Performance of resize! vs pre-allocating with zeros(...)

[Sukera]

@fcdimitr

One strategy is lazy allocation, the other is eager. In the lazy case, the pages are not allocated by the OS until needed, hence the penalty when visiting them for the first time.

Please refer to the following thread for an in-depth discussion about the (dis-)advantages of using calloc, as well as links to further discussions.

Faster zeros with calloc

Abstract TL; DR zeros_via_calloc is a potentially faster version of zeros that is comparable to Array{T}(undef, ...) and numpy.zeros. function zeros_via_calloc(::Type{T}, dims::Integer...) where T ptr = Ptr{T}(Libc.calloc(prod(dims), sizeof(T))) return unsafe_wrap(Array{T}, ptr, dims; own=true) end # Windows benchmark julia> @btime zeros_via_calloc(Float64, 1024, 1024); 12.400 μs (2 allocations: 8.00 MiB) julia> @btime zeros(Float64, 1024, 1024); 1.652 ms (2 allocations: 8.00 MiB)…