> Can you comment on the performance implications of directly accessing
> fields vs your approach? I'm guessing that directly accessing the fields
> would be faster?
I think usually it should get inlined and there is no difference:
julia> immutable A
a::Int
end
julia> function f1(a::A,n)
out = 0
for i=1:n
out += a.a
end
end
f1 (generic function with 1 method)
julia> getA(a::A) = a.a
getA (generic function with 1 method)
julia> function f2(a::A,n)
out = 0
for i=1:n
out += getA(a)
end
end
f2 (generic function with 1 method)
julia> @code_native f1(A(5),10)
.text
Filename: none
Source line: 4
pushq %rbp
movq %rsp, %rbp
Source line: 4
popq %rbp
ret
julia> @code_native f2(A(5),10)
.text
Filename: none
Source line: 4
pushq %rbp
movq %rsp, %rbp
Source line: 4
popq %rbp
ret
>
>> On Wednesday, April 08, 2015 06:35:46 AM Kristoffer Carlsson wrote:
>> > I come from a Python background where direct access to fields in for
>> > example classes with the dot notation is very common.
>> >
>> > However, from what I have seen in different conversations, accessing
>> fields
>> > directly is not really Julian. Sort of a "fields are an implementation
>> > detail" mindset, and "what is important are the functions".
>> >
>> > Here is an example of a type hierarchy that is a little bit similar to
>> > types I am working with now:
>> >
>> > type Element
>> > vertices::Vector{Int}
>> > end
>> >
>> > type Node
>> > coordinates::Vector{Float64}
>> > id::Int
>> > end
>> >
>> > type FESection
>> > elements::Vector{Elements}
>> > nodes::Vector{Nodes}
>> > end
>> >
>> > type Mesh
>> > sections::Vector{FESection}
>> > end
>> >
>> > Now, let's say that I want to write a function to loop over all
>> vertices.
>> > One way (which I would do in Python is):
>> >
>> > mesh = Mesh(.....)
>> > for section in mesh.sections
>> > for element in section.elements
>> > for vertices in element.vertices
>> > blah bla
>> > end
>> > end
>> > end
>> >
>> >
>> >
>> > However, this accesses the fields directly. Would it be more Julian to
>> > write getters for the fields? Since Julia does not have @property like
>> > Python I realize that by accessing the fields you commit to exactly the
>> > name of the field and it's type while with a getter it would be more
>> > flexible.
>> >
>> > Best regards,
>> > Kristoffer Carlsson
>>
>>
