LabVIEW Idea Exchange

LabVIEW  has a somewhat hidden feature built into the variant attributes functionality that easily allows the implementation of high performance associative arrays. As discussed elsewhere, it is implemented as a red-black tree.

 

I wonder if this functionality could be exposed with a more intuitive set of tools that does not require dummy variants and somewhat obscure VIs hidden deeply in the variant palette (who would ever look there!).

 

Also, the key is currently restricted to strings (Of course we can flatten anything to strings to make a "name" for a more generalized use of all this).

 

I imagine a set of associative array tools:

 

 

• Create associative array (key datatype, element datatype)
• insert key/element pair (replace if key exists)
• lookup key (index key) to get element
• read all keys
• delete key/element
• delete all keys/elements
• dump associative array to disk
• restore associative array from disk
• destroy associative array
• ... (I probably forgot a few more)

 

When programming with large applications, often times you'll have clusters carrying a lot of information.  If you hover over the cluster wire and observe Context Help, you might see something like this:

 

This Context Help window above is rather large and doesn't necessarily make it any easier to see the structure or contents of the cluster. My proposed idea calls for the ability to expand or collapse the cluster contents within the Context Help window, such as this:

 

What do you think?

 

This is written as both an Idea and as a Community Nugget.

 

Did you know there exists a function that decreases code fragility when it comes to typecasting and type converting datatypes? It's called 'Coerce to Type', and I bet you've never heard of this function unless you have kept up with this conversation. Thanks to RandyP for creating that Idea which culminated in a 'public' release of the Coerce to Type function.

 

 

Since that post, I have become aware of potential risks/bugs I had been proliferating in my coding style. First, I will briefly describe my understanding of the difference between typecasting and typeconverting in the context of LabVIEW. Next, I'll show a few use cases where this node increases code robustness. Finally, it's up to you to Kudos this Idea so we get Coerce to Type officially supported and in the palette!

 

Simply, "type converting" preserves the value of a wire, and "typecasting" preserves the raw bits that express that value on a wire. These two concepts are not interchangeable - they perform distinctly different data transfer functions (which is why they show up on two separate subpalettes: "Numeric>>Conversion" and "Numeric>>Data Manipulation"). Then there's this new function: Coerce to Type. I think of it as a Coerce-Cast combo. The data input is first Coerced to the datatype harvested from the top input, and then it is typecasted to that type.

 

Dynamic event registration is sensitive to the name on the wire, and for documentation's sake it has historically been important to typecast the event source ref to achieve a good name. Well, typecasting refs can get you into trouble (ask Ben), especially if you change the source control type while forgetting to update your "pretty name" ref constant.

 

 

My next favorite example is when you need to coerce a numeric datatype into an enum. Sometimes it's impossible to control the source datatype of an integer, while it's desirable to typecast the value into an enum for self-documented syntax inside your app. 

 

For instance, take the "standard" integer datatype in LabVIEW - I32 - and cast it to an enum. You're going to get some unexpected results (assuming, you expected the *value* to be preserved). Consider the following scenario:

 

1. You desire to typecast a plain integer '2' into an enum {Zero, One, Two, Three}, and after 45 minutes of debugging, realize "Typecasting" has hacked off 75% of the bits and clobbered the value. Drats!
2. The enterprising engineer you are, you determine how to fix the problem with a deftly-placed "Coerce to U8". (This is one of the fragile errors I proliferated prior to learning about this node)
3. Maniacal manager/customer comes along and says "I want that enum to count to 10k". Drats again. A datatype change from U8 to U16 for the typedef'd enum, and a lot of typing with the wretched enum editor. Finally, two hours into testing and wondering why the program doesn't work, you realize you also forgot to replace all of the Type Converts to U16 (this is the definition of fragile code: you change one thing, and another thing(s) breaks).
4. Rockstar Programmer Epiphany: use Coerce to Type, bask in your robust code. You even enjoy data value preservation from floating point numbers.

It would help a lot if we have an option called pause on first Error. So that the VI at the node/primitive that generates the error and highlights that node so that user decides to continue or abort.

 

Can the the options on the data type Representation pallette be changed from grey to match the color of the numerical icons and terminals?

 

Thank You!

Melissa McQueen

For distribution, only package necessary libraries in installer packages built with the project. A lightweight UI, server, or client does not need a full 70MB+ installer that bloats out to a few hundred MB's once installed! A colleague has remarked that the total size of our LabVIEW application+RTE EXCEEDS the entire size of the XPe image running on the embedded computer! This becomes an issue when distributing software upgrades to places in the world without high-speed internet connectivity.

It would be helpful to have an array control property that fixed the number of elements in the array control to the specified size.  This would allow the developer to programmatically set the array control dimensions such that the user is unable to add new elements to the array.  This is specifically necessary when the number of elements in the array control may vary and may also be too large to display all of the elements.  If the scrollbar(s) are visible, then the user will always be able to add a new element add the bottom by editing the available empty element value.  This is undesireable if the developer wants to prevent the addition of new elements by the user.

   

Please see the discussion forum post below for the details of the issue and current workaround.

http://forums.ni.com/t5/LabVIEW/initialize-array-control-dimension/m-p/1221930#M520867

 

 

Thanks
Dan

 

The Arduino Due is a 32 bit ARM based microcontroller board that is destined to be very popular. It would be great if we could programme it in LabVIEW. This product could leverage off the already available LabVIEW Embedded for ARM and the LabVIEW Microcontroller SDK.

 

The Arduino Due is currently in developer trials and is due out later this year. It is expected to be about $50 and is open hardware. The ARM chip is an Atmel SAM3X8E ARM Cortex M3 running at 84 MHz resulting in 100 MIPS of performance. By way of comparison, the current LabVIEW Embedded for ARM Tier 1 (out-of-the-box experience) boards have only 60 MIPS of processing power.

 

The Arduino brand has an enormous following and Google has selected the Arduino Due for their recently introduced (28 June 2012) Accessory Development Kit for Android mobile phones and tablets (the ADK2012).

 

(By the way, the currently-available LabVIEW Arduino toolkit does not target the Arduino (and couldn’t since the Arduino Uno uses only an 8 bit microcontroller). Instead there is fixed C code running on the Arduino to transfer peripheral information to the serial port and back. That is, none of the LabVIEW target code executes on the Arduino. This idea is for LabVIEW code developed on a desktop to be transferred and execute on the target Arduino Due.)

 

Wouldn’t it be great to programme the Arduino Due in LabVIEW?

The current behavior of LabVIEW is as such:

 

 

The pick list of event data strips the cluster, only allowing access to the elements inside the cluster. In order to manipulate the native datatype, you must reconstitute the cluster inside the event structure, a performance hit on large data structures firing at quick event rates. This is not to mention a messy FP.

 

I suggest that User Events preserve the clustered event datatype, allowing the programmer to access to the native datatype on the consumer end. The option to select only the element "Clustered Typedef.Array of I32s" of course still remains, but is not forced upon you. (Note that the below block diagram is NOT a direct LabVIEW screenshot... brought to you by trickery and a paint program. I clustered the cluster on event datatype [not shown] so that the event structure could eat the outer layer)

 

 

My motivation with this suggestion is directly linked with my other post on the Big Typedef Issue.

Hi,

 

when I have to rework a vi, i usually start by putting the existing code in a disable structure

and then start working in the disabled 'case'.

 

Quite often I end up trying to replace the disable structure with a case structure to test the new or reworked vi.

 

Now I have to copy everyting into a temporary vi, remove the disable structure, put a case structure in place, paste again and rewire iputs and outputs.

 

Please add the ability to replace the disable structure with a case structure.

LabVIEW loops are quite flexible and allow me to do just about anything I want, but I often find myself writing the same code over and over again trying to iterate across different data types and data structures. There are several situations where smarter looping constructs could greatly simplify my code. One simple example is stepping by a delta between a minimum and maximum value. Currently, I have to calculate the number of iterations required ahead of time (for a for loop) or do a comparison with the maximum (with a while loop) and use shift registers to maintain the intermediate value. I'd like to be able to wire the max, min, and delta to my loop and have LabVIEW do the required calculations for me. The iteration terminal could also adapt to the proper data type given the input parameters. Perhaps the iteration terminal would have two outputs, one with the current iteration count and the other with the proper iteration value.

 

 

 

Another useful feature would be allowing me to wire a queue reference to the loop count terminal of the for loop and having it automatically pop each value from the queue and feed it to me through the iteration terminal. It would do this until there are no values left in the queue or until the code stops the loop. One could write an algorithm that pushes new points into the queue from within the loop or push the current value back onto the queue for later processing.

 

I'm sure there are other useful iteration strategies that are fairly common, please share them with the community. 

We currently have an option to "Run executable at the end of installation".  This is useful for installing other stuff required by your application.  However, we also need the ability to clean up these things during the uninstall process.  So, I'd like an option to "Run executable at the beginning of uninstallation".

 

I liked the new DBL on the palette that we got last year or so - saves a step. But, it should NOT adapt to entered data by default! Why would I specifically place a DBL only to have it change?