Use const& instead of const where applicable

[masterleinad]

This results from a recent clang-tidy run. Use const & instead of const were applicable.

[Rombur]

Personally, I don't like this. Why would we want to pass a shared_ptr by reference? There is also no point in making the shared_ptr constant, what matters is what the shared_ptr points to.

[masterleinad]

This way we avoid increasing and decreasing the counter though.

[tjhei]

This way we avoid increasing and decreasing the counter though.

Not that the performance of it matters here, but a shared_ptr needs to do refcounting in a threadsafe manner (mutex or atomic operations), so it is not "cheap". I agree that passing by reference here is cleaner.

[tjhei]

/run-tests

[Rombur]

Not that the performance of it matters here, but a shared_ptr needs to do refcounting in a threadsafe manner (mutex or atomic operations), so it is not "cheap"

It is cheap compared to the MPI communication that the function does.

[bangerth]

Nice!
OK to merge once the tester is happy.