local vs. global variable

[labmaster]

I remembered some document on memory management with LV.

As a rule of thumb, local and global variable is not so good in terms of  memory management.

But I realized real programming is quite difficult to follow this rule (actually, in using separate loops like producer conisumer structure.).

I have to manage a big array of DBL in many logics in the producer loop, though I know I have to use the shift register.

Whenever I used the local variable of array, the memory will be consumed twice or three times.

However, I am wondering if there is a different between global and local variable, or functional global. 

Can you compare these things (local, global, or other I didn't use) in terms of memory and speed performance?

labmaster.

[smercurio_fc]

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@labmaster wrote:

I remembered some document on memory management with LV.

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Perhaps you are referring to this: https://www.ni.com/docs/en-US/bundle/labview/page/memory-management-for-large-data-sets.html, which is in the LabVIEW Help.

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As a rule of thumb, local and global variable is not so good in terms of  memory management.

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Not completely accurate. The issue is to reduce the number of copies of the data. Local and global variables have their use. And abuse.

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But I realized real programming is quite difficult to follow this rule (actually, in using separate loops like producer conisumer structure.).

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Then may I humbly suggest that you are not doing "real programming". Honestly, what do you expect from statements like this? A good architecture and program is not dependent on the use of local variables and/or global variables. Consequently, the use of local and/or global variables does not mean you have a crappy architecture or program.

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I have to manage a big array of DBL in producer loop.

Whenever I used the local variable of array, the memory will be consumed twice or three times.

However, I am wondering if there is a different between global and local variable, or functional global. 

Can you compare these things (local, global, or other I didn't use) in terms of memory and speed performance?

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You should be using a queue. That's the basis of the producer-consumer architecture.

[Mark_Yedinak]

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@labmaster wrote:

But I realized real programming is quite difficult to follow this rule (actually, in using separate loops like producer conisumer structure.).

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Nothing could be further from the truth. Assmercurio_fc stated, a good architecture and design will alleviate the need to rely on local and global variables. I would even argue that it is quite easy to never use a global variable. In fact, I haven't used one since the mid 90s. Even then I tried to avoid them and used them very rarely. When I use local variables they are almost always restricted to my UI code in order to read from an indicator or write to a control. And when used the necessary controls are in place to eliminate race conditions.

[altenbach]

You could also use data value references, single process shared variables, or a simple action engine. The possibilities are endless. 🙂