Functional global variables with polymorphic VI

Similar Questions

• Functional Global Variables: an indicator can be used instead of a shift register?

  It is a simple question, but I can't find an answer to it. The model agreed to a functional Global Variable is to use an uninitialized as in this example shift register:

  

  ('Référence IN' and ' Reference to "is actually a pile of references.) There is also a "Se Refnum" case, which comes the straight through the tunnels shift register.

  My question is, why can't we do store the indicator data? It is much simpler to use a shift register (IMHO a non obvious way to store global data!):

  

  The case "Se Refnum" does absolutely nothing. Other functions such as erasure of data can be implemented just as easily. The advantage of the FGV to help avoid race conditions is maintained because you always use the VI to access the data.

  JonP says:

  
  

  Not so much, the Inidicator can happily live outside the case structure, together and Clear would be just assign different values.

  If you have only a case structure, the indicator could not live outside of it.  In order to maintain the indicator data, your design requires that it is not written in for a case of Get.  If you have an exterior structure deal that decides on 'Get' or 'set or clear' and (in the case of "Set or clear") contains the terminal of the indicator and a classiquee case that decides on 'Set' or 'clear '.  However, I would consider this a design below using the standard template of the FGV.

  The difficulty with retrieving the value if you want to do a read operation / writing change. But LV provides many ways to retrieve data from an indicator (one you don't mention is the 'Value' property), do you mean that's all "incorrect"?

  Yes (I mean that they are all incorrect).

  You could hack your way around the design to work with a single structure of matter and the terminal of the indicator being outside using a method to read the value of the indicator and through a tunnel to the structure of the case through wiring for the tunnel of writing indicator in the case of 'Get '.  However, who will require a local Variable or value of property node.  As I said, these (I only mentioned the local Variable originally) are not good choices for performance and scalability.  If you are not aware of the functional differences between the terminals, local Variables and nodes of property value, refer to this article (obviously advantages/disadvantages such as redraw objects on the front panel are not relevant here).

  I guess you could say that indicators should only be written, but it is difficult to be pure!

  No, it's not, just use the classic design of the FGV!

• Functional global variable pending

  Hi all

  I understand, by threads of reading on the forum, that a call to a functional Global Variable will block its execution if the FGV is already consulted one another VI, correct? Is there another way that it would block, apart from those shown?

  The reason for the question is that I have a (non-reentrant) FGV which is read by 8 subVIs simultaneously (they are, in fact, the same vi, but configured for returning) and whose time strangely, access varies based on the number of the subvis running.

  In less than 5 screws are trying to access the FGV, execution is blocked (I guess, because when the FGV is disabled and replaced by a constant there is no problem with running) and access lasts less than 50ms. If this number is between 5 and 8, execution is carried out much faster. My first assumption was that FGV has not been initiated until we call the fifth sub - VI, but I don't know how to check that.

  I can understand that there is something wrong with the FGV, but can't put my finger on. Any ideas?

  Thanks in advance for any help.

  
  

• Functional Global Variable reference

  Hi all

  I want to update the value of the indicator element in primary VI, I don't want to use the global variable, due to the problem of race condition. So I create a functional global variable to control reference. It is reliable and can avoid the race condition critical?

  I have attached two Test VI.

  Thanks for your advice.

  Personally, I use user events to send data to the main VI and then he can update the indicator.  This generally works very well since most GUI screws using a Structure of the event anyway.

• Impossible to go from baseline of connection via functional Global Variable

  Hello

  I'm working on a project of producer/consumer based, which some parties have access to a MySQL database. After the connection to the database, I want to store the reference to the connection inside of a functional global variable. Then other parts of the project that need to use it can only read in the functional global variable.

  For some reason, the reference of the connection is not valid once it has been read functional global variable. It works fine if I have the reference directly from the connection to the request for enforcement VI wiring.

  I have attached a few screws that show the problem, but you will not be able to run them unless you have a database to connect to and hack you the query a little so he selects in your tables.

  SQL_whole_thing works very well. It connects to the database, returns information he requested by the query, and then disconnects. No problem.

  But if I run DB_Connect.vi (which stores the reference to 'DatabaseID_FGV' FGV), follow-up of SQL_Query.vi (which reads to the FGV reference), then I get an error saying that the reference is not valid.

  Anyone has an idea why this happens?

  Thank you

  Christian.

  PS: You'll need DBID_FGVActions.ctl and database_connectioninfo.ctl, also attached

  Your referance on the SR's "outdated" when implementing this way.  Essentially, this means that data in memory to this referance has changed because the referance was stored.  Just because you have changed the data at this location.  This prevents you from spend a refeance for the "old data" and crashing the calling application since the referance Rassi contains assumptions that are more adequate data.

  Consider upgrading this FGV powered Action.  This would be encapulate all the Actions you want to do to the database (connect, disconnect, fecth, writing etc.) and maintain the current referance on the AEs shift register.  Ben establishes a great deal for just this type of functional encapsulation in his famous nugget.  A must read for every programmer

• How to declare global variables with the help of another global variable in ODI

  I declare a variable gloabal using another global variable.
  Suppose for example that:
  
  I have a global variable empid.
  I'm decalaring an another global variable empname refreshing the global variables tab and select statement is
  
  Select empname emp where empno = #GLOBAL .empid - if I write like this I get the error message like character not valid.
  
  Select empname emp where empno = ' #GLOBAL.empid '-if I write like this I get the error message in the number not valid.
  
  I kept the datatype as digital and non-persistent action
  
  Help, please
  
  Thank you in advance.

  Hello

  You must perform this operation from a package.

  V1 (COOLING MODE) - OK---> V2 (REFRESH MODE)

  Thank you
  Fati

• Can I have a single function and variable with createjs names when publsihing of Flash?

  Hey everybody!

  I recently started to use the Toolbox for exporting CreateJS to turn the little button icon animations, done in Flash, content for HTML5. I created 3 files of ".fla" separate icon that animate when spilled.

  With that tag added in my html5 document example, animation works very well:

  < canvas id = "about_btn" width = "85" height = "70" style = "background-color: #FFF" > < / canvas >

  However, once I added several canvas tags, only one icon would be on screen:

  < canvas id = "about_btn" width = "85" height = "70" style = "background-color: #FFF" > < / canvas >

  < canvas id = "news_btn" width = "85" height = "70" style = "background-color: #FFF" > < / canvas >

  < canvas id = "contact_btn" width = "85" height = "70" style = "background-color: #FFF" > < / canvas >

  I discovered that the JavaScript files generated with each 'FLA' file were opposed because they were all using the same variable and function names (Stadium of the exodus, canvas, init(), etc.). Is it possible for me to publish the JavaScript of Flash code with variable and function names specific document? (e.g. about_stage, about_canvas, about_init())

  A work around methood I currently using puts each < canvas > tag in its own iFrame.

  Thanks again for the help!

  -DJ

  Asset JS libraries shouldn't conflict between them, unless there are symbols with the same name. Even in this case, you can change the names of symbols for each FLA avoid collisions.

  Looks like you are trying to copy and paste the code on the HTML preview. It is not really designed for it, and this will lead to collisions of names. You want to rewrite this logic in your own HTML code (code overview using as reference), or rename the variables as appropriate, after you copy and paste.

  Best,

  Concession.

• Functional global variable home (RFGV) is cut off by the controls on the front panel

  Hello

  I though that I had found the ultimate way to dynamically manage memory in a system of Exchange. I read on RFGV here: http://labviewwiki.org/Functional_global_variable and put together a static FGV normal to follow the references for each created instance of memory which I then could easily remember just by name. But now I found that all the RFGV completely stops whenever a front panel with a menu control is used, i.e. 'enum', 'ring' or 'control path. I tried to put in different delivery systems, but not luck. I read about that guy who could have fallen into the same problem: http://forums.ni.com/t5/LabVIEW/Do-I-need-to-use-a-semaphore-when-reading-writing-a-functional/m-p/1... but he got no help what I could see.

  I have not tried semaphores. Don't know what that is. Check my little test code and tell me what I am doing wrong. Or maybe there is no solution in this case I have to abandon the idea of the use of RFGV for anything. Maybe memory held all the VI will be assigned statically.

  Run the code (in LV2009) and watch the 6 LEDS Flash. Then click on anyone of 'enum', 'ring' or 'path' (the file dialog box) and watch off LED when dynamic memory is used to write or read while the continoues to static VI.

  Any suggestions?

  Best regards

  Kai

  If the memories are good, what you're running against is not the user interface thread, but an internal mechanism of LV called the loop of the root, which must run in some things. Specifically, in your case, the method run a VI and showing a menu (a menu real, or a context menu of a ring).

  You can work around this problem (and greatly simplify your code) If you use the call node of the reference instead of the method to execute a VI, but I wouldn't recommend it anyway, since I assume that your code is not what you think it does. In LV memory management can be quite complex if you want to be able to control it, so if you feel you really need, I suggest to start by searching for existing materials on the management of memory in LV

• global variable functional to read and write data from and to the parallel loops

  Hello!

  Here is the following situation: I have 3 parallel while loops. I have the fire at the same time. The first loop reads the data from GPIB instruments. Second readers PID powered analog output card (software waveform static timed, cc. Update 3 seconds interval) with DAQmx features. The third argument stores the data in the case of certain conditions to the PDM file.

  I create a functional global variable (FGV) with write and read options containing the measured data (30 double CC in cluster). So when I get a new reading of the GPIB loop, I put the new values in the FGV.

  In parallel loops, I read the FGV when necessary. I know that, I just create a race condition, because when one of the loops reads or writes data in the FGV, no other loops can access, while they hold their race until the loop of winner completed his reading or writing on it.

  In my case, it is not a problem of losing data measured, and also a few short drapes in some loops are okey. (data measured, including the temperature values, used in the loop of PID and the loop to save file, the system also has constants for a significant period, is not a problem if the PID loop reads sometimes on values previous to the FGV in case if he won the race)

  What is a "barbarian way" to make such a code? (later, I want to give a good GUI to my code, so probably I would have to use some sort of event management,...)

  If you recommend something more elegant, please give me some links where I can learn more.

  I started to read and learn to try to expand my little knowledge in LabView, but to me, it seems I can find examples really pro and documents (http://expressionflow.com/2007/10/01/labview-queued-state-machine-architecture/ , http://forums.ni.com/t5/LabVIEW/Community-Nugget-2009-03-13-An-Event-based-messageing-framework/m-p/... ) and really simple, but not in the "middle range". This forum and other sources of NEITHER are really good, but I want to swim in a huge "info-ocean", without guidance...

  I'm after course 1 Core and Core 2, do you know that some free educational material that is based on these? (to say something 'intermediary'...)

  Thank you very much!

  I would use queues instead of a FGV in this particular case.

  A driving force that would provide a signal saying that the data is ready, you can change your FGV readme...  And maybe have an array of clusters to hold values more waiting to be read, etc...  Things get complicated...

  A queue however will do nicely.  You may have an understanding of producer/consumer.  You will need to do maybe not this 3rd loop.  If install you a state machine, which has (among other States): wait for the data (that is where the queue is read), writing to a file, disk PID.

  Your state of inactivity would be the "waiting for data".

  The PID is dependent on the data?  Otherwise it must operate its own, and Yes, you may have a loop for it.  Should run at a different rate from the loop reading data, you may have a different queue or other means for transmitting data to this loop.

  Another tip would be to define the State of PID as the default state and check for new data at regular intervals, thus reducing to 2 loops (producer / consumer).  The new data would be shared on the wires using a shift register.

  There are many tricks.  However, I would not recommend using a basic FGV as your solution.  An Action Engine, would be okay if it includes a mechanism to flag what data has been read (ie index, etc) or once the data has been read, it is deleted from the AE. 
  
  
  There are many ways to implement a solution, you just have to pick the right one that will avoid loosing data.
  

• How to create a Global Variable through the Project Explorer

  Hello world!

  I know how to create a global variable (in a vi through the range of functions...).

  but I'm missing a way to create one via the Project Explorer.

  It's a missing feature or just this documentation (and the intuition of myself) are missing?

  It would be very convenient.

  THX for your time and hope that answers.

  jwscs

  Right click on my computer > new > new... > select Global Variable.

  EDIT: although I agree with Gerd (he probably wondering why you need so we can recommend a better way ), I rarely use them in easy to write once - read many applications such as security levels overall program at initialization (VER) to read later, but NOT modified.  I know it would be better to make a good class, functional Global Variable (FGV) or a motor Action (AE) but globals ARE practical and safe IF used wisely.

• Why LabVIEW example projects using Global Variables?

  I'm puzzled.  I've been pretty good programmers LabVIEW talks (including some who work for the OR) and came away with the impression that Global Variables should, as a general rule, be avoided, with functional Global Variables (alias VI Globals) generally preferred for "local memory".

  I have studied some of the example distributed with LabVIEW, 2012 and 2013, in particular the proposed acquisition in real time and am struck by the use of Global Variables, where I'd be inclined to use instead a FGV.  For examples, to stop all the loops on the RT target, the overall "All the RT loop Stop" is defined; 'Constants' of configuration (such as timeouts, Streme network names, the names of the journal folder) are kept as Globals; Streme network endpoints are stored in Globals.

  [Note - there is a weird spelling of the second word of the network Streme, above - when I tried to post with the correct spelling, I got an error message saying this word is 'not allowed in this community".]  I apologize for the offense, but I must confess that I do not understand what the problem with the help of the spelling of this word...]

  Why use Globals in these cases, rather than write a bunch of VIGs to hold these data?  Note that almost all these Globals are 'Read' essentially (written once when a resource is acquired, for example) or "Read Only" (treated as if they were a constant).  Indeed, read-only variables can be written as a Subvi with only an output terminal, acting as a (visible, due to the icon) constant.

  I can see advantages to this approach.  On the one hand, VIGs can have error bounds who run the data flow (I just spotted a bug "data flow" in code, I am developing that is based on this model, to read configuration data to an XML file in a world and in the same VI, Global wiring to a "use - me" terminal, but with no guarantee that I'll read the overall after I write it).

  It is, I suppose, a matter of 'speed' - perhaps Global Variables are 'faster' than VIGs (especially if the VIG 'sits' on an error line).  My thought, however, is that this difference is likely to be trivial, especially as these VIGs (or Globals) tend to become "occasional" calls (with the exception of the indicator 'all the loop Stop' which is called once per line).

  Are there other arguments or considerations that make a Variable global to a better choice than a VIG?  Is there a reason that LabVIEW developers put in these start-up of projects LabVIEW?

  BS

  I have to ask, how do you use functional Global Variables?  Like just a Get and Set?  If so, you can use a global variable.

  Yes, globals are faster and use much less overhead.  At the summits of CLA in recent years, we talked about using globals.  The most common use is for Write-Once-Read Many and writing-never-Read Many with configuration data.  It's a good idea to use globals with the constants that can change on you.  It turns out that the world will have the same performance as a constant in this case.  This is done so that you don't have 1 place to edit the 'constant '.

  The rule on "Globals are evil" actually goes back several years when NEITHER had the huge "people of the country are bad" vendata.  But NEITHER explains well how to do things properly.  So I found people, instead of using local variables, using the value property node.  It's even worse because the property causes thread swaps and kills your performance.  It wasn't until I shouted to people to use wires and shift registers I have seen improvements in the way in which people wrote their code.  So people are always riffling in the use of globals and decided to use FGVs with the EEG and fixed rather cases.  But this does not solve the problem of the conditions of race with critical data and you cause an additional burden.

  So from my experience, I use globals all the time for configuration data.  Yes, you must be careful about the race conditions.  But as long as you understand that it is a common and useful practice.

  I would not use a global variable for data that are constantly changing (use registers to offset or Action motor) and/or processes that have critical sections of code (use a motor of Action).

  NOTE: I use the definition of Mercer to FGV (a Get/Set only) and motor Action (many cases which specifically affect the data).

• Global variables or shared unique process variables?

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  Given that the
  introduction of shared variables, whenever I needed a global variable, I have
  use shared unique process variables. But I started now return to
  using the old global variable because I think that there are some significant drawbacks
  to the single shared variable. Here is the ability to search for
  case of variables and also the ability to view or change the value of
  the variable (OK, we have the variable Manager, but I found slow and)
  unstable). My question is, are there reasons to use the new single
  process variable actions on old global variables?

  Dear Terje,

  As you use only the variables on a single system. There is no advantage to the use of unique process shared on Globals variables.

  Infact a global variable uses a little less processing power that a global variable as the implementation of a shared variable single-pocess effect is a global variable with the timestamp feature.
  If you use a shared variable single process, if you don't need the timestamp feature, then disable it to use less processing power.

• How can Global variables can be shared in Subvi?

  I have a question about global variables. not found an answer in the Forum.

  I want to share a few global variables in the different Subvi: starting Subvi first hand.

  define variables, then in second vi, use these variables.

  In my test, if I run LabVIEW, everything is ok. If building an exe, the first sub - VI

  cannot be exited. If the output, the value of global variabels is deleted.  I don't know why?

  Can I use like this? Please help me.

  Thank you.

  attached is my main application. For the release of sub - VI, just call FP. Close.

  The way I underrstand problem:

  There is a main VI (main.vi) that will successively two different screws through a VI reference.

  Let's call them A.i and B.vi. The two access to the same global variable.

  The main VI does not have the global variable.

  At first is short, then closes. B later runs and is expected to access the global variable with the data left by an earlier. I haven't explored it, but I guess that once A ends, the global variable also leaves in memory, forgetting everything

  My suggestion is to place an instance of the global variable in the main VI, forcing them to remain in memory as long as the main VI is running. Apparenlty, this action solved the problem.

  mmm2006 wrote:

  Can I update a global variable in main vi? There are a lot of adjustment, and I don't want to display them.

  I guess it will be sufficient to place the global variable in the main VI to keep in memory. There is no need to read or view its content. Another solution might be to specify the global variable as 'start VI "? I have not tried.

  These are just speculation, because I almost never use globals so my experience is limited. I probably would have A.i write the data to a file B.vi later access, for example.

• How to use use the name of the database schema in global variables?

  I created a global variable with the following query:
  
  "SELECT WeekID from * dr_errdb*.last_dailyload.
  
  
  But when it goes into production and the CONTEXT is changed, certainly will not work because the database is set in the query ("dr_errdb").
  
  What method and how the database directly from the SCHEMA to complete this query?
  
  How to do something like this:
  
  Select WeekID from 'a method '. last_dailyload

  Hello

  rather than hardcode the name of schema, use the API< %="odiRef.getSchemaName" (« nom_logique","d")="" %="" >="" où="" le="" nom="" logique="" est="" le="" nom="" de="" votre="" schéma="" logique="" que="" vous="" avez="" définie="" dans="" la="" topologie="" et="" (j’espère)="" utilisez="" dans="" votre="" « schema »="" pendant="" l’actualisation="" de="" la="">

  Therefore, you can change the physical schema as defined in the context that you use for the logic diagram to point to the different DB.

  Your query is transformed in "SELECT WeekID from < %="odiRef.getSchemaName" (« nom_logique »,="" « d")%=""> .last_dailyload.

  See you soon

  BOS

  Published by: Bos on February 14, 2011 16:16

• How to change a global variable in a function?

  Hello

  I want to change a globalvariable in a function, as a first step I made in this way:

  class Global_output_class
  
  GlobalDim("Correlation_Status,fail_part,End_Exp")
  dim pouet
  
  Correlation_Status = 12
  Call Correlation()
  pouet = Correlation_Status
  
  Function Correlation()
    Dim Global_output_class_sub
    Set Global_output_class_sub = new Global_output_class
  
    Correlation_Status = 1
    fail_part = 2
    End_Exp = 3
  
    Global_output_class_sub.CorrelationStatus = Correlation_Status
    Global_output_class_sub.failpart = fail_part
    Global_output_class_sub.EndExp = End_Exp
    set Correlation = Global_output_class_sub
  End function
  

  In this case: correlation_status receives a value of 12, then I go to my correlationn() function where it became 1

  Then he comes out of the Sub-function and takes the previous value of the program (12) (I hate that)

  To solve the problem I did it this way:

  class Global_output_class
  public CorrelationStatus
  public failpart
  public EndExp
  end class 
  
  GlobalDim("Correlation_Status,fail_part,End_Exp")
  
  Correlation_Status = 12
  Set Global_Output = Correlation()
  Correlation_Status = Global_Output.CorrelationStatus
  fail_part = Global_Output.failpart
  End_Exp = Global_Output.EndExp
  pouet = Correlation_Status
  
  Function Correlation()
    Dim Global_output_class_sub
    Set Global_output_class_sub = new Global_output_class
  
    Correlation_Status = 1
    fail_part = 2
    End_Exp = 3
  
    Global_output_class_sub.CorrelationStatus = Correlation_Status
    Global_output_class_sub.failpart = fail_part
    Global_output_class_sub.EndExp = End_Exp
    set Correlation = Global_output_class_sub
  End function
  

  This way my global value are copied in themselves after leaving the subprogramme

  I had a lot of variables, is there an easier way for the global variable in a function of change keep the value after you leave the service?

  Thanks for the help,

  Fred

  Hi Fred,.

  It is possible to use a global variable defined, but the best way is to use a function call (or procedure call) with parameters. Please first find the right solution for a function call with parameter and the suboptimal way with a comprehensive valiable:

  dim oParameter
  set oParameter = new cGlobal_output_class
  
  oParameter.Correlation_Status = 12
  
  msgbox "Correlation_Status before Call Correlation: " & oParameter.Correlation_Status
  Call Correlation(oParameter)
  msgbox "Correlation_Status after Call Correlation: " & oParameter.Correlation_Status
  
  '-------------------------------------------------------------------------------
  Function Correlation(oPara)
    msgbox "Correlation_Status in the FUNCTION before change: " & oPara.Correlation_Status
    oPara.Correlation_Status = 1
    oPara.fail_part = 2
    oPara.End_Exp = 3
    msgbox "Correlation_Status in the FUNCTION after change: " & oPara.Correlation_Status
  End function
  
  '-------------------------------------------------------------------------------
  class cGlobal_output_class
    dim Correlation_Status,fail_part,End_Exp
  end class
  

  call GlobalDim("oPouet")
  
  dim oPouet
  set oPouet = new cGlobal_output_class
  
  oPouet.Correlation_Status = 12
  
  msgbox "Correlation_Status before Call Correlation: " & oPouet.Correlation_Status
  Call Correlation()
  msgbox "Correlation_Status before Call Correlation: " & oPouet.Correlation_Status
  
  '-------------------------------------------------------------------------------
  Function Correlation()
    msgbox "Correlation_Status in the FUNCTION before change: " & oPouet.Correlation_Status
    oPouet.Correlation_Status = 1
    oPouet.fail_part = 2
    oPouet.End_Exp = 3
    msgbox "Correlation_Status in the FUNCTION after change: " & oPouet.Correlation_Status
  End function
  
  '-------------------------------------------------------------------------------
  class cGlobal_output_class
    dim Correlation_Status,fail_part,End_Exp
  end class
  

  Greetings

  Walter