libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc

   1 // { dg-do run { target c++11 } }
   2
   3 // Copyright (C) 2012-2025 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10 //
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15 //
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20 #include <unordered_map>
  21
  22 #include <testsuite_hooks.h>
  23
  24 void test01()
  25 {
  26   typedef std::unordered_map<int, int> Map;
  27   Map m;
  28
  29   // Make sure max load factor is 1 so that reserved elements is directly
  30   // the bucket count.
  31   m.max_load_factor(1);
  32
  33   int i = -1;
  34   for (;;)
  35     {
  36       m.reserve(m.bucket_count());
  37
  38       std::size_t bkts = m.bucket_count();
  39
  40       m.reserve(bkts);
  41       VERIFY( m.bucket_count() == bkts );
  42
  43       for (++i; size_t(i) < bkts; ++i)
  44         {
  45           m.insert(std::make_pair(i, i));
  46
  47           // As long as we insert less than the reserved number of elements we
  48           // shouldn't experiment any rehash.
  49           VERIFY( m.bucket_count() == bkts );
  50
  51           VERIFY( m.load_factor() <= m.max_load_factor() );
  52         }
  53
  54       // One more element should rehash.
  55       m.insert(std::make_pair(i, i));
  56       VERIFY( m.bucket_count() != bkts );
  57       VERIFY( m.load_factor() <= m.max_load_factor() );
  58
  59       if (i > 1024)
  60         break;
  61     }
  62 }
  63
  64 int main()
  65 {
  66   test01();
  67   return 0;
  68 }