3 // Copyright (C) 2005-2014 Free Software Foundation, Inc.
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 terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
16 // You should have received a copy of the GNU General Public License
17 // along with this library; see the file COPYING3. If not see
18 // <http://www.gnu.org/licenses/>.
21 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
23 // Permission to use, copy, modify, sell, and distribute this software
24 // is hereby granted without fee, provided that the above copyright
25 // notice appears in all copies, and that both that copyright notice
26 // and this permission notice appear in supporting documentation. None
27 // of the above authors, nor IBM Haifa Research Laboratories, make any
28 // representation about the suitability of this software for any
29 // purpose. It is provided "as is" without express or implied
33 * @file hash_resize_example.cpp
34 * An example of externally resizing a map.
38 * This example shows how to externally manipulate the size of a hash-based
39 * container object through its resize-policy object.
44 #include <ext/pb_ds/assoc_container.hpp>
45 #include <ext/pb_ds/hash_policy.hpp>
48 using namespace __gnu_pbds
;
50 // A simple hash functor.
51 // hash could serve instead of this functor, but it is not yet
52 // standard everywhere.
53 struct int_hash
: public unary_function
<int, size_t>
56 operator()(const int& r_i
) const
62 // A probing hash table mapping ints to chars.
70 // Combining function.
71 direct_mask_range_hashing
<>,
75 hash_standard_resize_policy
<
76 hash_exponential_size_policy
<>,
77 hash_load_check_resize_trigger
<>,
78 /* Allow external access to size.
79 * Without setting this to true, external resizing
87 // Check the actual size of the container object. In this case, this
88 // should be the initial size given by the size policy object.
89 assert(g
.get_actual_size() == 8);
91 // Insert some elements.
96 // Now resize the table upward.
99 // Check the actual size of the container object.
100 // For the policy used in this example, the nearest larger size than
102 assert(g
.get_actual_size() == 256);
107 // Regardless of the internal size, the logical size should be 5.
108 assert(g
.size() == 5);
110 // Now resize the table downward.
113 // Check the actual size of the container object.
114 // For the policy used in this example, the nearest larger size than
116 assert(g
.get_actual_size() == 128);
120 // Regardless of the internal size, the logical size should be 5.
121 assert(g
.size() == 6);