`rand(Float32, n)` generates two values of the same number over and over when n is < 16

[KristofferC]

julia> rand(Float32, 8)
8-element Vector{Float32}:
 0.20123601
 0.20123601
 0.20944309
 0.20944309
 0.22612727
 0.22612727
 0.67038965
 0.67038965

[AayushSabharwal]

This might be a platform-specific issue?

julia> rand(Float32, 2, 2)
2×2 Matrix{Float32}:
 0.0428355  0.923347
 0.23499    0.743639

julia> rand(Float32, 2, 2)
2×2 Matrix{Float32}:
 0.273889  0.0762916
 0.887567  0.86231

julia> rand(Float32, 2, 2)
2×2 Matrix{Float32}:
 0.444505  0.0416906
 0.641743  0.096535

julia> versioninfo()
Julia Version 1.11.3
Commit d63adeda50d (2025-01-21 19:42 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 8 × Apple M2
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m2)
Threads: 16 default, 2 interactive, 4 GC (on 4 virtual cores)
Environment:
  JULIA_PKG_USE_CLI_GIT = true
  JULIA_PKG_SERVER = https://internal.juliahub.com

[KristofferC]

The regression is not present in 1.11.

[AayushSabharwal]

I see, thanks for the clarification.

[KristofferC]

Bisected to d09abe5, #56144, cc @giordano.

This should basically be a non-functional change

Famous last workds.

[giordano]

julia/stdlib/Random/src/XoshiroSimd.jl

Line 49 in cba19bf

l = _uint2float(ui, Float32)

this line does look fishy. The rest of the change was good though 😁