ericphanson/allocarrays.jl

Arrays that use a dynamically-scoped allocator

allocarrays.jl's Issues

Possible memory safety features

We could include a mutable field in each AllocArray tracking whether it is active, and a vector in the bumper allocator object collecting all of the allocated arrays. Then when we reset the bump, we loop through and mark each array as inactive (which would cause eg getindex to error if called on it), and empty the list.

I think this would prevent “use after free” errors pretty comprehensively (in the serial case), possibly at the cost of some performance. It could be done as secondary types though, allowing debugging/testing with the safe version, then switching to the unchecked one for speed.

For concurrency safety, maybe some mechanism could be used for the resetting function to get exclusive access to each of the arrays in order to flip their activity bits. Eg if each array holds a lock? Or something where operations on the array don’t contest each other, but do contest with the resetter. Then we could empty the buffer once every array has been toggled inactive.

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Questions

Hi,

It's an intriguing approach. I see you take over similar, basically "malloc" for Julia... and you reduce allocations, but the timing is still worse. Is that maybe not in general, since that's the whole point?

I like Bumper, since there are no allocations, basically, so I'm confused why you have any at all? Probably for the output array.

Taking over similar seems clever, should it ideally be done too for zeros, ones (and fill?) or does it in fact happen implicitly? I'm thinking though, should it happen in all cases, and what you do is I think so-called type-piracy, so it's all or nothing?

I suppose this does not work for GPUs despite me seeing something Flux related. And neither Bumper.jl... but do you think it would be plausible?