Zero breadth warning can be improved

[lhstrh]

We currently have this warning message:

Reaction graph breadth is computed to be 0. Indicates an error.

Perhaps it makes more sense to report something less cryptic, like No reactions in this program.

[erlingrj]

Agreed. Should I also add the smarter-default-number-of-workers to the Cpp target?

[lhstrh]

Should I also add the smarter-default-number-of-workers to the Cpp target?

The dependency graph is constructed at runtime in reactor-cpp, so I doubt that if we want this feature for the C++ target we'd want it implemented at compile time. That said, I think that @cmnrd should comment on this :-)

[cmnrd]

I am not sure what exactly 'smarter-default-number-of-workers' refers to, but indeed we shouldn't aim at statically setting the number of workers in C++. Currently, the C++ runtime default is to use as many workers as there are hardware threads on the machine executing the program. If there is evidence that a more complex strategy brings significant benefits, I would be happy to accept a PR that implements this strategy in reactor-cpp.

[cmnrd]

Should we close this? Looks like there is an associated merged PR.