[Nix-dev] nix.buildCores and determinism

[zimbatm]

I think there is a misunderstanding, the hash of the package derivation
depends on the build output. We assume it's always the same which allow us
to look it up based on the input hash but it's not always true. For example
if the build adds the current time to the build output it will not always
be the same.

On Tue, 11 Oct 2016, 02:48 Domen Kožar, <domen at dev.si> wrote:

> You're running the build system in parallel. For example Makefiles, they
> are not pure and thus builds can fail due to race conditions.
> We have quite a few disabled for that reason and also that's why you have
> to explicitly enable parallel building.
>
> On Tue, Oct 11, 2016 at 1:56 AM, Ruben Astudillo <ruben.astud at gmail.com>
> wrote:
>
> On reading `nixos-option nix.buildCores`, it says that this option can
> affect the determinism of the build. I don't understand how is important
> as the hash of the package depends on the default.nix file, not the
> build process. What does it mean to be non-deterministic in this case?
>
> -- Ruben Astudillo
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