[SR-Users] Syntax issue?

[Igor Potjevlesch]

That's a clear pragmatic approach. Thank you.

Regards,

Igor.

-----Message d'origine-----
De : sr-users [mailto:sr-users-bounces at lists.sip-router.org] De la part de
Alex Balashov
Envoyé : mardi 17 février 2015 00:25
À : sr-users at lists.sip-router.org
Objet : Re: [SR-Users] Syntax issue?

On 02/16/2015 04:51 PM, Igor Potjevlesch wrote:

> Thank you Alex.
>
> I'm not sure to understand the parameter "size" associated to the
hashtable.
>
> I have setup 4. So, I understand that I can have 2^4 entries. Does it 
> mean that, if the table is composed with $ci+$ft, I can have 16 
> concurrent calls store into the table?

Not exactly. The size refers to the number of unique buckets in the hash
table. Entries do not have to be in unique buckets; however, insofar as the
aim of a hash table is to provide O(1) lookup capability, it is desirable,
from the point of view of the algorithmic concept, to have sufficient
buckets to accommodate this. Even a very good hash algorithm can only
compute to so many unique buckets if there are very few of them.

This is functionality that you take for granted in high-level interpreted
languages, e.g. %hashes in Perl or $associative_arrays[] in PHP. The
computer science underpinnings are exposed here at a more low level. If you
really want to understand the idea behind the htable module and why it has
that name:

    http://en.wikipedia.org/wiki/Hash_table

If you're interested only in the applied dimension and not the formal
properties, then the guidance is: provide enough bucket space to accommodate
at least the maximal number of elements you reasonably expect to store
concurrently. The memory allocation per bucket is trivial nowadays, so you
really don't need to worry about this. For example, if you expect to store
5000 elements concurrently, just provide
2^13 (8192) buckets.

-- Alex

--
Alex Balashov - Principal
Evariste Systems LLC
235 E Ponce de Leon Ave
Suite 106
Decatur, GA 30030
United States

Tel: +1-678-954-0670
Web: http://www.evaristesys.com/, http://www.alexbalashov.com/

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