"Loop invariant code motion" Did you know this and why didn't you tell me?

[Ben]

I'll provide the answer if nobody replies but I'll let y'all discover this yourself.

Have fun,

Ben

[Ben]

Hint:

"Loop invariant code motion" invalidates suggestion we often suggest to people trying to optimize the perfomance of their loops.

Ben

[GerdW · Accepted solution]

Hi Ben,

thanks for having Wikipedia

And: No, I wasn't aware of something like this in LabVIEW... And I always move constant code outside of loops...

[Ben]

And we have a winner for this afternoon's game!

For those that do not have access to the Wiki...

If the LV compiler "sees" you have code in a loop that produce the same answer for every iteration it CAN move that code to execute before the loop.

Ben

[Broken_Arrow]

If the LV compiler "sees" you have code in a loop that produces the same answer for every iteration it SHOULD throw up a dialog that says "IDIOT!"

[JÞB]

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Ben wrote:

If the LV compiler "sees" you have code in a loop that produce the same answer for every iteration it CAN move that code to execute before the loop.

Ben

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I assume this only works with debugging off in a manner similar to the removeal of structures with no outputs.  can you confirm?

Also a link to your source would be nice-  I'd like to know a bit more about this compiler feature.

[elset191]

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Ben wrote: 

If the LV compiler "sees" you have code in a loop that produce the same answer for every iteration it CAN move that code to execute before the loop.

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Can, or does?

[GregFreeman]

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elset191 wrote:

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Ben wrote: 

If the LV compiler "sees" you have code in a loop that produce the same answer for every iteration it CAN move that code to execute before the loop.

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Can, or does?

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Just what I was about to ask.

[Ben]

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elset191 wrote:

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Ben wrote: 

If the LV compiler "sees" you have code in a loop that produce the same answer for every iteration it CAN move that code to execute before the loop.

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Can, or does?

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I softened the first post but after a re-read it DOES.

The only reference I have is "LabVIEW Performance 2009 Course Manual" Part number 325501A-01 April 2010 Edition, Page 1-32."

Ben

[JÞB]

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Ben wrote:

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The only reference I have is "LabVIEW Performance 2009 Course Manual" Part number 325501A-01 April 2010 Edition, sample here

Page 1-32."  is not encluded in the sample

Ben

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Any other neat features hidden in the manual- or do I need to by the class