On my bit old Gentoo linux machine,
$ nim -v
Nim Compiler Version 0.20.2 [Linux: amd64]
Compiled at 2019-07-30
Run
C++: 3.4269
nim c -r -d:release seqbench.nim
6.683s
nim c -r -d:danger seqbench.nim
6.986s
nim cpp -r -d:danger seqbench.nim
7.011s
nim c -r -d:danger --gc:none seqbench.nim
3.922s
nim c -r -d:danger --newruntime seqbench.nim
5.769s
Run
According to this document,
[https://nim-lang.org/docs/gc.html](https://nim-lang.org/docs/gc.html)
> The GC is only triggered in a memory allocation operation. It is not
> triggered by some timer and does not run in a background thread.
Your code allocate heap memory inside the loop. It seems GC is a bottleneck.
