support for bool via kabool wrapper

[niklas-uhl]

This fixes #219

[kurpicz]

I really like this proposal. However, there are a few things like to be added:

• Tests for at leas one other MPI operation currently available in KaMPI.ng
• automatic conversion (with runtime overhead) from std::vector<bool> to std::vector::<kabool>

[niklas-uhl]

automatic conversion (with runtime overhead) from std::vector<bool> to std::vector::<kabool>

I don't like automatic conversion from std::vector<bool> to std::vector<kabool>, because it involves copying. With the current interface, it becomes clear to the user that this has a runtime overhead, and the user gets a hint on whether it is preferable to represent the data as std::vector<kabool> throughout the whole application when he has to type:

std::vector<bool> data = {...};
std::vector<kabool> data_to_send {data.begin(), data.end()};

[Hespian]

It might be a topic to be discussed with all developers but I agree that automatic conversion would be nice.
At least using send_buf(false) should probably work (not sure if it does right now)

[niklas-uhl]

send_buf(false) is against our current API design, because we don't have single element receive buffers yet and the type of the output buffer is infered from the input type. When I input send_buf(false) the receive buffer is a std::vector<bool> of size 1, which is not compatible with MPI, so we have to also do implicit conversion of the result. That makes it even worse, when we allow passing std::vector<bool> as send_buf and do implicit conversion, we will implicitly copy an arbitrarily sized user input twice. We could mention this in the docs, but then we have weird corner cases, where we incur runtime overhead. From a user perspective its much easier to understand, that you should just not use bool, but wrap it. This is already ergonomic enough because of the implicit conversion bool <-> kabool

[Hespian]

Add tests for make_data_buffer and possibly for the buffer factories. I think these are more important than the many tests for some operations that you added. They should just work if the buffer factories work.

[Hespian]

I know it's annoying, but OwnContainer has do much non-trivial code that I think it should have tests.