Switch default storage to MemoryRef-based array

docs/src/usage.md

@@ -24,12 +24,12 @@ julia> arr = [10 20; 30 14]
  30  14
 
 julia> FixedSizeArray(arr)  # construct from an `AbstractArray` value
-2×2 FixedSizeArray{Int64, 2, Memory{Int64}}:
+2×2 FixedSizeArray{Int64, 2, FixedSizeArrays.UnsafeRefArray{Int64}}:
  10  20
  30  14
 
 julia> FixedSizeArray{Float64}(arr)  # construct from an `AbstractArray` value while converting element type
-2×2 FixedSizeArray{Float64, 2, Memory{Float64}}:
+2×2 FixedSizeArray{Float64, 2, FixedSizeArrays.UnsafeRefArray{Float64}}:
  10.0  20.0
  30.0  14.0
 ```
@@ -45,7 +45,7 @@ julia> arr = transpose([10 20; 30 14])
  20  14
 
 julia> adapt(FixedSizeArray, arr)
-2×2 transpose(::FixedSizeArray{Int64, 2, Memory{Int64}}) with eltype Int64:
+2×2 transpose(::FixedSizeArray{Int64, 2, FixedSizeArrays.UnsafeRefArray{Int64}}) with eltype Int64:
  10  30
  20  14
 ```
@@ -68,7 +68,7 @@ The `FixedSizeArray{T,N,Mem}` type has three parameters:
 
 !!! note "Implementation details"
 
-    In Julia v1.11+, the default memory backend is the [`Memory{T}`](https://docs.julialang.org/en/v1/base/arrays/#Core.Memory) type.
+    In Julia v1.11+, the default memory backend is `UnsafeRefArray{T}`, an internal type that wraps a `MemoryRef{T}`. This allows the pointer to be inlined into the `FixedSizeArray` struct, saving a memory indirection compared to `Memory{T}`.
     Since Julia v1.10 does not have the `Memory` type, to make this package usable also on Julia v1.10 `Vector{T}` is used as memory backend, but many of the memory/performance optimizations enabled by this package will not be available in that version of Julia and in general `FixedSizeArrays.jl` does not provide significant improvements compared to `Base`'s `Array` for that specific version.
 
 To make it easier to refer to the concrete type `FixedSizeArray{T,N,Mem}` with the default memory backend, the following convenient aliases are available:
@@ -88,17 +88,17 @@ julia> iter = (i for i ∈ 7:9 if i≠8);
 julia> using FixedSizeArrays, Collects
 
 julia> collect_as(FixedSizeArray, iter)  # construct from an arbitrary iterator
-2-element FixedSizeArray{Int64, 1, Memory{Int64}}:
+2-element FixedSizeArray{Int64, 1, FixedSizeArrays.UnsafeRefArray{Int64}}:
  7
  9
 
 julia> collect_as(FixedSizeArray{Float64}, iter)  # construct from an arbitrary iterator while converting element type
-2-element FixedSizeArray{Float64, 1, Memory{Float64}}:
+2-element FixedSizeArray{Float64, 1, FixedSizeArrays.UnsafeRefArray{Float64}}:
  7.0
  9.0
 
 julia> collect_as(FixedSizeVectorDefault, (3.14, -4.2, 2.68))  # construct from a tuple
-3-element FixedSizeArray{Float64, 1, Memory{Float64}}:
+3-element FixedSizeArray{Float64, 1, FixedSizeArrays.UnsafeRefArray{Float64}}:
   3.14
  -4.2
   2.68

ext/FixedSizeArraysRandomExt.jl

@@ -21,4 +21,20 @@ if VERSION < v"1.11"
     end
 end
 
+# UnsafeRefArray-backed: delegate rand! to the underlying Memory so that the
+# specialized SIMD path in Random.XoshiroSimd is hit.
+if @isdefined Memory
+    using FixedSizeArrays: UnsafeRefArray
+
+    function Random.rand!(rng::Random.AbstractRNG, A::UnsafeRefArray{T}, sp::Random.Sampler) where {T}
+        Random.rand!(rng, parent(A), sp)
+        return A
+    end
+
+    function Random.rand!(r::Random.MersenneTwister, A::UnsafeRefArray{Float64}, I::Random.SamplerTrivial{<:Random.FloatInterval{Float64}})
+        Random.rand!(r, parent(A), I)
+        return A
+    end
+end
+
 end # module FixedSizeArraysRandomExt

src/FixedSizeArray.jl

@@ -253,6 +253,12 @@ function with_stripped_type_parameters_unchecked(::TypeParametersElementType, ::
     s = GenericMemory{K, T, AS} where {T}
     Val{s}()
 end
+if (@isdefined UnsafeRefArray)
+    function with_stripped_type_parameters_unchecked(::TypeParametersElementType, ::Type{<:UnsafeRefArray})
+        s = UnsafeRefArray
+        Val{s}()
+    end
+end
 
 # `Base.@assume_effects :consistent` is a workaround for:
 # https://github.com/JuliaLang/julia/issues/56966
@@ -418,22 +424,22 @@ end
     FixedSizeArrayDefault{T,N}(undef, size1::Int, size2::Int, ...)
     FixedSizeArrayDefault{T,N}(array::AbstractArray)
 
-Construct a [`FixedSizeArray`](@ref) with element type `T`, number of dimensions `N`, and the default memory backend (`Vector{T}` on Julia v1.10, `Memory{T}` on Julia v1.11+).
+Construct a [`FixedSizeArray`](@ref) with element type `T`, number of dimensions `N`, and the default memory backend (`Vector{T}` on Julia v1.10, `UnsafeRefArray{T}` on Julia v1.11+).
 """
 const FixedSizeArrayDefault = FixedSizeArray{T, N, default_underlying_storage_type{T}} where {T, N}
 """
     FixedSizeVectorDefault{T}(undef, size::NTuple{1,Int})
     FixedSizeVectorDefault{T}(undef, size1::Int)
     FixedSizeVectorDefault{T}(array::AbstractVector)
 
-Construct a [`FixedSizeVector`](@ref) with element type `T`, and the default memory backend (`Vector{T}` on Julia v1.10, `Memory{T}` on Julia v1.11+).
+Construct a [`FixedSizeVector`](@ref) with element type `T`, and the default memory backend (`Vector{T}` on Julia v1.10, `UnsafeRefArray{T}` on Julia v1.11+).
 """
 const FixedSizeVectorDefault = FixedSizeArrayDefault{T, 1} where {T}
 """
     FixedSizeMatrixDefault{T}(undef, size::NTuple{2,Int})
     FixedSizeMatrixDefault{T}(undef, size1::Int, size2::Int)
     FixedSizeMatrixDefault{T}(array::AbstractMatrix)
 
-Construct a [`FixedSizeMatrix`](@ref) with element type `T`, and the default memory backend (`Vector{T}` on Julia v1.10, `Memory{T}` on Julia v1.11+).
+Construct a [`FixedSizeMatrix`](@ref) with element type `T`, and the default memory backend (`Vector{T}` on Julia v1.10, `UnsafeRefArray{T}` on Julia v1.11+).
 """
 const FixedSizeMatrixDefault = FixedSizeArrayDefault{T, 2} where {T}

src/FixedSizeArrays.jl

@@ -5,11 +5,15 @@ using Collects: Collect, collect_as
 using LightBoundsErrors: checkbounds_lightboundserror
 using LightBoundsErrors: LightBoundsError as BoundsErrorLight
 
-const default_underlying_storage_type = (@isdefined Memory) ? Memory : Vector
+if (@isdefined Memory)
+    include("refarray.jl")
+end
+
+const default_underlying_storage_type = (@isdefined Memory) ? UnsafeRefArray : Vector
 
-const optional_memory = (@isdefined Memory) ? (Memory,) : ()
+const optional_memory = (@isdefined Memory) ? (UnsafeRefArray,) : ()
 const optional_atomic_memory = (@isdefined AtomicMemory) ? (AtomicMemory,) : ()
-const optional_generic_memory = (@isdefined GenericMemory) ? (GenericMemory,) : ()
+const optional_generic_memory = (@isdefined GenericMemory) ? (UnsafeRefArray,) : ()
 
 include("FixedSizeArray.jl")
 

src/refarray.jl

@@ -0,0 +1,102 @@
+# Internal type used as the default, heap-backed parent container for FixedSizeArray.
+# This is used over Memory{T}, because a MemoryRef inlines into the parent struct, and
+# contains the pointer. This way, it saves a memory indirection over Memory.
+# This type does not boundscheck, hence the unsafety. The FSA wrapper will handle boundschecks.
+struct UnsafeRefArray{T} <: DenseVector{T}
+    ref::MemoryRef{T}
+end
+
+# TODO: Would be nice to be able to omit the check for n < 0 in the Memory
+# constructor, but this is in the memorynew built-in and cannot be disabled
+function UnsafeRefArray{T}(::UndefInitializer, n::Int) where T
+    mem = Memory{T}(undef, n)
+    UnsafeRefArray{T}(memoryref(mem))
+end
+
+UnsafeRefArray{T}(::UndefInitializer, n::Tuple{Int}) where T = UnsafeRefArray{T}(undef, @inbounds(n[1]))
+
+@static if VERSION < v"1.12.0-DEV.966"
+    Base.parent(x::UnsafeRefArray) = x.ref.mem
+else
+    Base.parent(x::UnsafeRefArray) = parent(x.ref)
+end
+
+# This version introduced Base.memoryindex as public API
+@static if VERSION < v"1.13.0-DEV.1289"
+    internal_memindex(x::MemoryRef) = Core.memoryrefoffset(x)
+else
+    internal_memindex(x::MemoryRef) = Base.memoryindex(x)
+end
+
+function Base.checkbounds(A::UnsafeRefArray, is...)
+    checkbounds_lightboundserror(A, is...)
+end
+
+Base.size(x::UnsafeRefArray) = ((length(parent(x)) - internal_memindex(x.ref) + 1),)
+
+Base.firstindex(::UnsafeRefArray) = 1
+
+function Base.getindex(x::UnsafeRefArray, i::Int)
+    @inbounds(memoryref(x.ref, i)[])
+end
+
+function Base.setindex!(x::UnsafeRefArray{T}, v, i::Int) where T
+    vT = convert(T, v)::T
+    @inbounds(memoryref(x.ref, i)[] = vT)
+end
+
+Base.IndexStyle(::Type{<:UnsafeRefArray}) = Base.IndexLinear()
+
+Base.elsize(::Type{UnsafeRefArray{T}}) where {T} = Base.elsize(Memory{T})
+
+function Base.similar(A::UnsafeRefArray, ::Type{S}, dims::Dims) where S
+    UnsafeRefArray{S}(undef, dims)
+end
+
+function Base.isassigned(x::UnsafeRefArray, i::Int)
+    @boundscheck checkbounds(Bool, x, i) || false
+    ref = @inbounds memoryref(x.ref, i)
+    isassigned(ref)
+end
+
+function Base.copy(x::UnsafeRefArray)
+    len = length(x)
+    newmem = Memory{eltype(x)}(undef, len)
+    newref = memoryref(newmem)
+    @inbounds unsafe_copyto!(newref, x.ref, len)
+    typeof(x)(newref)
+end
+
+function Base.unsafe_convert(::Type{Ptr{T}}, x::UnsafeRefArray) where T
+    Base.unsafe_convert(Ptr{T}, x.ref)
+end
+
+Base.dataids(x::UnsafeRefArray) = Base.dataids(parent(x))
+
+# Collects.jl interface for UnsafeRefArray
+
+function (c::Collect)(::Type{UnsafeRefArray{T}}, collection) where {T}
+    if collection isa UnsafeRefArray{T}
+        return copy(collection)
+    end
+    if (T isa Type) && Base.IteratorSize(collection) isa Union{Base.HasLength, Base.HasShape}
+        result = UnsafeRefArray{T}(undef, Int(length(collection))::Int)
+        copyto!(result, collection)
+        return result
+    end
+    vec = c(Vector{T}, collection)
+    result = UnsafeRefArray{T}(undef, length(vec))
+    copyto!(result, vec)
+    result
+end
+
+function (c::Collect)(::Type{UnsafeRefArray}, collection)
+    if collection isa UnsafeRefArray
+        return copy(collection)
+    end
+    vec = c(Vector, collection)
+    T = eltype(vec)
+    result = UnsafeRefArray{T}(undef, length(vec))
+    copyto!(result, vec)
+    result
+end

test/runtests.jl

@@ -2,6 +2,9 @@ using Test
 using LinearAlgebra, Adapt
 using FixedSizeArrays
 using FixedSizeArrays: checked_dims
+if @isdefined Memory
+    using FixedSizeArrays: UnsafeRefArray
+end
 using Collects: collect_as
 using OffsetArrays: OffsetArray
 using Random: Random
@@ -137,7 +140,7 @@ end
 
     @testset "default underlying storage type" begin
         default = FixedSizeArrays.default_underlying_storage_type
-        @test default === (@isdefined(Memory) ? Memory : Vector)
+        @test default === (@isdefined(Memory) ? UnsafeRefArray : Vector)
         return_type = FixedSizeVector{Int,default{Int}}
         @test return_type === FixedSizeVectorDefault{Int}
         test_inferred(FixedSizeArray{Int}, return_type, (undef, 3))
@@ -155,6 +158,31 @@ end
         test_inferred(FixedSizeVector{Int}, return_type, arr)
     end
 
+    (@isdefined Memory) && @testset "UnsafeRefArray" begin
+        @testset "tuple undef constructor" begin
+            a = UnsafeRefArray{Int}(undef, (5,))
+            @test length(a) == 5
+        end
+        @testset "similar" begin
+            a = UnsafeRefArray{Int}(undef, 3)
+            b = similar(a, Float64, (4,))
+            @test b isa UnsafeRefArray{Float64}
+            @test length(b) == 4
+        end
+        @testset "collect_as identity" begin
+            a = UnsafeRefArray{Int}(undef, 3)
+            a[1] = 1; a[2] = 2; a[3] = 3
+            b = collect_as(UnsafeRefArray{Int}, a)
+            @test b isa UnsafeRefArray{Int}
+            @test b !== a
+            @test b[1] == 1 && b[2] == 2 && b[3] == 3
+            c = collect_as(UnsafeRefArray, a)
+            @test c isa UnsafeRefArray{Int}
+            @test c !== a
+            @test c[1] == 1 && c[2] == 2 && c[3] == 3
+        end
+    end
+
     @testset "`undef` construction without element type" begin
         @test_throws MethodError FixedSizeVector(undef, 1)
         @test_throws MethodError FixedSizeMatrix(undef, 1, 1)
@@ -223,7 +251,7 @@ end
     end
 
     @testset verbose=true "test sets for multiple supported storage types" begin
-        for storage_type ∈ (((@isdefined Memory) ? (Memory,) : ())..., Vector)
+        for storage_type ∈ (((@isdefined Memory) ? (UnsafeRefArray,) : ())..., Vector)
             FSV = fsv(storage_type)
             FSM = fsm(storage_type)
             FSA = fsa(storage_type)
@@ -549,7 +577,7 @@ end
                     (FSV, FSV),
                     (
                         if @isdefined Memory
-                            ((FSV, Memory), (Memory, FSV))
+                            ((FSV, UnsafeRefArray), (UnsafeRefArray, FSV))
                         else
                             ()
                         end