Use the inner Product constructor in arraydist

HISTORY.md

@@ -1,3 +1,9 @@
+# 0.42.4
+
+`arraydist` on a vector of univariate distributions now builds its `Distributions.Product` through the inner constructor instead of `Product(dists)`, which is deprecated. The outer constructor calls `Base.depwarn`, and that walks a backtrace on every call, so models with an `arraydist` likelihood paid it once per evaluation. The return type is unchanged.
+
+This restores the behaviour of the DistributionsAD implementation, which used the inner constructor for the same reason before `arraydist` moved here in 0.40.4.
+
 # 0.42.3
 
 Worked around an upstream Julia code-generation bug that, under concurrent allocation load, could crash the model re-evaluation performed by `ParamsWithStats`. The affected re-evaluation is now routed through an internal function barrier that avoids the miscompilation; behaviour is unchanged. The crash was originally reported in [AbstractMCMC.jl#214](https://github.com/TuringLang/AbstractMCMC.jl/issues/214).

Project.toml

@@ -1,6 +1,6 @@
 name = "DynamicPPL"
 uuid = "366bfd00-2699-11ea-058f-f148b4cae6d8"
-version = "0.42.3"
+version = "0.42.4"
 
 [deps]
 ADTypes = "47edcb42-4c32-4615-8424-f2b9edc5f35b"

src/distribution_wrappers.jl

@@ -129,5 +129,10 @@ function arraydist(dists::AbstractArray{<:Distribution})
     return product_distribution(dists)
 end
 function arraydist(dists::AbstractVector{<:UnivariateDistribution})
-    return Product(dists)
+    # The inner constructor skips `Product`'s deprecation warning, which `Base.depwarn`
+    # makes expensive because it walks a backtrace on every call.
+    V = typeof(dists)
+    T = eltype(dists)
+    S = Distributions.value_support(T)
+    return Product{S,T,V}(dists)
 end

test/distribution_wrappers.jl

@@ -5,9 +5,10 @@ using Dates: now
 __now__ = now()
 
 using DynamicPPL: DynamicPPL, @model
-using Test: @testset, @test
-using Distributions: Normal, logpdf
+using Test: @testset, @test, @test_logs
+using Distributions: Normal, Product, logpdf, product_distribution
 using Bijectors: Bijectors
+using StableRNGs: StableRNG
 
 @testset "distribution_wrappers.jl" begin
     d = Normal()
@@ -23,6 +24,17 @@ using Bijectors: Bijectors
     @test Bijectors.logpdf_with_trans(nd, 30, true) == 0
 end
 
+@testset "arraydist on a vector of univariates" begin
+    rng = StableRNG(468)
+    dists = Normal.(randn(rng, 3))
+    x = randn(rng, 3)
+    # `Product(v)` calls `Base.depwarn`, which walks a backtrace on every call, so this has
+    # to go through the inner constructor instead.
+    @test_logs DynamicPPL.arraydist(dists)
+    @test DynamicPPL.arraydist(dists) isa Product
+    @test logpdf(DynamicPPL.arraydist(dists), x) == logpdf(product_distribution(dists), x)
+end
+
 @info "Completed $(@__FILE__) in $(now() - __now__)."
 
 end # module