# Multicore with opam--instructions?

**URL:** <https://discuss.ocaml.org/t/multicore-with-opam-instructions/10548>\
**Category:** Ecosystem\
**Tags:** opam\
**Created:** [September 29, 2022, 7:31pm UTC](https://discuss.ocaml.org/t/multicore-with-opam-instructions/10548 "2022-09-29T19:31:47Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![dbuenzli](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/dbuenzli/32/18_2.png) [@dbuenzli](https://discuss.ocaml.org/u/dbuenzli)\
**Post date:** [September 29, 2022, 8:03pm UTC](https://discuss.ocaml.org/t/multicore-with-opam-instructions/10548/2 "2022-09-29T20:03:04Z")

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> [@yawaramin](#):
>
> EDIT 2: ptime and all its reverse deps failed to install.
> 
> Error log: `Error: .../ocamlbuild_plugin.cmx was built with -for-pack Ocamlbuild_pack, but the current unit Myocamlbuild is not`

You will need [Package ocamlbuild.0.14.2 by kit-ty-kate · Pull Request #22182 · ocaml/opam-repository · GitHub](https://github.com/ocaml/opam-repository/pull/22182)

Everything should be fine on [5.0.0 though](http://check.ocamllabs.io/?comp=5.0&comp=5.0%2Balpha-repo&available=5.0&available=5.0%2Balpha-repo&show-only=good&show-only=partial&show-only=bad&show-only=not-available&show-only=internal-failure&show-latest-only=true&maintainers=&logsearch=&logsearch_comp=4.02). If I were you, I’d rather go with the [5.0.0 line](https://discuss.ocaml.org/t/ocaml-5-0-zeroth-alpha-release/10026) than trunk which is always bound to be more brittle.

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