GSL containers: was Re: [Help-gsl] Linear least squares, webpages and the next release

[John D Lamb <J.D.Lamb@johndlamb.net>]

On 26/10/15 15:13, Patrick Alken wrote:
>> Yes. I’d be happy to look at redesign of the GSL containers. What’s
>> needed?
>>
>
> There was a discussion on gsl-discuss some time back, see:
>
> https://www.sourceware.org/ml/gsl-discuss/2014-q2/
>
> Gerard may have already done some work on this, or have some ideas on a
> good starting point, so I suggest getting in touch with him too (cc'd).


I’d forgotten the detail of that discussion.

I can think of a way to change the gsl block/vector/matrix alloc 
functions to be more efficient. In essence it is a pool allocator.
It would keep a record, for each power k of two up to some limit n, of 
the number of blocks allocated for sizes 2^k to 2^{k+1} together with a 
capacity (also a power of two) for blocks of that range. These would 
form linked lists of allocated and unallocated blocks. Given a request 
for a new block, if an unallocated one was available, it would be 
allocated. Otherwise the capacity would be doubled. When a block is 
freed, memory is only deallocated if no more than a quarter of capacity 
is used or if no blocks are used.

This idea needs more input.

I can’t think of a good way to create gsl_vectors and the like in stack 
memory. Of course, it is always possible to create a struct and 
initialise it.

I also don’t know of a good, easy solution to the problem of constness.

-- 
John D Lamb