Re: associative array

[Andrew Janke]

On 3/26/20 4:25 PM, José Abílio Matos wrote:
> On Thursday, 26 March 2020 20.00.39 WET Francesco Potortì wrote:
> 
>> I need an associative array, and I tried with structs, with the field
> 
>> names as keys.
> 
>>
> 
>> Unfortunately it clearly slows down with size. I have about 30000 keys,
> 
>> for each I first check if it's already there, if not I create it, if
> 
>> it's there I add some data. The number of operations (insertion +
> 
>> updates) is around 55000. The slowdown appears to be quadratic (but I
> 
>> have not made any measurement, in fact).
> 
>>
> 
>> Are there more efficient ways to build and update an associative array?
> 
>  
> 
> How about containers.Map:
> 
> https://octave.org/doc/v5.2.0/containers_002eMap.html

That's a reasonable idea, but I'm curious as to why struct itself is
slow. I would think that struct lookups for get or set would be O(1)
using a hash on the string key (or some other symbol-level identifier).
Are structs not hashtables over the string key values?

Cheers,
Andrew