200-600x slower Dlang performance with nested foreach loop

[Paul Backus]

On Wednesday, 27 January 2021 at 14:15:26 UTC, FeepingCreature 
wrote:
>
> Associative arrays allocate per entry added?!
>
> https://github.com/dlang/druntime/blob/master/src/rt/aaA.d#L205 
> Oh God, associative arrays allocate per entry added!

Maybe it's to avoid invalidating the result of `key in aa` when 
adding or removing entries? The spec doesn't say anything about 
it either way [1], but allowing invalidation would make AAs much 
more difficult to use in @safe code.

[1] https://dlang.org/spec/hash-map.html