gomp-20050608-branch/libstdc++-v3/testsuite/ext/pb_assoc/example/hash_load_set_change.cc

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005 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 2, 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 COPYING.  If not, write to the Free
  18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  31
  32 // Permission to use, copy, modify, sell, and distribute this software
  33 // is hereby granted without fee, provided that the above copyright
  34 // notice appears in all copies, and that both that copyright notice and
  35 // this permission notice appear in supporting documentation. None of
  36 // the above authors, nor IBM Haifa Research Laboratories, make any
  37 // representation about the suitability of this software for any
  38 // purpose. It is provided "as is" without express or implied warranty.
  39
  40 /**
  41  * @file hash_load_set_change_example.cpp
  42  * An example of setting and changing the load factor of a hash-based
  43  *      container object.
  44  */
  45
  46 // For cc_hash_assoc_cntnr.
  47 #include <ext/pb_assoc/assoc_cntnr.hpp>
  48 /*
  49  * For hash_standard_resize_policy, hash_exponential_size_policy,
  50  *      and direct_mask_range_hashing.
  51  */
  52 #include <ext/pb_assoc/hash_policy.hpp>
  53 // For unary_function.
  54 #include <functional>
  55 // For assert
  56 #include <cassert>
  57
  58 /*
  59  * A simple hash functor.
  60  *      std::hash could serve instead of this functor,
  61  *      but it is not yet standard everywhere.
  62  */
  63 struct int_hash : public std::unary_function<
  64   int,
  65              size_t>
  66 {
  67   inline size_t
  68   operator()(int i) const
  69   {
  70     return (i);
  71   }
  72 };
  73
  74 int
  75 main()
  76 {
  77   // A trigger policy type.
  78   typedef pb_assoc::hash_load_check_resize_trigger< true> trigger_t;
  79
  80   // A resize policy type.
  81   typedef
  82     pb_assoc::hash_standard_resize_policy<
  83     pb_assoc::hash_exponential_size_policy<>,
  84     // Trigger type.
  85     trigger_t,
  86     /* Allow external access to size.
  87      *  This is not necessary for setting the load factor,
  88      *  but it allows to call get_actual_size.
  89      */
  90     true>
  91     resize_t;
  92
  93   /*
  94    * A collision-chaining hash table mapping ints to chars.
  95    */
  96   typedef
  97     pb_assoc::cc_hash_assoc_cntnr<
  98     int,
  99     char,
 100     int_hash,
 101     std::equal_to<int>,
 102     // Combining function.
 103     pb_assoc::direct_mask_range_hashing<>,
 104     // Resize policy.
 105     resize_t>
 106     map_t;
 107
 108   // A trigger policy object with load between 0.3 and 0.8.
 109   trigger_t trigger(static_cast<float>(0.3), static_cast<float>(0.8));
 110
 111   // A resize policy object with the above trigger.
 112   resize_t resize(pb_assoc::hash_exponential_size_policy<>(),
 113                   trigger);
 114
 115   map_t c(int_hash(),
 116           std::equal_to<int>(),
 117           pb_assoc::direct_mask_range_hashing<>(),
 118           resize);
 119
 120   c[1] = 'a';
 121
 122   // Check the loads and sizes.
 123
 124   assert(c.get_loads().first == static_cast<float>(0.3));
 125   assert(c.get_loads().second == static_cast<float>(0.8));
 126
 127   assert(c.get_actual_size() == 8);
 128
 129   assert(c.size() == 1);
 130
 131   /*
 132    * Note that there is a discrepancy between the loads of the policy
 133    *    object and the actual size of the container object. This is
 134    *    because the container's construction performs an implicit external
 135    *    resize.
 136    */
 137
 138   c[2] = 'b';
 139   c[3] = 'c';
 140   c[4] = 'd';
 141
 142   assert(c.get_actual_size() == 8);
 143
 144   // Change the loads. This causes (potentially) a resize.
 145   c.set_loads(std::make_pair(
 146                              static_cast<float>(0.01),
 147                              static_cast<float>(0.05)));
 148
 149   // The loads actually changed.
 150   assert(c.get_actual_size() > 8);
 151 }
 152