Call RandomNumberSeed() on-demand (#33539)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33539
We rarely use the `random_seed_` in context but we always initialize it with `RandomNumberSeed()` which isn't trivial. This diff makes it that we only call `RandomNumberSeed()` once when we want to use `random_seed_`.
Test Plan:
unittests.
Canaries:
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Reviewed By: ipiszy
Differential Revision: D19993190
fbshipit-source-id: 1d2606bd65476ff3b519c69f9cbfa3b80f75cdff
