]>
Commit | Line | Data |
---|---|---|
36fed23c | 1 | // -*- C++ -*- |
2 | ||
f1717362 | 3 | // Copyright (C) 2005-2016 Free Software Foundation, Inc. |
36fed23c | 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 terms | |
7 | // of the GNU General Public License as published by the Free Software | |
6bc9506f | 8 | // Foundation; either version 3, or (at your option) any later |
36fed23c | 9 | // version. |
10 | ||
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. | |
15 | ||
16 | // You should have received a copy of the GNU General Public License | |
6bc9506f | 17 | // along with this library; see the file COPYING3. If not see |
18 | // <http://www.gnu.org/licenses/>. | |
36fed23c | 19 | |
36fed23c | 20 | |
21 | // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL. | |
22 | ||
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 | |
30 | // warranty. | |
31 | ||
32 | /** | |
33 | * @file hash_initial_size_example.cpp | |
34 | * An example of setting an initial size for a container object. | |
35 | */ | |
36 | ||
37 | /** | |
38 | * This example shows how to set the initial size of a hash-based | |
39 | * container object through its resize-policy object. | |
40 | */ | |
41 | ||
42 | #include <cassert> | |
43 | #include <ext/pb_ds/assoc_container.hpp> | |
44 | #include <ext/pb_ds/hash_policy.hpp> | |
45 | ||
46 | using namespace std; | |
b34535d7 | 47 | using namespace __gnu_pbds; |
36fed23c | 48 | |
49 | // A simple hash functor. | |
50 | // hash could serve instead of this functor, but it is not yet | |
51 | // standard everywhere. | |
52 | struct int_hash : public unary_function<int, size_t> | |
53 | { | |
54 | inline size_t | |
55 | operator()(const int& r_i) const | |
56 | { return r_i; } | |
57 | }; | |
58 | ||
59 | int main() | |
60 | { | |
61 | // Resize policy type. | |
62 | typedef | |
63 | hash_standard_resize_policy< | |
64 | // Size-policy type. | |
65 | hash_exponential_size_policy<>, | |
66 | // Trigger-policy type. | |
67 | hash_load_check_resize_trigger<>, | |
68 | /* Allow external access to size. | |
69 | * This is just used in this example for using the | |
70 | * get_actual_size method (which won't be accessible without | |
71 | * this flag. | |
72 | */ | |
73 | true> | |
74 | resize_policy_t; | |
75 | ||
76 | // A collision-probing hash table mapping ints to chars. | |
77 | typedef | |
78 | gp_hash_table< | |
79 | int, | |
80 | char, | |
81 | int_hash, | |
82 | equal_to< | |
83 | int>, | |
84 | // Combining function. | |
85 | direct_mask_range_hashing<>, | |
86 | // Probe function. | |
87 | linear_probe_fn<>, | |
88 | // Resize policy. | |
89 | resize_policy_t> | |
90 | map_t; | |
91 | ||
92 | // A resize-policy object with suggested initial size 256. | |
93 | resize_policy_t res(hash_exponential_size_policy<>(256)); | |
94 | ||
95 | map_t g(int_hash(), | |
96 | equal_to<int>(), | |
97 | direct_mask_range_hashing<>(), | |
98 | linear_probe_fn<>(), | |
99 | res); | |
100 | ||
101 | // Check the actual size of the container object. In this case, this | |
102 | // should be the initial size given by the size policy object. | |
103 | assert(g.get_actual_size() == 256); | |
104 | ||
105 | // The logical size of g, though is 0 (it does not contain any elements). | |
106 | assert(g.size() == 0); | |
107 | ||
108 | return 0; | |
109 | } | |
110 |