opam install on Apple M1/M2

[derekchiang]

Hi @lukstafi, I'm running into issues with installing Ocannl on an Apple M2 Macbook Air (OSX 15.4.1).

Running opam install neural_nets_lib results in:

[ERROR] Package conflict!
  * Missing dependency:
    - neural_nets_lib → arrayjit <= 0.4.0
    not available because the package is pinned to version 0.5.3
  * Missing dependency:
    - neural_nets_lib → arrayjit >= 0.4.1 → metal
    unknown package

No solution found, exiting

Compiling from source worked as expected.

[lukstafi]

The core problem is that ocaml-metal aka. metal disappeared: https://ocaml.org/p/metal/latest returns 404, https://github.com/ocaml/opam-repository/tree/master/packages/metal also 404.
ocaml/opam-repository#27858 added it.

[lukstafi]

But the version of OCANNL / neural_nets_lib supporting Metal is 0.5.3 and it is not released to the opam repository yet.

There is much progress on OCANNL 0.6, and it brings significant changes, but it's still a few weeks from a release.
Also unfortunately OCANNL will only be fast enough for non-toy examples at version 0.8 0.7, and will become speed-competitive at version 0.9 0.8. Apologies for the disappointment... (Edit: I'm promoting a former version 0.7 to 0.6.x.)

[lukstafi]

I'll release metal.0.1.1 where I'll vendor the runtime from camlkit instead of depending on camlkit to reduce the dependency cone -- camlkit is pretty big on the whole and we only need the runtime aka. objc.

[derekchiang]

Ok thank you Lukasz -- if 0.6 is going to fix this don't worry about rushing out the 0.5.x. I'm unblocked for now by compiling from source.

[lukstafi]

Although it will not solve the problem of ease of working with OCANNL, I'll close this issue as soon as ocaml/opam-repository#28204 is merged, since that was the root cause of the specific error message.

[lukstafi]

Like I said, OCANNL itself is not ready for prime time so the theme of this issue is not resolved, but metal is alive again: https://ocaml.org/p/metal/latest
(Pity it's No Docs, another problem to look into...)