If you’re trying this out in the REPL, you might have stumbled on the fact
that list comprehensions currently aren’t type stable, unless you tell
Julia the type of the elements. So instead of Xinput =
[Array{Float64}(InnerArrayPts) for r in 1:OuterArrayPts] in your setup, do
Xinput
= Vector{Float64}[Array(Float64, InnerArrayPts) for r in 1:OuterArrayPts]
(I also switched which array constructor you use, but that shouldn’t matter
- it’s just a question of style, which is subjective :) ).
Note that Vector{Float64} is just a type alias for Array{Float64, 1}.
// T
On Tuesday, September 29, 2015 at 1:20:02 PM UTC+2, Alan Crawford wrote:
>
> I would like to preallocate memory of an array of arrays and pass it to a
> function to be filled in. I have created an example below that illustrates
> my question(s).
>
> Based on my (probably incorrect) understanding that it would be desirable
> to fix the type in my function, I would like to be able to pass my array of
> arrays, X, in a type stable way. However, I can't seem to pass
> Array{Array{Float64,N},1}. If, however, i do not attempt to impose the type
> on the function, it works.
>
> Is there a way to pass Array{Array{Float64,N},1 to my function? Do I even
> need to fix the type in the function to get good performance?
>
> # version of Julia: 0.4.0-rc3
>
> @generated function
> testfun1!{N}(X::Array{Array{Float64,1},1},Y::NTuple{N,Float64})
> quote
> for j in 1:$N, i in eachindex(X)
> X[i][j] = Y[j]
> end
> return X
> end
> end
>
> @generated function testfun2!{N}(X,Y::NTuple{N,Float64})
> quote
> for j in 1:$N, i in eachindex(X)
> X[i][j] = Y[j]
> end
> return X
> end
> end
>
> # Setup for function call
> InnerArrayPts = 3
> OuterArrayPts = 10
> Xinput = [Array{Float64}(InnerArrayPts) for r in 1:OuterArrayPts]
> Yinput = rand(InnerArrayPts)
>
> # Method Error Problem
> testfun1!(Xinput,tuple(Yinput...))
>
> # This works
> testfun2!(Xinput,tuple(Yinput...))
>
> I also tried with the following version of testfun1!() and again got a
> method error.
>
> @generated function
> testfun1!{N}(X::Array{Array{Float64,N},1},Y::NTuple{N,Float64})
> quote
> for j in 1:$N, i in eachindex(X)
> X[i][j] = Y[j]
> end
> return X
> end
> end
>
>
> I am sure i am misunderstanding something quite fundamental and/or missing
> something straightforward...
>
> Thanks,
> Alan
>
>
>
>
