optimizing a vi

[irfocus]

Could anyone give a little advise on how to optimize the attached vi.  This is a sub VI wherein I send in a image ROI Global Rectangle and a full data array.  I want to grab only a section of that array (specified by the Global Rectangle) and send it back.

This Sub VI works but it is prohibitively slow (as much as a second).  I tried a few other methods in the hopes that the nested for loop was inherently slow.  All methods I tried are also slow.  There must be an efficient (fast) way to do this since there is not much to accomplish.

Any suggestions

[Photon_Dan]

1.  Bring your controls outside the loops.  Leaving them inside forces the execution to check the UI for changes on every iteration.
2.  Avoid using the Value attribute to write a new value to a control within the same VI.  It is OK to use that for updating values on other VIs only if it is done occasionally, but certainly not in a For loop.
2.  Try to maintain consistent data types, those little red dots represent conversion which means data copies being made behind the scenes.

I did a quick refactor of your VI.  See if it meets your needs.

Are you using a FLIR A-series?  We are using those on a project right now.

Dan Press

Certified LabVIEW Architect

PrimeTest Automation

Message Edited by Photon Dan on 07-20-2009 02:59 PM

[altenbach]

I addition to the above:

• Don't use controls as initializers, use plain diagram constants. You min, max and mean are not needed.
• Your shift registers have no functionality at all. Accumulate the data in shift registers instead. No property nodes needed.
• WHy do you need three diagram constants of 273.15. One is enough! Don't be afraid to branch a wire!

You could just reshape and take a subset, e.g. as follows:

Message Edited by altenbach on 07-20-2009 01:44 PM

[altenbach]

If you want to use two loops (maybe it's more efficient in memory?), simply correctly initialize the shift registers:

zero for the ave

Inf for the Min

-Inf for the Max

Here's a quick draft.

Message Edited by altenbach on 07-20-2009 02:21 PM

[abasani]

Good day Photon Dan,

Could you please further explain the following " 2.  Avoid using the Value attribute to write a new value to a control within the same VI.  It is OK to use that for updating values on other VIs only if it is done occasionally, but certainly not in a For loop."

or kindly direct me to an article or notes about this .

Regards

Abasani

[Photon_Dan]

See this section of the LabVIEW help.