About dot notation for pre-allocated values a .= f.(x)

[nilshg]

Not an answer, but there was a similar report (although in the specific context of an Any array) a few days ago here:

Why is identity on an Any vector so much slower when broadcasting than when mapped?

In the REPL I was experimenting with a function that returns Vector{Any}, and I wanted to see how I could make Julia “automatically” change the type to a fixed type without having to specify it myself. I noticed that even though the end result is the same, the performance can vary widely depending on how I do it. I found a simple example that shows an extreme difference: (I’ll suppress the outputs of the vectors because they’re long) julia> s = Any[i for i in 1:10000] # 3 different ways to do…

I’d be keen to have an answer to your question myself.