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@testset: with Xoshiro, restore Random.GLOBAL_SEED #43188

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merged 1 commit into from
Nov 23, 2021
Merged

@testset: with Xoshiro, restore Random.GLOBAL_SEED #43188

merged 1 commit into from
Nov 23, 2021

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rfourquet
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A @testset is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before Xoshiro as the default RNG, the "global seed" was stored
within a MersenneTwister object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.

@rfourquet rfourquet added backport 1.7 bugfix This change fixes an existing bug testsystem The unit testing framework and Test stdlib labels Nov 22, 2021
@Seelengrab
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Does this possibly fix #42752?

@rfourquet
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Does this possibly fix #42752?

Probably not, but who knows?... I noticed the bug fixed by this PR while looking at that issue, but I don't understand the cause of it.

@rfourquet
@testset: with Xoshiro, restore Random.GLOBAL_SEED
e53b1b9 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.
jonas-schulze
jonas-schulze reviewed Nov 22, 2021
View reviewed changes
stdlib/Test/test/runtests.jl
@test GLOBAL_SEED_orig == Random.GLOBAL_SEED
@testset "GLOBAL_SEED is also preserved (beginend)" begin
@test refvalue == rand(Int)
end
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Suggested change
end
end
@test GLOBAL_SEED_orig == Random.GLOBAL_SEED

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Thanks, yes this could be added, but this is also tested after the first testset of the series, which is also "beginend" (actually, this last testset really is testing that the forloop one correctly restored the global seed by checking rand(Int) within it, but it's a bit redundant with @test GLOBAL_SEED_orig == Random.GLOBAL_SEED just before it; but as we don't call seed! there, there is not much need to recheck this equality after it).

@vtjnash
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vtjnash commented Nov 22, 2021

Would it be better if we called seed! here instead? (possibly without the copy, or do the copy next)

@rfourquet
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Would it be better if we called seed! here instead? (possibly without the copy, or do the copy next)

It would work too, but we would indeed need to still make the copy to restore the global rng, which doesn't necessarily correspond to the pristine state after seed!(GLOBAL_SEED). I prefer set_global_seed! as it's no less cheap than needed, compared to seed!, and more to the point. To avoid introducing this function, making GLOBAL_SEED a Ref{Any} might work, but I'm not sure whether this would be safe w.r.t. multithreading.

@rfourquet rfourquet added the randomness Random number generation and the Random stdlib label Nov 23, 2021
@vtjnash vtjnash merged commit 08ea2d8 into master Nov 23, 2021
@vtjnash vtjnash deleted the rf/testset-GLOBAL_SEED branch November 23, 2021 15:41
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vtjnash commented Nov 23, 2021

Does this bug need to be fixed inside Test.guardseed too?

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No, guardseed is dead code, I've been meaning to remove it. But it's interesting that the "bug" in #42752 was found thanks to guardseed's tests.

@KristofferC KristofferC mentioned this pull request Nov 25, 2021
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KristofferC pushed a commit that referenced this pull request Nov 25, 2021
@rfourquet @KristofferC
@testset: with Xoshiro, restore Random.GLOBAL_SEED (#43188)
e1c7cd4 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.

(cherry picked from commit 08ea2d8)
KristofferC pushed a commit that referenced this pull request Nov 26, 2021
@rfourquet @KristofferC
@testset: with Xoshiro, restore Random.GLOBAL_SEED (#43188)
5a99507 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.

(cherry picked from commit 08ea2d8)
KristofferC pushed a commit that referenced this pull request Nov 26, 2021
@rfourquet @KristofferC
@testset: with Xoshiro, restore Random.GLOBAL_SEED (#43188)
bf8d60b 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.

(cherry picked from commit 08ea2d8)
LilithHafner pushed a commit to LilithHafner/julia that referenced this pull request Feb 22, 2022
@rfourquet @LilithHafner
@testset: with Xoshiro, restore Random.GLOBAL_SEED (JuliaLang#43188)
cd6c3a0 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.
LilithHafner pushed a commit to LilithHafner/julia that referenced this pull request Mar 8, 2022
@rfourquet @LilithHafner
@testset: with Xoshiro, restore Random.GLOBAL_SEED (JuliaLang#43188)
b4f7da0 
A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.
vchuravy pushed a commit to JuliaLang/Test.jl that referenced this pull request Oct 7, 2023
@rfourquet @KristofferC
@testset: with Xoshiro, restore Random.GLOBAL_SEED (JuliaLang/julia…
a1f51b3 
…#43188)

A `@testset` is supposed to restore the "global RNG state" as
it was before execution (so that they can be re-ordered easily, etc.)
Also, before a testset starts, the default RNG is re-seeded with the
"global seed" (to help reproduce test failures).

Before `Xoshiro` as the default RNG, the "global seed" was stored
within a `MersenneTwister` object. It was enough for a testset to
copy the default RNG at the start, and copy it back at the end.
But now the global seed is stored outside of the RNG, so it should
also be restored separately.

(cherry picked from commit 6b48dc1)
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