Do you know what you are doing?
vec.setLen(10000000)
Run
set the length and actual position to the end. This means that next add() adds
at position 10000000, not at position 0, so reallocations may occur. Maybe use
newSeqOfCap() or setLen(0).
I made a similar mistake when I started with Nim, and additional did my test
with different elements sizes:
> [https://forum.nim-lang.org/t/1964#12211](https://forum.nim-lang.org/t/1964#12211)
Generally, Nim's add() should have the same performance as C++ push-back()
nearly.
