Optimise from_rng & try_from_rng methods for RapidRng - #2
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Bluefinger
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Aug 31, 2026
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| fn try_from_rng<R: TryRng + ?Sized>(rng: &mut R) -> Result<Self, R::Error> { | ||
| match rng.try_next_u64() { |
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This is just unsugared ?, mostly done this way to optimise dev compile times to keep them fast. For release mode, it all gets optimised pretty well anyway and makes small difference to compile speed. Runtime speed should be the same.
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The default method implementations for
SeedableRngusefill_byteswhich works well as a default, but is not the optimal path for a PRNG likeRapidRng.fill_bytesworks well for larger buffer sizes, but for a smaller state, it doesn't optimise well as[u8; 8]lacks alignment information thatu64has. Thankfully,next_u64()can be used to directly create theRapidRngstate, bypassing a lot offill_bytesmachinery and being a lot easier for the compiler to optimise.