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Subject: Re: [boost] [interprocess][multi_index] emplace() is not sufficient for maps
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-09-18 15:41:42

Thorsten Ottosen skrev:
> Hi Ion and Joaquín,
> This issue is related to node-based containers. I think you both have
> added emplace() to provide efficient in-place construction.
> However, I often encounter a situation where emplace() is not sufficient
> for me.

I actually got into a situation where I need another member function.
The issue arises when I use map/set as a priority_queue and want to
limit the size of the queue. In this situation I will be erasing one
element and inserting one element again and again. Unless the map/set
keeps a free-list of previously erased elements (which I don't think
they do normally) we will be deallocating and allocating a new node over
and over again.

Therefore I would like to see the follwing member:

   iterator modify_key( const_iterator element, const Key& new_key );

This function only needs to rebalance/resort the keys and can completely
avoid deallocation/allocation.



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