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Subject: Re: [boost] [ boost ] [ Trie ]
From: Antony Polukhin (antoshkka_at_[hidden])
Date: 2015-03-05 02:15:11

2015-03-05 2:55 GMT+03:00 Cosmin Boaca <boost.cosmin.boaca_at_[hidden]>:

> Hello,
> I have modified the directory strucure. I think it's ok right now.
> > Another significant and hard task:
> > trie_node structure looks too heavy: there are too many member variables.
> > Try to simplify trie_node and value_list_node structures. Think of a
> > possible optimizations of the trie_node structure for
> trie_set|trie_map|trie_multiset|trie_multimap.
> > For example all the sets do not require values, so pointers to value list
> nodes can be removed from trie_set in that case.
> I have thought of this task too. I will share with you some ideas in order
> to get some feedback about them.
> 1. Value = void specialization for trie_node which would remove pointers to
> value_list_head/tail, self_value_count.


> 2. Another specialization or something like this would be ok for trie_map
> also. The map_node should only contain a member
> value_type value. value_list_head/tail, self_value_count should be removed
> in this case to but I don't know how to specialize the template (for which
> key, value) type.


How about adding aditional template parameter to map node. Something like

template <class Key, class Value, bool IsMulty>
class map_node;

> 3. Considering 2, trie_multiset could be easily implemented in terms of
> trie_map<key, int>, maybe using private inheritance. The int would keep
> track of the frequency of the key prefix.


> 4. value_count could be completely removed but this would greatly reduce
> the performance of count_prefix function. In my opinion this shouldn't be
> removed.

This is discussable. Let's solve this some time later.

> I don't know too much about pred_node, next_node, and the
> child_iter_of_parrent. I need to take some more time to look at those
> things to see if any of them could be removed. I see that pred_node and
> next_node are used in trie_iterator and child_iter_of_parrent is used to
> maintain the values of pred_node and next_node. However, I don't know which
> would be the tradeofs of the removal for each of them.

Let's eat an elephant part by part. There's more than enough tasks right
now, even without *_node and child_iter_of_parrent.

> Looking forward to your feedback about the ideas above.

Good progress! Trie library becoming better and better.

Best regards,
Antony Polukhin

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