Add docs page for subpackages

docs/pages.jl

@@ -6,6 +6,7 @@ pages = [
     "AbstractVectorOfArrayInterface.md",
     "array_types.md",
     "ragged_arrays.md",
+    "subpackages.md",
     "plotting.md",
     "recursive_array_functions.md",
 ]

docs/src/subpackages.md

@@ -0,0 +1,102 @@
+# Subpackages
+
+RecursiveArrayTools.jl ships several optional subpackages under `lib/`. Each is a
+separate Julia package that adds functionality which was split out of the main
+package to avoid method invalidations that would increase load times for users who
+don't need that functionality.
+
+## RecursiveArrayToolsRaggedArrays
+
+True ragged (non-rectangular) array types that preserve exact structure without
+zero-padding. See the [Ragged Arrays](@ref) page for full documentation.
+
+```julia
+using RecursiveArrayToolsRaggedArrays
+```
+
+## RecursiveArrayToolsShorthandConstructors
+
+Shorthand `VA[...]` and `AP[...]` constructor syntax for `VectorOfArray` and
+`ArrayPartition`.
+
+This is separated from the main package because the `getindex(::Type, ...)` method
+definitions invalidate compiled specializations of `Base.getindex(::Type{T}, vals...)`
+from Base, increasing load times for downstream packages that don't need the syntax.
+
+```julia
+using RecursiveArrayToolsShorthandConstructors
+```
+
+### Usage
+
+```julia
+using RecursiveArrayTools
+using RecursiveArrayToolsShorthandConstructors
+
+# VectorOfArray shorthand (equivalent to VectorOfArray([[1,2,3], [4,5,6]]))
+u = VA[[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+
+# ArrayPartition shorthand (equivalent to ArrayPartition(x0, v0, a0))
+x0, v0, a0 = rand(3, 3), rand(3, 3), rand(3, 3)
+u0 = AP[x0, v0, a0]
+u0.x[1] === x0  # true
+
+# Nesting works
+nested = VA[fill(1, 2, 3), VA[3ones(3), zeros(3)]]
+```
+
+Without this package, use the equivalent explicit constructors:
+
+```julia
+u = VectorOfArray([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
+u0 = ArrayPartition(x0, v0, a0)
+```
+
+## RecursiveArrayToolsArrayPartitionAnyAll
+
+Optimized `any` and `all` for `ArrayPartition` that iterate partition-by-partition
+instead of element-by-element, giving ~1.5-1.8x speedup on full scans.
+
+This is separated from the main package because `any(f::Function, ::ArrayPartition)`
+invalidates ~780 compiled specializations of `any(f::Function, ::AbstractArray)`.
+
+```julia
+using RecursiveArrayToolsArrayPartitionAnyAll
+```
+
+### Usage
+
+```julia
+using RecursiveArrayTools
+using RecursiveArrayToolsArrayPartitionAnyAll
+
+ap = ArrayPartition(rand(1000), rand(1000), rand(1000))
+
+# These now use the optimized partition-by-partition iteration
+any(isnan, ap)       # ~1.5x faster than default
+all(x -> x > 0, ap)  # ~1.8x faster than default
+```
+
+Without this package, `any`/`all` use the default `AbstractArray` implementation
+which is correct but slower due to per-element partition indexing overhead.
+
+### Why is it faster?
+
+`ArrayPartition` stores data as a tuple of arrays. The default `AbstractArray`
+`any`/`all` iterates element-by-element, which requires computing which partition
+each linear index falls into. The optimized methods iterate over each partition
+array directly, avoiding that lookup overhead entirely.
+
+## Installation
+
+All subpackages can be installed from the monorepo:
+
+```julia
+using Pkg
+Pkg.add(url = "https://github.com/SciML/RecursiveArrayTools.jl",
+        subdir = "lib/RecursiveArrayToolsRaggedArrays")
+Pkg.add(url = "https://github.com/SciML/RecursiveArrayTools.jl",
+        subdir = "lib/RecursiveArrayToolsShorthandConstructors")
+Pkg.add(url = "https://github.com/SciML/RecursiveArrayTools.jl",
+        subdir = "lib/RecursiveArrayToolsArrayPartitionAnyAll")
+```