For me, map is 100x slower:
julia> function f1(g,a)
[Pair(x,g) for x in a]
end
f1 (generic function with 1 method)
julia> function f2(g,a)
map(x->Pair(x,g), a)
end
f2 (generic function with 1 method)
julia> @time f1(2,ones(1_000_000));
25.158 milliseconds (28491 allocations: 24736 KB, 12.69% gc time)
julia> @time f1(2,ones(1_000_000));
6.866 milliseconds (8 allocations: 23438 KB, 37.10% gc time)
julia> @time f1(2,ones(1_000_000));
6.126 milliseconds (8 allocations: 23438 KB, 25.99% gc time)
julia> @time f2(2,ones(1_000_000));
684.994 milliseconds (2057 k allocations: 72842 KB, 1.72% gc time)
julia> @time f2(2,ones(1_000_000));
647.267 milliseconds (2000 k allocations: 70313 KB, 3.64% gc time)
julia> @time f2(2,ones(1_000_000));
633.149 milliseconds (2000 k allocations: 70313 KB, 0.91% gc time)
On Wednesday, June 17, 2015 at 12:04:52 PM UTC-4, Seth wrote:
>
> Sorry - it's part of a function:
>
> in_edges(g::AbstractGraph, v::Int) = [Edge(x,v) for x in badj(g,v)]
>
> vs
>
> in_edges(g::AbstractGraph, v::Int) = map(x->Edge(x,v), badj(g,v))
>
>
>
>
> On Wednesday, June 17, 2015 at 10:51:22 AM UTC-5, Mauro wrote:
>>
>> Note that inside a module is also global scope as each module has its
>> own global scope. Best move it into a function. M
>>
>> On Wed, 2015-06-17 at 17:22, Seth <[email protected]> wrote:
>> > The speedups are both via the REPL (global scope?) and inside a module.
>> I
>> > did a code_native on both - results are
>> > here: https://gist.github.com/sbromberger/b5656189bcece492ffd9.
>> >
>> >
>> >
>> > On Wednesday, June 17, 2015 at 9:56:22 AM UTC-5, Stefan Karpinski
>> wrote:
>> >>
>> >> I would have expected the comprehension to be faster. Is this in
>> global
>> >> scope? If so you may want to try the speed comparison again where each
>> of
>> >> these occur in a function body and only depend on function arguments.
>> >>
>> >> On Tue, Jun 16, 2015 at 10:12 AM, Seth <[email protected]
>> >> <javascript:>> wrote:
>> >>
>> >>> I have been using list comprehensions of the form
>> >>> bar(g, a) = [Pair(x, g) for x in a] and [foo(x) for x in a]
>> >>>
>> >>> but recently evaluated bar(g, a) = map(x->Pair(x, g),a) and
>> >>> map(x->foo(x),a)as substitutes.
>> >>>
>> >>> It seems from some limited testing that map is slightly faster than
>> the
>> >>> list comprehension, but it's on the order of 3-4% so it may just be
>> noise.
>> >>> Allocations and gc time are roughly equal (380M allocations,
>> ~27000MB, ~6%
>> >>> gc).
>> >>>
>> >>> Should I prefer one approach over the other (and if so, why)?
>> >>>
>> >>> Thanks!
>> >>>
>> >>
>> >>
>>
>>
