entry point's locals and you are in your Main Sequence then you could use RunState.Caller.Locals.VariableName. This assumes you will use the same entry point every time you run that sequence file. Or assumes that every entry point you run has the same Local variable name.
Maybe there is an API method that exposes what you are looking for. What is your goal?
Regards,
jigg
CTA, CLA
teststandhelp.com
~Will work for kudos and/or BBQ~

Data Acquisition - using local variables to write data to a file

Hello,
I am running a Data Acquisition vi (currently in LabVIEW 7.1 but soon to be updated to 8.2) that collects ~100 parameters of data from several sources contained in a while loop. The current configuration (which I did not write) uses very few subVIs and writes to ~100 local variables to store each parameter. It then reads all the local variables and builds an array of all the strings, converts then to a spreadsheet string, then uses the write characters to file function to append to a datafile. I am trying to clean things up and have came up with subVIs to collect the data from the following sources:
8 serial port sources collecting btwn 8 and 20 parameters each
~15 thermocouple readings
~10 analog inputs
~20 parameters read off an ARINC 429 bus.
I have come up with a subVI to read each of the sources and have placed the subVIs in the while loop. Each subVI outputs the data that it collects in array or cluster form. I was wondering how best to write each parameter to a CSV file at between 1 and 10 Hz. Should I write each subVI output to a LV and then read them off as was done before (the difference being that I have reduced the # of LVs to ~10 vs >100?
I should add that precise timing is not that important, so if all the subVIs are not collecting simultaneously (which I understand that they won't be), it does not really matter.
Thanks.

Hi jilla,
jilla wrote:
What I think that you are saying is to turn the outputs of the 4 subVIs into inputs of a 5th subVI that writes to the data file. Correct?
Yes. It may sound like a fine-point, but I beileve it's better to create a VI specifically for formatting data - in your example, 4 arrays IN, a single string OUT. Then write the string to file as a seperate operation. GUI-displayed data can go through a similar transformation, the four arrays wired to a subVI which builds output-structures specifically for display. It's a beginner's mistake to put lots of individual controls and indicators on the screen when groups of them are naturally related (in an object-oriented sense.) Use clusters to group related controls - this will keep the diagram much cleaner.
One more question: at what point (either # of data points or frequency of data collection) does it become necessary to use queues? Thanks.
Well, there's not really a clearly definable "point". I'd say if your update-rate climbs above 100Hz, or you witness poor program or system performance, then it's time. The scenario you've described is a fairly simple acquire/display&log loop - and simple is good. Then-again people can't see/react-to updates faster than about 10Hz - so it doesn't make sense to sacrifice performance - if performance becomes an issue.
Re: queues: Queues are sometimes used to buffer data that's "produced" in one place and "consumed" in another.
Here, if/when logging data, you're logging with every DAQ. I wouldn't recommend using a queue to transport data from a "DAQ loop" to a "Logging-loop" - those functions can be in the same loop. Should/could a queue be used to get data from a "DAQ loop" to update the GUI at a lower frequency? Sure, but a Notifier might be a better choice. Further, in the (simple?) program you've described, you might use a case structure (True/False) to only update FP indicators every "X" iterations - a simple solution that doesn't require Queues or Notifiers.
Cheers!
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)

Problem using local variable in event loop

I have a state machine from which I want to monitor various controls, including "Start" and "Stop" buttons. Not every state needs to monitor the controls. At present, most states run timed loops. In the first state that reads the front panel, I have an Event structure (inside a While loop) that monitors the various controls' Change Value events. For numeric controls, I update variables (in shift registers) as needed. The "Start" button is used to end the While loop controlling the Event structure, allowing the State to exit to the next state.
My problem comes in subsequent states that employ this same idea. Here, I put a Local Variable bound to the Start button and use the same code, but it frequently happens that when I enter this particular state, I cannot "turn on" the control -- I push the button, but it stays off. Curiously, if it was On when I enter, I can turn it off, but then I'm stuck not being able to turn it on.
I mocked up a very simply routine that illustrates this. There are two sequences (corresponding to the two states). Both use an Event loop with a local variable bound to my Stop button (really this is an LED control with custom colors). I've deliberately moved the "initialization" (the declaration of the control in the block diagram) out of the Event loops -- putting it inside the first loop modifies the behavior in another strange way.
Here's my thinking on how I would expect this to work: The code outside Event Loop 1 should have little effect. Assume the Stop button is initially Off. You will "sit" in Event Loop 1 until you push the Stop button, changing its value to True; this value will be passed out of the Event case and cause the first While loop to exit. You now enter the second sequence. As I understand the Exit tunnel, it defaults to "False", so I'd expect to stay in the second Event loop until I turn the Stop button from On to Off, which will pass out a False, and keep me in the While for one more button push. However, this doesn't happen -- I immediately exit, as though the "True" value of the Stop local variable is being seen and recognized by the Event loop (even though it hasn't changed, at least not in the context of this second loop).
An even more curious thing occurs if I start this routine with the Stop button turned on. Now I start in my Event loop waiting for a change, but this time the change will be from On to Off, which won't cause an exit from the frame. This will be reflected by having the While loop count increment. We should now be in the state of the example above, i.e. in an Event loop waiting for the control to be pushed again, and turned On. However, clicking the control has no effect -- I cannot get it to "turn on".
Where am I going astray in my thinking? What is it about this method of doing things that violates the Labview paradigm? As far as I can tell, what I'm doing is "legal", and I don't see the flaw in my reasoning, above (of course not -- otherwise I'd have fixed it myself!). Note that because I'm using local variables inside Event loops (and I'm doing this because there are two places in my code where I want to do such testing), the Stop control is not latching (as required). Is there something that gets triggered/set when one reads a latched control? Do I need to do this "manually" using my local variable?
I'll try to attach the simple VI that illustrates this behavior.
Bob Schor
Attachments:
Simple Stop Conundrum.vi ‏14 KB

altenbach wrote:
Ravens Fan wrote:
NEVER have multiple event structures that share the same events.
Actually, that's OK. NOT OK is having multiple event structures in the same sequence structure.
See also: http://forums.ni.com/ni/board/message?board.id=170&message.id=278981#M278981
That's interesting. I had always thought I read more messages discouraging such a thing rather than saying it was okay. Your link lead me to another thread with this message. http://forums.ni.com/ni/board/message?board.id=170&message.id=245793#M245793. Now that thread was mainly concentrating on registered user events which would be a different, but related animal.
So if you have 2 event structures they each have their own event queue? So if you have a common event, one structure pulls it off its event queue and it does not affect the other structure's event queue? I guess the inherent problem with this particular VI was that the second event structure locked the front panel. Since the code never got to that 2nd event structure because the first loop never stopped because the change was from true to false. After reading your post and the others, I did some experimentation and turned off the Lock front panel on the 2nd structure, and that prevented the lockup of the program.
Overall, the example VI still shows problems with the architecture and I think your answer should put the original poster on the right track. I think as a rule I would probably never put the same event in multiple structures, I feel there are better ways to communicate the same event between different parts of a program, but I learned something by reading your reply and about how the event structures work in the background. Thanks.

Final attributes and local variables - performance ??

Hi all,
I and a colleague have done some performance testing regarding the use of final attributes and final local variables, e.g.
with final:
public class MyClass {
private final int i;
public final void myMethod() {
    final int j = 5;
    // do something with i and j
}vs. non-final:
public class MyClass {
private int i;
public final void myMethod() {
    int j = 5;
    // do something with i and j
}I couldn't find any speed differences in a small test program, but my colleague did so in his application. Who is right ??
Still, I will have do some formal testing next week and I will post the results.
I'd prefer the version using final anyway because I find it better readable, but the issue I am having is whether I'll spend 2-3 days going through the program making everything final or not.

I made some tests with final arguments to a method: I could not find any difference between final and non-final arguments. code is posted below
import java.io.*;
import java.net.*;
import java.rmi.*;
import java.util.*;
import javax.ejb.*;
import javax.naming.*;
import javax.rmi.PortableRemoteObject;
import junit.framework.*;
import junit.extensions.*;
public final class FinalVariablesTest extends TestCase /* from junit */ {
     * Constructors
    public FinalVariablesTest(String name) {
        super(name);
     * helper methods/classes
    protected void setUp() throws Exception {
        super.setUp();
    protected void tearDown() throws Exception {
        super.tearDown();
     * Test Suite
    public static void main(String[] args) {
     junit.textui.TestRunner.run(suite());
    public static Test suite() {
        return new TestSuite(FinalVariablesTest.class);
     * Test Cases
    /** tests the effect of passing an (final or non-final) int parameter
     to a method which uses the variable in a for loop.
     <p>
     Linux System:
     cat /proc/cpuinfo
     processor       : 0
     vendor_id       : GenuineIntel
     cpu family      : 6
     model           : 8
     model name      : Pentium III (Coppermine)
     stepping        : 1
     cpu MHz         : 501.146
     cache size      : 256 KB
     fdiv_bug        : no
     hlt_bug         : no
     sep_bug         : no
     f00f_bug        : no
     coma_bug        : no
     fpu             : yes
     fpu_exception   : yes
     cpuid level     : 2
     wp              : yes
     flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr xmm
     bogomips        : 999.42
     </pre>
     <p>
     Results:
     <pre>
     java version "1.4.0"
     Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
     Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
     final     non-final
     498     500
     491     494
     491     493
     491     494
     534     494
     492     494
     491     494
     492     493
     491     494
     495     494
     4966     4944 (Totals)
     </pre>
    public final void testIntParametersToForLoop() {
     final int RUNS = 10;
     final int INNER = 1000000;
     final int OUTER = 10;
     System.out.println("-----------------------");
     System.out.println("testIntParametersToForLoop");
     for(int i=0; i<RUNS; i++) {
         outerFinalIntParametersToForLoop(INNER, OUTER);
         outerNonFinalIntParametersToForLoop(INNER, OUTER);
    private final void outerFinalIntParametersToForLoop(final int INNER,
                                   final int OUTER) {
     // with final var in for loop
     long start0 = System.currentTimeMillis();
     for(int i=0; i<OUTER; i++) {
         innerFinalIntParametersToForLoop(INNER * i);
     long end0 = System.currentTimeMillis();
     System.out.println("      final:       " +
                  ( end0 - start0 ) + " milliseconds");
    private final void outerNonFinalIntParametersToForLoop(final int INNER,
                                      final int OUTER) {
     // with non-final var in for loop
     long start1 = System.currentTimeMillis();
     for(int i=0; i<OUTER; i++) {
         innerNonFinalIntParametersToForLoop(INNER * i);
     long end1 = System.currentTimeMillis();
     System.out.println(" non final: " +
                  ( end1 - start1 ) + "       milliseconds");
    private final void innerFinalIntParametersToForLoop(final int INNER) {
     for(int i=0; i<INNER; i++) {
         int testVar = i * INNER;
    private final void innerNonFinalIntParametersToForLoop(int loops) {
     for(int i=0; i<loops; i++) {
         int testVar = i * loops;

While trying to invoke the method java.lang.String.length() of an object loaded from local variable 'payload'

Hi,
Our PI is getting data from WebSphere MQ and pushing to SAP. So our sender CC is JMS and receiver is Proxy. Our PI version is 7.31.
Our connectivity between the MQ is success but getting the following error while trying to read the payload.
Text: TxManagerFilter received an error:
[EXCEPTION]
java.lang.NullPointerException: while trying to invoke the method java.lang.String.length() of an object loaded from local variable 'payload'
       at com.sap.aii.adapter.jms.core.channel.filter.ConvertJmsMessageToBinaryFilter.filter(ConvertJmsMessageToBinaryFilter.java:73)
       at com.sap.aii.adapter.jms.core.channel.filter.MessageFilterContextImpl.callNext(MessageFilterContextImpl.java:204)
       at com.sap.aii.adapter.jms.core.channel.filter.InboundDuplicateCheckFilter.filter(InboundDuplicateCheckFilter.java:348)
       at com.sap.aii.adapter.jms.core.channel.filter.MessageFilterContextImpl.callNext(MessageFilterContextImpl.java:204)
I have searched SDN but couldn't fix it. Please provide your suggestion.
With Regards
Amarnath M

Hi Amarnath,
Where exactly you are getting this error?
If you are getting at JMS Sender communication channel, try to stop and start the JMS communication channel and see the status, also use XPI Inspector to get the exact error log.
for reference follow below blogs:
Michal's PI tips: ActiveMQ - JMS - topics with SAP PI 7.3
Michal's PI tips: XPI inspector - help OSS and yourself
XPI Inspector

How to specify a unique integer for each local variable defined in TestStand?

I have a .net application that reads all TestStand local variables, but for the .net application each local variable should have a unique integer number. Iterating through the locals and storing the index is not a good solution, because if a local variable is moved or deleted, the index will change.
Does anyone know how to do this in TestStand or having an idea how to this in my .net application?
Thanks.

Thanks Doug for your reply. Using a GUID is not an option because this ID is too long. I will try to explain why I need this ID for. I have a lot of C# code that generates code to deal with a lot of instruments. For example to configure a device, user defined variables can be used to specify some settings or to store results. These variables are not stored in the generated code with a name but with an integer number. Now I want to try to be use all our existing device driver code with the TestStand sequencer. So, I need a translation between the name of a TestStand local variable and an integer number. After constructing the interface to my code I want to read all the variables from TestStand and now I need the integer ID to do the mapping to my variables. I know that I can use use your proposition 2 by encoding the unique ID into the name of the variable and parse the name of the variable to get it back, but this is not an automated way. This will be rather difficult if there are several hundreds of variables. For this reason I am looking for an alternative way. Looking forward for your response. Best regards

How to bind local variables in complex query in PL/SQL

Hi
I have long complex query with local varibales; when I run in Dynamic SQL I get an error. Not sure which is the easiest way to bind local variables.
L_QUERY := q'[select m.segment1 col1,
      '1' col2,
      '13' col3,
      l.operand col4,
      0 col5,
       'Y' col8,
      'N' col9,
      'N' col10,
   decode(h.name,'09_UKOR_*','EOS Credit','10_UKOR_*','TopUp','11_UKOR_*','Main') col18
from qp_list_headers_v h,
      qp_list_lines_v l,
      mtl_system_items m
where h.name in ('09_UKOR_*','10_UKOR_*','11_UKOR_*')
and h.list_header_id = l.list_header_id
and m.inventory_item_id = l.product_attr_value
and m.organization_id = 84
UNION all
SELECT qs.PRODUCT_ATTR_VALUE col1,
       hca.account_number col2,
       decode (su.site_use_code,'BILL_TO','21','SHIP_TO','18') col3,
       0 col4,
       qs.operand col5,
       null col6,
       null col7,
       'N' col8,
       'Y' col9,
       'N' col10,
--Local variables
      (case when (trunc(nvl(qq.start_date_active,sysdate)) between l_cur_year_from and l_cur_year_to) and
                  ( trunc(nvl(qq.end_date_active,l_cur_year_to)) >= trunc(l_cur_year_to) ) then    'TopUp'
            when (trunc(qq.start_date_active) between l_next_year_from and l_next_year_to) and
                  ( trunc(nvl(qq.end_date_active,l_next_year_to)) >= l_next_year_to) then   'Main'
            when (trunc(qq.start_date_active) between l_last_year_from and l_last_year_to) and
                  ( trunc(nvl(qq.end_date_active,l_last_year_to)) >= l_last_year_to ) then 'EOS Return'
       end )col18,
--Local variables
       (case   when (trunc(qq.start_date_active) between l_next_year_from and l_next_year_to) and
                  ( trunc(nvl(qq.end_date_active,l_next_year_to)) >= l_cur_year_to ) then   'N'
          else
                'Y' end ) col21
   FROM qp.qp_list_headers_b qlhb,
        qp.qp_list_headers_tl qlht,
        qp.qp_qualifiers qq,
        qp_modifier_summary_v qs,
        hz_cust_site_uses_all su,
        hz_cust_acct_sites_all sa,
        hz_cust_accounts hca
WHERE 1=1
      and qlhb.LIST_TYPE_CODE       = 'DLT'
      and nvl(qlhb.active_flag,'Y') = 'Y'
      and qlhb.list_header_id       = qlht.list_header_id
      AND qq.list_header_id         = qlhb.list_header_id
      and qq.list_type_code         = qlhb.LIST_TYPE_CODE
      and qq.QUALIFIER_CONTEXT      = 'CUSTOMER'
      and qs.list_header_id         = qlhb.list_header_id
      and qs.LIST_LINE_TYPE_CODE    = 'DIS'
      and su.site_use_id            = qq.qualifier_attr_value --1064
      AND su.cust_acct_site_id     = sa.cust_acct_site_id
      AND sa.cust_account_id       = hca.cust_account_id ]';
--call Dynamic SQL function
l_cursor := DBMS_SQL.OPEN_CURSOR;
DBMS_SQL.PARSE(l_cursor, p_QUERY , DBMS_SQL.NATIVE);
l_rows := DBMS_SQL.EXECUTE(l_cursor);
Any help will be much appreciated.
iI guess I should use DBMS_SQL.BIND_VARIABLE to bind all variables seperately so not to mess with query

1) What is the error you get?
2) If you use bind variables inside a query, you should prefix them with colons, so use :l_cur_year_from etc.
3) Why are you using dbms_sql instead of native dynamic sql and/or ref-cursors?
Toon

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
Solved!
Go to Solution.
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

Best way to remove local variables

Hello,
I have been told that I need to remove all the local variables in my VI, because they are slow. I can not seem to find a good option for replacing them but keeping the same functionality.
What I am using the local variables for is to update 3 different graphs on the front panel from 3 different sources. Each of these sources are located in while loops so that data can be acquired asynchronously. In closing these 3 while loops is a case statement. The case statement is for switching between acquiring and saving the data or just acquiring data. The local variables are used to update the indicators and graphs from the acquiring and saving data case. It is these local variables that I need to remove.
Does anyone have any suggestions?
-- Z

Zurvan wrote:
I have been told that I need to remove all the local variables in my VI, because they are slow.
Who told you that?
As others have said, local variables typically don't cause slowdown (They cause additional datacopies in memory, have the potential of causing race conditions and cause messy code).
What is "slow" in your definition? (missing data, cannot keep up with the instrument, slugging UI, etc.).
What is the CPU use when your program runs?
So apparently you have a loop that updates all indicators from local variables. What is the loop rate of that display loop? Do you spin that millions of times per second or pace it at a reasonable rate? How much data is in the graphs?
Remember, a graph does not need to update unless the data changes.
LabVIEW Champion . Do more with less code and in less time .

How to avoid "The local variable ___ is never read" warnings

If you create an instance of a class using something like:
MyClass myClassInstance = new MyClass(param1, param2, ...);
And everything you require this class to do is done from within it's constructor then you always get a warning saying "The local variable myClassInstance is never read" with the class you're making this initialization from.
Is there a good practice technique to avoid these warnings?
On a large project this type of warning can become numerous and it would be cleaner to avoid them.
Thanks

TimThe.., I disagree about the result of a bad design
comment. In simple cases it can be beneficial to
only require an object's constructor, then that
object's actions are self contained and its methods
can then be called from its own constructor. In the
right situations this can help to loosen coupling
between classes and increase encapsulation.I disagree with that. If your code depends on behaviour that is carried out by a constructor, you have a dependency on a concrete class, which is a nice quick way to tightly couple classes. You'd achieve looser coupling if the desired behaviour was inside a method, which was in turn declared on an interface

When debugging package, local variables always listed as 'null'

When I'm debugging a package procedure, if I try to inspect any local variables by hovering the mouse cursor over them, the floating text that appears always says they're set to null - even though I know (because the procedure works as expected) that there must be a value there. Also, local variables don't appear in the 'Data' debug tab; and if I drag the local variables into the 'Watch' tab, their value is listed as null.
Using v1.1.2.25 against a 9.2.0.6 db - anyone have any ideas..?
Cheers,
James

Local variables should be used whenever you need a value only in a single method and don't need to remember it's value between two invocations of that method.
A perfect example would be the counter in a for-loop.

How to call a local variable from another component controller

Dear Experts,
I have created 1 component controller(Controller Name as B)and methods.In that methods I Have declared Local variable(For ex data: Lv_flag). I have Created 1 more component and name as A. I used Component B in Component A(Using component usage). In A component controller I have created methods.Now I want to call a local variable Lv-flag in this method from B controller Method. Please reply your valuable answer.

Karthikeyan,
Please make sure that flag attribute is under some node, say NODEA. NOW please select the interface node property and input element of NODEA.
now NODEA will be available in interface controller. Interface controller acts like a global controller between two different components.
So from interface controller you can take that flag value.
pls reply back if you have any confusion.
Regards
Srinivas

Variation between local variables

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