Incidentally, this errors in 0.5 (but works fine in 0.4)
julia> s=0.0;
julia> m=rand(10000,1000);
julia> @time for el in m
s = s + el
end
ERROR: UndefVarError: s not defined
[inlined code] from .\none:2
in anonymous at .\no file:4294967295
in eval at <invalid>:0
quinta-feira, 25 de Fevereiro de 2016 às 13:35:56 UTC, abc escreveu:
>
> For the following matrix
> my_matrix = randn(10000, 1000)
> using eachindex to access all elements is much slower than using ranges
> or even for el in my_matrix, even though it says in the documentation (
> http://docs.julialang.org/en/release-0.4/stdlib/arrays/#Base.eachindex)
> that eachindex uses ranges for Arrays.
>
> Some code and numbers:
> julia> sum = 0.0
> julia> @time for iter in eachindex(my_matrix)
> sum += my_matrix[iter]
> end
> 1.288944 seconds (50.00 M allocations: 915.519 MB, 3.36% gc time)
> julia> sum = 0.0
> julia> @time for i in 1:10000, j in 1:1000
> sum += my_matrix[i,j]
> end
> 0.681678 seconds (34.38 M allocations: 524.582 MB, 2.45% gc time)
> julia> sum = 0.0
> julia> @time for el in my_matrix
> sum += el
> end
> 1.063564 seconds (40.00 M allocations: 762.993 MB, 3.41% gc time)
>
> Am I reading the documentation wrong, or is there something strange with
> the matrix indexing? Because as it is, I don't see any benefit of using
> anything different than simple ranges for manipulating matrices.
>
