On Wednesday, June 4, 2014 11:49:54 PM UTC+2, Ivar Nesje wrote:
> It does not look like jl_array_del_end currently frees any memory
>
>
> https://github.com/JuliaLang/julia/blob/0dacb65c0587eab268362c4dece1b2c662bef15e/src/array.c#L616
>
Ah, OK.
> I think you could gain something by storing pointers or object ids
> directly in a typed array, and avoid the safety features and garbage
> collector traverses that reduces performance.
>
Well, I would have thought so, too, but somehow it doesn't look that way?
For example, consider the following code (inside a function):
a = Array(Uint, n)
resize!(a, 0)
for i = 1:n
push!(a, i)
end
I would have thought it would be faster than if you replace Uint with Any –
but it actually seems to be quite a bit slower, for some reason. Let's add
a simple type (omitting the field type declaration on purpose, to create
some overhead):
type Entry
val
end
Now, the following code is a tad slower than pushing ints onto an Any
array, but still faster than pushing them onto an Uint array:
a = Array(Any, n)
resize!(a, 0)
for i = 1:n
push!(a, Entry(i))
end
The reason I used Uint and not Int was that I intended to use object_id().
If I push the ints directly onto an Int array, things are *almost* as fast
as pushing onto an Any array, but still not quite as fast, oddly enough.
(And pushing object_id(Entry(i)) isn't all that fast.)
>From my rather informal and unsystematic benchmarking, it actually seems
that using a cell array with push! is rather efficient. (But maybe I'm
doing things wrong…)
