add missing method for rand(::_GLOBAL_RNG)
#41123
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`GLOBAL_RNG` is a relic from pre-v1.3 when our global RNG was not thread-safe: ``` const GLOBAL_RNG = MersenneTwister() ``` `GLOBAL_RNG` was never really specified, but was referred to in docstrings (of `rand` etc.), and people had to use it in packages in order to provide a default RNG to their functions. So we have to keep defining `Random.GLOBAL_RNG` for the time being. In v1.3, we didn't have anymore a unique global RNG, but instead one per thread; in order to keep code using `GLOBAL_RNG` working, we got this new definition as a clever hack: ``` struct _GLOBAL_RNG <: AbstractRNG end const GLOBAL_RNG = _GLOBAL_RNG() ``` I.e. `GLOBAL_RNG` is just a handle, which refers to the actual threaded-RNG when passed to `rand` functions. This entails defining most function taking a `default_rng()` to also accept `_GLOBAL_RNG`. See #41123, and #41235 which is not even merged. But since v1.7, we have `Random.default_rng()` (our now official way to refer to the default RNG) returning `TaskLocalRNG()`, which is itself a "handle" (singleton). So we can as well redefine `GLOBAL_RNG` to be `TaskLocalRNG()` instead of `_GLOBAL_RNG()`, with the advantage that all the relevant methods are already defined for `TaskLocalRNG`. The only expected difference in behavior is `seed!(GLOBAL_RNG, seed)`, which previously would update `Random.GLOBAL_SEED` (a hack used by `@testset`), but now is equivalent to `seed!(TaskLocalRNG(), seed)`, which doesn't update this global seed. This precise behavior was never documented (`GLOBAL_SEED` is purely internal), so this should be fine.
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`GLOBAL_RNG` is a relic from pre-v1.3 when our global RNG was not thread-safe: ``` const GLOBAL_RNG = MersenneTwister() ``` `GLOBAL_RNG` was never really specified, but was referred to in docstrings (of `rand` etc.), and people had to use it in packages in order to provide a default RNG to their functions. So we have to keep defining `Random.GLOBAL_RNG` for the time being. In v1.3, we didn't have anymore a unique global RNG, but instead one per thread; in order to keep code using `GLOBAL_RNG` working, we got this new definition as a clever hack: ``` struct _GLOBAL_RNG <: AbstractRNG end const GLOBAL_RNG = _GLOBAL_RNG() ``` I.e. `GLOBAL_RNG` is just a handle, which refers to the actual threaded-RNG when passed to `rand` functions. This entails defining most functions taking a `default_rng()` to also accept `_GLOBAL_RNG`. See #41123, and #41235 which is not even merged. But since v1.7, we have `Random.default_rng()` (our now official way to refer to the default RNG) returning `TaskLocalRNG()`, which is itself a "handle" (singleton). So we can as well redefine `GLOBAL_RNG` to be `TaskLocalRNG()` instead of `_GLOBAL_RNG()`, with the advantage that all the relevant methods are already defined for `TaskLocalRNG`. The only expected difference in behavior is `seed!(GLOBAL_RNG, seed)`, which previously would update `Random.GLOBAL_SEED` (a hack used by `@testset`), but now is equivalent to `seed!(TaskLocalRNG(), seed)`, which doesn't update this global seed. This precise behavior was never documented (`GLOBAL_SEED` is purely internal), so this should be fine.
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`GLOBAL_RNG` is a relic from pre-v1.3 when our global RNG was not thread-safe: ``` const GLOBAL_RNG = MersenneTwister() ``` `GLOBAL_RNG` was never really specified, but was referred to in docstrings (of `rand` etc.), and people had to use it in packages in order to provide a default RNG to their functions. So we have to keep defining `Random.GLOBAL_RNG` for the time being. In v1.3, we didn't have anymore a unique global RNG, but instead one per thread; in order to keep code using `GLOBAL_RNG` working, we got this new definition as a clever hack: ``` struct _GLOBAL_RNG <: AbstractRNG end const GLOBAL_RNG = _GLOBAL_RNG() ``` I.e. `GLOBAL_RNG` is just a "handle", which refers to the actual threaded-RNG when passed to `rand` functions. This entails defining most functions taking a `default_rng()` to also accept `_GLOBAL_RNG`. See #41123, and #41235 which is not even merged. But since v1.7, we have `Random.default_rng()` (our now official way to refer to the default RNG) returning `TaskLocalRNG()`, which is itself a "handle" (singleton). So we can as well redefine `GLOBAL_RNG` to be `TaskLocalRNG()` instead of `_GLOBAL_RNG()`, with the advantage that all the relevant methods are already defined for `TaskLocalRNG`. The only expected difference in behavior is `seed!(GLOBAL_RNG, seed)`, which previously would update `Random.GLOBAL_SEED` (a hack used by `@testset`), but now is equivalent to `seed!(TaskLocalRNG(), seed)`, which doesn't update this global seed. This precise behavior was never documented (`GLOBAL_SEED` is purely internal), so this should be fine.
vchuravy
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`GLOBAL_RNG` is a relic from pre-v1.3 when our global RNG was not thread-safe: ``` const GLOBAL_RNG = MersenneTwister() ``` `GLOBAL_RNG` was never really specified, but was referred to in docstrings (of `rand` etc.), and people had to use it in packages in order to provide a default RNG to their functions. So we have to keep defining `Random.GLOBAL_RNG` for the time being. In v1.3, we didn't have anymore a unique global RNG, but instead one per thread; in order to keep code using `GLOBAL_RNG` working, we got this new definition as a clever hack: ``` struct _GLOBAL_RNG <: AbstractRNG end const GLOBAL_RNG = _GLOBAL_RNG() ``` I.e. `GLOBAL_RNG` is just a "handle", which refers to the actual threaded-RNG when passed to `rand` functions. This entails defining most functions taking a `default_rng()` to also accept `_GLOBAL_RNG`. See JuliaLang/julia#41123, and JuliaLang/julia#41235 which is not even merged. But since v1.7, we have `Random.default_rng()` (our now official way to refer to the default RNG) returning `TaskLocalRNG()`, which is itself a "handle" (singleton). So we can as well redefine `GLOBAL_RNG` to be `TaskLocalRNG()` instead of `_GLOBAL_RNG()`, with the advantage that all the relevant methods are already defined for `TaskLocalRNG`. The only expected difference in behavior is `seed!(GLOBAL_RNG, seed)`, which previously would update `Random.GLOBAL_SEED` (a hack used by `@testset`), but now is equivalent to `seed!(TaskLocalRNG(), seed)`, which doesn't update this global seed. This precise behavior was never documented (`GLOBAL_SEED` is purely internal), so this should be fine.
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This caused
rand(GLOBAL_RNG)andrand(copy(GLOBAL_RNG))to take different paths, leading to a failure in DynamicHMC.jl.