Using most of a computers memory with a single Vec of unknown size



I’m working on an algorithm that uses large amounts of memory.
Most of that is consumed by a single Vec of small elements. There is no way to estimate its size beforehands.

In some cases, the Vec starts out on a lucky size, that when it doubles its capacity ends up using most of the RAM, say 220GiB/256GiB. Then, the algorithm runs successfully.
But sometimes it starts at a size where it doubles to 300GiB/256GiB, which cannot be allocated. In this case, the effective limit is 150GiB.

Is there a way to make the Vec alloc all the memory available before it fails?
Or, on another thought, a way to create a Vec like Vec::with_capacity(usize), but with a Result as return value instead of panicing on failed alloc?


There is Vec::try_reserve, but it’s unstable.


Ah thank you. I did not know about this.
It’s fine that it’s unstable, since I work with nightly anyways.