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Clarify status of RNG being thread-safe #46280

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Clarify status of RNG being thread-safe #46280

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Clarify status of RNG being thread-safe
alecloudenback Aug 8, 2022
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alecloudenback Aug 12, 2022
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Merge branch 'JuliaLang:master' into master
alecloudenback Aug 24, 2023
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alecloudenback Aug 24, 2023
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alecloudenback authored Aug 12, 2022
commit f1f59003864e4a304f301105524ba605aa037f1b
2 changes: 1 addition & 1 deletion stdlib/Random/docs/src/index.md
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Expand Up @@ -18,7 +18,7 @@ The PRNGs (pseudorandom number generators) exported by the `Random` package are:
Most functions related to random generation accept an optional `AbstractRNG` object as first argument.
Some also accept dimension specifications `dims...` (which can also be given as a tuple) to generate
arrays of random values.
In a multi-threaded program, you should generally use different RNG objects from different threads or tasks in order to be thread-safe. However, the default global RNG is thread-safe as of Julia 1.3 (using a per-thread RNG up to version 1.6, and per-task thereafter). The global RNG refers to per-thread RNG instances; If you instantiate a non-global RNG, you should create a new RNG instance for each thread to avoid possible data-races.
In a multi-threaded program, you should generally use different RNG objects from different threads or tasks in order to be thread-safe and deterministic (if given a specific seed). However, the default global RNG is thread-safe as of Julia 1.3 (using a per-thread RNG up to version 1.6, and per-task thereafter). The global RNG refers to per-thread RNG instances; If you instantiate a non-global RNG, you should create a new RNG instance for each thread to avoid possible data-races.
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The

The global RNG refers to per-thread RNG instances; If you instantiate a non-global RNG, you should create a new RNG instance for each thread to avoid possible data-races.

seems like it is just saying the same thing as the earlier stuff in the paragraph again?

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Here was my confusion so maybe there's a clearer way to get this across. Per the prior docs:

  1. The global RNG is thread safe
  2. Xoshiro is used as the global RNG
  3. Therefore, if I use a newly instantiated Xoshiro (call it X), I can have code in multiple threads reference X without issues.

#3 is not correct because the Global RNG is constructed in a way that makes it thread safe and that's the point that I don't think comes across previously and what

The global RNG refers to per-thread RNG instances; If you instantiate a non-global RNG, you should create a new RNG instance for each thread to avoid possible data-races.

Is trying to differentiate from what was stated before.

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I tried to clarify in the latest commit


The provided RNGs can generate uniform random numbers of the following types:
[`Float16`](@ref), [`Float32`](@ref), [`Float64`](@ref), [`BigFloat`](@ref), [`Bool`](@ref),
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