Turing.jl: Remove customised `dprintln` logging function

[xukai92]

[willtebbutt]

So that it doesn't get lost, I suggested in #469 that we should use Memento.jl for our logging, as it is substantially more feature-ful than the stdlib logging, and Invenia are committed to supporting it.

[xukai92]

Thanks Will - Memento looks cool. Is there a list of what the stdlib logging can't do but Memento.jl can? I wonder whether in this stage we need a lot of features - seems that @debug, @info, @warn and @error from the stdlib is all we need.

[willtebbutt]

Not sure. @omus @iamed2 is there a canonical reference for @xukai92 's question above?

[iamed2]

There isn't yet, but I should write one. The only thing that stdlib logging offers is zero-overhead debug logging. In Memento if you log something but filter it out, there is a small cost for checking the levels. In stdlib logging, you pay a similar cost except for debug logs, which are compiled out by default.

[xukai92]

We decided to use the stdlib for now - mostly because of the simplicity + we don't need one more dependency for Turing.jl.

We can always change it to Memento.jl later if needed.

[xukai92]

Commits from f2dba79 to 3d1ea43 resolve this issue. We shall close it after the whole PR (https://github.com/TuringLang/Turing.jl/pull/469) is merged.

[trappmartin]

It's all set for the #469 to be merged soon. Therefore, closing this issue.