Re: [boost] [ boost ] [ Trie ]

Subject: Re: [boost] [ boost ] [ Trie ]
From: Cosmin Boaca (boost.cosmin.boaca_at_[hidden])
Date: 2015-03-04 18:55:36

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.

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.

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.

Looking forward to your feedback about the ideas above.

Thank you,
Cosmin