CPU issue with one of my modules

Development
1

Here’s the issue

Source code

As the issue says, if you load the module in a new patch, no problem. If you quit Rack and reopen it, the CPU usage jumps up to ~30%. Is this a Rack issue or do I something wrong in my code?

1 Like
2

I don’t understand why, but changing your internal counter reset to:

sr = sr+1;
if (sr > srIncrement){
    sr = 0;
}

seems to fix it?

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3

That’s a shame. I was planning to use that module extensively during Psychedelic December.

4

Thank you. I guess modulo is apparently really expensive. I found this discussion on stackoverflow where they measured it to be over 6x as slow: https://stackoverflow.com/questions/15596318/is-it-better-to-avoid-using-the-mod-operator-when-possible

But it is weird that it seems ok at first and then blows up after reloading rack.

update: @hamptonio did you happen to try:

sr >= srIncrement

When I use >= it makes the CPU jump up again. So weird, any ideas?

5

Oh don’t worry. I’m going to fix it and it’ll go out when they do the next build.

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6

My ancient article on efficient plugins mentions this, sort of “It used to be that division was slow, and all the transcendental functions (sine, exp, etc) were very, very, slow.” I guess division slowness still matters.

Here’s the article: [https://github.com/squinkylabs/SquinkyVCV/blob/main/docs/efficient-plugins.md]

7

I don’t think the issue here is how slow a modulus operation is. There is no way that causes 50% cpu usage. I think somehow the the check is failing (I don’t know how) and the image processing code is getting run every process call.

8

Thanks @Squinky I’ve actually read through some of that a while ago but will definitely go through it again.

1 Like
9

Yes, I would tend to agree with you.

10

That seems to make sense. Although I can’t understand why when you first load the module in a patch it works fine (and even ~1%). Well at least it’s working though, thanks again for your help.