[Boost-bugs] [Boost C++ Libraries] #9574: flat_set(rand_iter, rand_iter) should use reserve()

Subject: [Boost-bugs] [Boost C++ Libraries] #9574: flat_set(rand_iter, rand_iter) should use reserve()
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-01-14 22:38:23

#9574: flat_set(rand_iter,rand_iter) should use reserve()
------------------------------+------------------------
 Reporter:  marc.glisse@…     |      Owner:  igaztanaga
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  container
  Version:  Boost 1.54.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+------------------------
 Constructing a flat_set (or flat_map or etc) from random access iterators
 could reduce the reallocation cost by calling reserve.

 {{{
 #include <vector>
 #include <boost/container/flat_set.hpp>

 typedef boost::container::flat_set<int> S;
 int main(){
   std::vector<int> v{5,4,3,2,1,0};
   S s(v.begin(),v.end());
 }
 }}}

 I observed the calls to operator new, and it was called with the
 arguments: 24, 4, 8, 12, 16, 24. Those allocations take a very significant
 amount of time in my application. I would like operator new to only be
 called twice, with argument 24.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/9574>
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