Who or what tell you it's a learning test ? It is a pretty weak asumption.
The publication says nothing on the actual past experience of the developers in every language. They might very well be experienced in Go or Java.
From their C++, It is pretty obvious it is not their main language.
In my experience, this kind of code of nested shared_ptr everywhere is pretty typical of developers with a Java background just starting C++.
C++ can shine here - and still looking nearly like the go or Java-Code (due to the simple algorithm) but some one tried to write highly sophisticated code (there is no tutorial or book about C++ that teaches you to do it that way) with the result that C++ is far more slower then possible - we definitly not talking about 10% gain here
> C++ can shine here
And my point is: it didn't. And it didn't because of the learning curve involved. It's only the better solution if the knowledge is invested in ahead of time, and if the gains don't outweigh those you'd get from Go by an amount that greatly exceeds the time invested to net them, then it's not the better choice.
I agree with you that writing C++ is harder than writing Go and that writing naïve C++ leading to disproportional pessimization of your program shows that it's not the right tool for people who lack the knowledge to use it.
At the same time it's really not hard to translate simple concepts into simple code for lower-level languages, that runs well on modern processors. Basic usage of (possibly) growable, homogenous arrays will get you far. Contrary to what most C++ app developers seem to think custom allocators aren't complicated either, and will guarantee that you get much better cache locality and memory management.
Most of these issues are made hard by people, including the premise of learning the basics of what you need to do for the processor to execute your code fast.
No. Because it's not just a performance comparison, really. Without realising it, it's also a learning test. The very fact they wrote sub-par C++ code, likely without realising it, and then proceeded to produce (sub-par?) Go code that was faster demonstrates the difficulty of one language over the other. It demonstrates the cognitive efforts required between the two options and one of them was easier to produce and the results were more than suitable.
These technology comparisons are important, for sure, but at the end of the day people want an ROI from everything they do, even the things that don't involve money. So if something can be solved in six hours with one solution or 36 hours with another, and the latter only yields a 10% performance, then I'd rather my end goal be ready and "in the market" for 30 hours ahead of the other guy using the slower solution for a 10% speed improvement.