Re: Question about arrays and no. of elements

[Ken Thomas <kst@ecs.soton.ac.uk>]

On May 15, 4:19 pm, amal.alpho...@gmail.com wrote:
> If I define an array with say a million elements, and I only put data
> in 10 of them, is it actually a waste of space/time with the array or
> does Ada only create elements when there is data to put in (so it is
> efficient)?

It will be a waste of space because you may limit the size of problem
you can solve with your resources.

It may be a waste of time if you perform operations on the whole array
such as scaling. You have only defined 10 elements and given default
values to the remaining 10^6 - 10 elements.

Why not use a more suitable data structure such as a Map
(Ada.Containers.Ordered_Maps)?
I have used these to handle large sparse matrices that cannot be
stored as dense arrays. I have not found any significant degradation
of runtime performance and I don't think you will for such a small
map.

Ken