Setting array length without initializing/reallocating.

[Dukc]

On Sunday, 13 December 2020 at 20:03:46 UTC, Jackson22 wrote:
>> No bounds checking. That slice can extend into memory that 
>> isn't of that type or even allocated to the process.
>
> No *automatic* bounds checking != no bounds checking.
>
> There's a reason .ptr exist, I wish people would stop 
> pretending that using it where it is appropriate is somehow 
> going to lead to failure when there are more successful 
> programming languages that have zero automatic bounds checking.

Yes it's possible to without automatic bounds checks. Sometimes 
one has to -when using those older langages or doing very 
low-level system programming. And other times it may not be 
necessary, but still worth it to gain that last bit of 
performance when optimizing. These are the reasons why `.ptr` 
exists.

We really don't know whether either of those cases apply to OP:s 
case, but if the length extension with implicit duplications were 
even close to the desired performance, it seems unlikely.

>
> Why did you quote expensive? Are you implying it isn't 
> expensive? Are you saying re-allocating 4 GB of memory every 6 
> ms isn't expensive?

I think he was comparing to extending the array in-place, but in 
a bounds-checked way.