sampling from BetaSampler slower than directly from Beta

[adienes]

julia> _b = Beta(1, 20)
Beta{Float64}(α=1.0, β=20.0)

julia> _b2 = sampler(_b)
Distributions.BetaSampler{Float64, Exponential{Float64}, Distributions.GammaMTSampler{Float64}}(true, 1.0, 0.05, Exponential{Float64}(θ=1.0), Distributions.GammaMTSampler{Float64}(19.666666666666668, 0.07516460280028289, 19.666666666666668, 0.0331))

julia> @benchmark rand($rng, $_b)
BenchmarkTools.Trial: 10000 samples with 998 evaluations.
 Range (min … max):  18.119 ns … 53.231 ns  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):     19.747 ns              ┊ GC (median):    0.00%
 Time  (mean ± σ):   19.862 ns ±  1.154 ns  ┊ GC (mean ± σ):  0.00% ± 0.00%

          ▁ ▄▆█▄█▆▅▃                                           
  ▂▂▂▂▃▄▅▆██████████▇▇▅▄▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▂ ▃
  18.1 ns         Histogram: frequency by time          25 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.

julia> @benchmark rand($rng, $_b2)
BenchmarkTools.Trial: 10000 samples with 996 evaluations.
 Range (min … max):  21.754 ns … 79.401 ns  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):     28.448 ns              ┊ GC (median):    0.00%
 Time  (mean ± σ):   28.698 ns ±  1.924 ns  ┊ GC (mean ± σ):  0.00% ± 0.00%

                          ▁▃▆███▆▄▃▂▂                         ▂
  ▃▁▃▄▃▄▄▃▅▅▄▄▃▃▃▄▄▄▄▄▁▃▃▄████████████▇▇▇██▇▇▆▆▅▅▆▅▅▆▄▅▄▄▅▅▆▅ █
  21.8 ns      Histogram: log(frequency) by time      35.6 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.```



julia> versioninfo()
Julia Version 1.10.0
Commit 3120989f39b (2023-12-25 18:01 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 10 × Apple M1 Max
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, apple-m1)
  Threads: 1 on 8 virtual cores


Distributions v0.25.107

[adienes]

not sure how I got this but I think I was reading the wrong thing