Adding explanation to seeded rng used in examples

[andristarr]

Objective

• Fixes Explain the usage of seeded RNG in examples #12544

Solution

• Added/updated a universally worded comment to all seeded rng instances in our examples.

[BD103]

Suggested change

	// Make it play out the same way every time with deterministic results. We do this for testing purposes.
	// Make it deterministic for testing purposes.

I personally don't like "make it play out" as a phrase. I feel like determinism is a common enough term, or at least easily googled, so it should be enough to just say that.

[andristarr]

Done!

[BD103]

Thanks!

[Bluefinger]

If we are emphasising that the seeded rng is being used for deterministic purposes, then we kinda shouldn't be using StdRng in the first place. StdRng is documented as being deterministic in output, but not portable, so there is no assurance that the output will be the same on different platforms or different versions of rand. And if we are testing across different platforms, we'd then expect the output to match across all platforms. For further reference from the rand documentation, their documented expectations for portability/determinism.

Given rand minor versions might in the future change the underlying algorithm for StdRng, end users might find their tests breaking if they used StdRng in their tests after basing them on our examples. Better to instead encourage using the algorithm crates directly if they want to have that extra assurance in determinism. Currently, rand_chacha is what is the underlying algorithm for StdRng, specifically ChaCha12Rng. For game dev purposes, ChaCha8Rng would be a better fit to provide higher throughput at the expense of some entropy quality (though it will still be far better than what is probably required).

[andristarr]

So this PR should be abandoned I assume?

[Bluefinger]

So this PR should be abandoned I assume?

Up to you. Personally, I would just merge this as an easy docs change (since the comments in the PR are correct with intent), then follow-up with the more extensive changes.

[andristarr]

Merge it from my opinion then as well!

[james7132]

Suggested change

	// Make it deterministic for testing purposes.
	// We're seeding the PRNG here to make this example deterministic for testing purposes.
	// This isn't strictly required in practical use unless you need your app to be deterministic.

This may need to be reflected on the other examples.

[andristarr]

Do you want this exact wording for all instances? I feel its a little bit verbose.

[james7132]

It is, but explaining the full reasoning is probably for the best.

[BD103]

Can this PR update from main, now that #12644 is merged? (There should be a button on Github, or you can run git merge main after pulling the main branch locally.) We've switched to ChaCha8Rng, so I want to make sure there are not any conflicts.

[andristarr]

Merged main in, it should is up to date now!

[james7132]

@alice-i-cecile I think the above comment about rewording it should be addressed before merging. This is otherwise a bit light on why it's being done.