[Jprogramming] strategies for building long lists of boxes

[Joe Bogner]

Is this an example of what you're referring to?

bld2=: 3 : 0
(<'.') 4 : 'y , x'  ^:y   ''
)

   ts 'l=:bld2 1e2'
0.00177792 6400
 ts 'l=:bld2 1e3'
0.0850437 20544
   ts 'l=:bld2 1e4'
8.28457 217152

$ l
10000

Looping explicitly is similar

bld4 =: 3 : 0
l=:''
for. i. y do. l=:l,(<'.')  end.
)

ts 'l=:bld4 1e4'
5.41629 199104


If so, I agree there needs to be a more efficient way

On Mon, Mar 10, 2014 at 7:05 AM, Linda Alvord <lindaalvord at verizon.net> wrote:
>
> Raul,  Since I have a math background, I'm rather fond of  x  and  y  and am
> not in any hurry to eliminate them.
> However, I like boxes and will ponder your ideas -  at least conceptually.
>
> Thanks for all your coaching!
>
> Linda
>
>
> -----Original Message-----
> From: programming-bounces at forums.jsoftware.com
> [mailto:programming-bounces at forums.jsoftware.com] On Behalf Of bill lam
> Sent: Monday, March 10, 2014 3:30 AM
> To: Programming forum
> Subject: Re: [Jprogramming] strategies for building long lists of boxes
>
> we can build internal representation (3!:1 or 3) of the box array and
> convert it using 3!:2, not sure if this can improve time or space
> efficiency.
>
> On Mon, Mar 10, 2014 at 2:37 PM, Raul Miller <rauldmiller at gmail.com> wrote:
>> Since using , to build boxed arrays does not currently have any code to
>> support it, time is O(n^2). In other words: inefficient for long lists of
>> boxes.
>>
>> So let's say we wanted to build lists of 30000 boxes, how could we do that
>> efficiently?
>>
>> It seems to me that the right thing to do would be: pick a threshold
> (maybe
>> 1000 boxes) and when your list gets that long, append that intermediate
>> result to a result list and start a fresh instance of the working list.
>> Repeat until done (and don't forget to append the last intermediate list
> to
>> the result).
>>
>> Conceptually speaking, this is still O(n^2). But it should also be orders
>> of magnitude faster (at the cost of some complexity) than use of unadorned
>> comma. (And conceptually speaking one might be able to define some kind of
>> "infinite" representation of this algorithm which has better than O(n^2)
>> performance. Maybe O(n log n)?
>>
>> Thanks,
>>
>> --
>> Raul
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