> Thanks Mauro - really useful to know. So it seems that in this
> particular instance the number of nested loops does change with N, so
> I think the code would fall into the latter case.
Sorry, I wasn't clear: no, only the number of iterations would change.
With numbers of nested loops I meant, say two:
for i=1:n
for j=1:m
...
end
end
to three
for i=1:n
for j=1:m
for k=1:l
...
end
end
end
which could be done with a generated function (look for Base.Cartesian).
>> Well, it is always hard to tell what's best. If you need certainty,
>> then you need to benchmark. Note that in below example, Julia will
>> compile a specialized version of the function for each NTuple anyway.
>> This may be good or bad, depending on how much time compilation vs
>> running takes.
And above was also not clear, I should have written:
"Note that in MY example below, Julia will compile a specialized version
of the function for each NTuple with a different N anyway."
>> A case for a generated function would be if, say, the number of nested
>> loops would change depending on some parameter, say the dimensionality
>> of an array.
>>
>>> Thanks, Alan
>>>
>>>
>>> was just an illustration of a the larger piece of code where I am making
>>> using
>>> On 29 Sep 2015, at 13:48, Mauro <mauro...@runbox.com> wrote:
>>>
>>>> I don't think that you need nor that you should use generated functions.
>>>> But maybe I'm wrong, what are you trying to achieve? This should work
>>>> as you want:
>>>>
>>>> function testfun2!{N}(X,Y::NTuple{N,Float64})
>>>> for i in eachindex(X), j in 1:N # much better to have the loop this way
>>>> X[i][j] = Y[j]
>>>> end
>>>> return X
>>>> end
>>>>
>>>> # Setup for function call
>>>> InnerArrayPts = 3
>>>> OuterArrayPts = 10
>>>> Xinput = [Array{Float64}(InnerArrayPts) for r in 1:OuterArrayPts]
>>>> Yinput = rand(InnerArrayPts)
>>>>
>>>> testfun2!(Xinput,tuple(Yinput...))
>>>>
>>>> On Tue, 2015-09-29 at 13:20, Alan Crawford <a.r.crawf...@gmail.com> 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
