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Fix Difference hash seed widening on 32-bit (UInt == UInt32) #688

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Fix Difference hash seed widening on 32-bit (UInt == UInt32) #688

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2 changes: 1 addition & 1 deletion src/difference.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -38,4 +38,4 @@ Base.nameof(::Difference) = :Difference
function Base.:(==)(D1::Difference, D2::Difference)
return isequal(D1.t, D2.t) && isequal(D1.dt, D2.dt) && isequal(D1.update, D2.update)
end
Base.hash(D::Difference, u::UInt) = hash(D.dt, hash(D.t, xor(u, 0x055640d6d952f101)))
Base.hash(D::Difference, u::UInt) = hash(D.dt, hash(D.t, xor(u, 0x055640d6d952f101 % UInt)))
4 changes: 4 additions & 0 deletions test/Core/implicit_basis.jl
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Expand Up @@ -56,6 +56,10 @@ end
discrete_prob = DiscreteDataDrivenProblem(x)

d = Difference(get_iv(basis), dt = 1.0)
# On 32-bit builds (UInt == UInt32) the hash seed literal in Base.hash(::Difference, ::UInt)
# used to widen to UInt64 via `xor`, breaking SymbolicUtils hashconsing
# (https://github.com/SciML/DataDrivenDiffEq.jl/actions/runs/35188714123).
@test typeof(hash(d, UInt(1))) === UInt
@test Symbolics.symtype(d(first(states(basis)))) === Real
@test isempty(Symbolics.shape(d(first(states(basis)))))
∂ = Differential(get_iv(basis))
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