This has been one year in the making, but the first release of FixedSizeArrays.jl is finally out and you can install it in your environment with import Pkg Pkg.add("FixedSizeArrays") This package can be installed in Julia v1.10 and following releases, but the improvements mentioned in the sections…

was special-cased in the compiler to be (effectively?) immutable. This isn’t quite true. IIUC the actual “size” field was known by the compiler not to change, but the backing was still mutable (preventing optimization). Also as of 1.11, the compiler dropped this optimization since Array is just a…

[image] mikmoore: At some point I thought I learned that Array{T, D} for D != 1 was special-cased in the compiler to be (effectively?) immutable. But if this package has utility for D other than 1, then it must be that said special-casing only covers part of the surface area. julia> using Fix…

Cthulhu tells me there was a type instability in my code unrelated to FArray. Once I fixed that both the number of allocations and the total amount of allocated memory go up with FArray w.r.t plain Array =(

I’ve added MutableSmallVector to my benchmarks above. I think that FixedSizeArrays is a great package, and that the title of this thread sounds exactly right. However, looking at the benchmarks (which do not cover all sizes and element types!), I’m asking myself where, say, FixedSizeVector really s…

In my mind the main competitor of FixedSizeArray is only Base.Array, in the role of a general purpose container. Specialised containers like MArray are different beasts: they can be useful when you want to do something smart in very specific cases (e.g. dispatching on the size, or when you know you …

How does this compare with SizedArrays from StaticArrays.jl? IIRC SizedArrays are also backed by normal memory and the only notable difference I can see is that the size information is stored as value instead of type parameter.

Besides the size being a type parameter versus an instance value, SizedArray wraps any AbstractArray, while FixedSizeArray is a DenseArray that wraps a DenseVector (default to Memory). For example, SizedArray can wrap a StepRange, but a FixedSizeArray can’t (but the constructor may copy the element…

I think the issue that this package is addressing is fundamentally the following: julia> foo()=Base.llvmcall("""call void asm ";", "~{memory}"() ret void""", Tuple{} , Nothing) julia> function bar(x) @inbounds a=x[1] foo() @inbounds b=x[1] a+b end julia> …

Is it possible to use the e.g. 64-byte aligned memory provided by AlignedAllocs.jl as the memory for a FixedSizeVector?

The memory backend can be any DenseVector: src/FixedSizeArray.jl 35fb27aac struct FixedSizeArray{T,N,Mem<:DenseVector{T}} <: DenseArray{T,N} mem::Mem

[ANN] FixedSizeArrays.jl: What Array probably should have been

Package Announcements

JeffreySarnoff June 14, 2025, 5:39pm 74

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Topic		Replies	Views
FixedSizeVectors with cache-aligned memory? General Usage array , arrays	18	754	June 19, 2025
Memory allocations when returning vectors General Usage array , memory-allocation	15	1569	June 6, 2018
Strange performance of a loop Performance	37	3416	July 21, 2018
Increase in allocations with Julia v1.11-beta Internals & Design performance , arrays	46	3395	May 8, 2024
Small Vectors Data	19	2026	November 13, 2024

[ANN] FixedSizeArrays.jl: What Array probably should have been

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