M1 = rand(7,3)
M = view(M1,1:6,1:3) # some memory allocation occurs here
a= rand(3)
c1 = zeros(6)
c =view(c1) # some memory allocation occurs here
I don't think that either the M or c line allocates anything (on the heap).
ArrayViews are immutables, so they are stack allocated (as far as I can
understand) and virtually cost-free.
On Saturday, February 6, 2016 at 6:35:34 PM UTC-5, Nitin Arora wrote:
>
> I see, thanks for the information. I think, if possible, this feature will
> help the language a lot.
>
> I have recommended Julia to many of my colleagues (they all love it over
> Fortran and Matlab) and most of them seem to run into this issue. I think,
> a modern language with soo much elegance and potential, like Julia, should
> nail such major issues. I am sure by V-1.0 we will have the best scientific
> programming language ever :-)
>
> thanks,
> Nitin
>
> On Saturday, February 6, 2016 at 3:55:56 AM UTC-8, Tim Holy wrote:
>>
>> On Friday, February 05, 2016 05:24:04 PM Nitin Arora wrote:
>> > Thanks Tim, this is very useful. I will probably use CartesianRange
>> now.
>> >
>> > Is Julia 0.5 Arraypocalypse planning to address this issue as well ?
>>
>> I don't think there's a way to solve this by changing our implementation
>> of
>> views; I think it's more of a compiler issue, and the fact that
>>
>> julia> isbits(CartesianRange((3,5)))
>> true
>>
>> julia> immutable ArrayWrapper{M}
>> data::M
>> end
>>
>> julia> z = rand(5,5);
>>
>> julia> isbits(ArrayWrapper(z))
>> false
>>
>>
>> Since I don't work on the compiler, I can't speak for what's going to
>> happen
>> there, but I'd be surprised if this changes in 0.5.
>>
>> Best,
>> --Tim
>>
>> >
>> > thanks,
>> > Nitin
>> >
>> > On Friday, February 5, 2016 at 3:24:34 PM UTC-8, Tim Holy wrote:
>> > > On Friday, February 05, 2016 08:17:21 AM Kevin Squire wrote:
>> > > > I think this needs to be @time bar(A).
>> > >
>> > > Yeah, sorry for the typo.
>> > >
>> > > > I get
>> > > >
>> > > > julia> @time bar(A)
>> > > >
>> > > > 0.000269 seconds (5 allocations: 176 bytes)
>> > > >
>> > > > 20010.937886591404
>> > >
>> > > That's just REPL allocation. Since A has 10000 columns, if this
>> strategy
>> > > were
>> > > allocating you'd expect "10000+n allocations," where n comes from the
>> > > REPL.
>> > >
>> > > --Tim
>>
>>
