I guess it's your implementation's problem. I faced the same but changed something in data structure and now it works. I'm sure it's because function composition and matrix multiplication are non-commutative so the order of evalutation should be preserved.

I didn't have problems with min though.

I tried your solution and I get:
"Expected: equal to 22
Actual: 16".
So writing "...if no output to cout or cerr is getting actually written in test reports" is wrong.
What more do you want?

BTW you fail the first test "dotest(10, 22);". In this case you have the input, you have "actual", you have "expected" and, in addition, you have the corresponding exemple in the description: "Ex: u = [1, 3, 4, 7, 9, 10, 13, 15, 19, 21, 22, 27, ...]"... so you have everything you need to debug your code.

There exist many comments amounting to the same message as yours.
They are almost all about an incorrect observation. You're going to get an identical answer/reference to existing answers unless you add more information so that it is no longer the same comment as those others.

If you provide a way to reproduce your observation (your code), others can point out the problem. Better for everyone.

That's because you're reading the logs incorrectly. Take 1 minute and have a look at hundred other comments with similar questions.