Get all different values in an array - "or array elements" doesn't work with I32

[Florian.Ludwig]

Hi,

I just found out that "or array elements" doesn't work with a 1D array of integer values. I had not expected that.

I did a semi-quick forum search and didn't find a pointer to an efficient solution. Can someone give me a hint?

Taking a step back my original intent is to list all values that show up in an integer array.

I thought if I converted the numbers to powers of 2 and or array elements I had solved the problem at hand - only to find out that doesn't work.

If someone could propose a different approach I'd be happy too.

I should mention that execution time is a factor here - I need fast code, but all suggestions are welcome as they might get me started.

Regards Florian

[GerdW]

Hi Florian,

whenever you "think" of some programming you should attach atleast a picture of your VI...

This would be the simple (non-optimized) approach to filter unique values of an input array:

I really don't understand where you want to use an "OR array" or "Power of 2" function here...

[Florian.Ludwig]

Thank you for posting GerdW,

you are right of course - I thought I had nothing to show. But pictures speak more than 1000 words.

I thought this would be the easiest code to find out what values the array produced and pretty efficient at that:

I should mention that I don't have to cover a huge range of numbers - so wasting space by upconverting the numbers to powers of two isn't an issue.

Your vi gave me an idea - I could make a bucket brigade version of that. That wouldn't be a bad start.

Regards Florian

[GerdW · Accepted solution]

Hi Florian,

try that:

It seems the OR array" function is polymorph (as written in the context help), but doesn't handle I32 arrays. Atleast the error message implies just that...

[Florian.Ludwig]

Hi GerdW,

I tried that - and guess what: A benchmark showed it is the fastest solution!

I must admit I had dismissed the simplest solution because I thought I could come up with a custom made solution with the info I had about what my input array would look like.

Simplicity rules, and you should never guess when it comes to performance. A benchmark has to be made!

Seems like the "or array elements" only works with different dimensions of Boolean arrays.

Regards

Florian

[crossrulz]

It is usually best to just keep it as simple as possible.  What do you think the code in the OR Array Elements does?  I imagine it is just a simple FOR loop with a variable to keep the latest OR.  So I would do what GerdW just showed with the FOR loop.

[Florian.Ludwig]

You definitely have a point there.

I thought that the primitive might be faster though maybe due to some internal optimization that reduces loop overhead.

Additionally as I am an engineer turned programmer I couldn't dismiss the possibility there is an algorithm to mass OR more efficiently than just looping through it all that I am not aware of.

Like stopping to care for bits that already turned out as a 1 in previous iterations or something.

Also, there are some qualities to my input data that would take some time to explain which made me think I could optimize the algorithm (like numbers will mostly be in blocks etc.).

Regards

Florian