More reasonable default values of chunk size

Project.toml

@@ -1,6 +1,6 @@
 name = "AdvancedVI"
 uuid = "b5ca4192-6429-45e5-a2d9-87aec30a685c"
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 Bijectors = "76274a88-744f-5084-9051-94815aaf08c4"

src/AdvancedVI.jl

@@ -142,10 +142,13 @@ function grad!(
         - vo(alg, q(θ_), model, args...)
     end
 
-    chunk_size = getchunksize(typeof(alg))
     # Set chunk size and do ForwardMode.
-    chunk = ForwardDiff.Chunk(min(length(θ), chunk_size))
-    config = ForwardDiff.GradientConfig(f, θ, chunk)
+    chunk_size = getchunksize(typeof(alg))
+    config = if chunk_size == 0
+        ForwardDiff.GradientConfig(f, θ)
+    else
+        ForwardDiff.GradientConfig(f, θ, ForwardDiff.Chunk(length(θ), chunk_size))
+    end
     ForwardDiff.gradient!(out, f, θ, config)
 end
 

src/ad.jl

@@ -8,7 +8,6 @@ function setadbackend(::Val{:forward_diff})
     setadbackend(Val(:forwarddiff))
 end
 function setadbackend(::Val{:forwarddiff})
-    CHUNKSIZE[] == 0 && setchunksize(40)
     ADBACKEND[] = :forwarddiff
 end
 
@@ -26,13 +25,11 @@ function setadsafe(switch::Bool)
     ADSAFE[] = switch
 end
 
-const CHUNKSIZE = Ref(40) # default chunksize used by AD
+const CHUNKSIZE = Ref(0) # 0 means letting ForwardDiff set it automatically
 
 function setchunksize(chunk_size::Int)
-    if ~(CHUNKSIZE[] == chunk_size)
-        @info("[AdvancedVI]: AD chunk size is set as $chunk_size")
-        CHUNKSIZE[] = chunk_size
-    end
+    @info("[AdvancedVI]: AD chunk size is set as $chunk_size")
+    CHUNKSIZE[] = chunk_size
 end
 
 abstract type ADBackend end