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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc | |
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Diffstat (limited to 'libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc')
-rw-r--r-- | libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc b/libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc new file mode 100644 index 000000000..4efe8aae8 --- /dev/null +++ b/libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc @@ -0,0 +1,110 @@ +// -*- C++ -*- + +// Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the terms +// of the GNU General Public License as published by the Free Software +// Foundation; either version 3, or (at your option) any later +// version. + +// This library is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. + +// You should have received a copy of the GNU General Public License +// along with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + + +// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL. + +// Permission to use, copy, modify, sell, and distribute this software +// is hereby granted without fee, provided that the above copyright +// notice appears in all copies, and that both that copyright notice +// and this permission notice appear in supporting documentation. None +// of the above authors, nor IBM Haifa Research Laboratories, make any +// representation about the suitability of this software for any +// purpose. It is provided "as is" without express or implied +// warranty. + +/** + * @file hash_initial_size_example.cpp + * An example of setting an initial size for a container object. + */ + +/** + * This example shows how to set the initial size of a hash-based + * container object through its resize-policy object. + */ + +#include <cassert> +#include <ext/pb_ds/assoc_container.hpp> +#include <ext/pb_ds/hash_policy.hpp> + +using namespace std; +using namespace __gnu_pbds; + +// A simple hash functor. +// hash could serve instead of this functor, but it is not yet +// standard everywhere. +struct int_hash : public unary_function<int, size_t> +{ + inline size_t + operator()(const int& r_i) const + { return r_i; } +}; + +int main() +{ + // Resize policy type. + typedef + hash_standard_resize_policy< + // Size-policy type. + hash_exponential_size_policy<>, + // Trigger-policy type. + hash_load_check_resize_trigger<>, + /* Allow external access to size. + * This is just used in this example for using the + * get_actual_size method (which won't be accessible without + * this flag. + */ + true> + resize_policy_t; + + // A collision-probing hash table mapping ints to chars. + typedef + gp_hash_table< + int, + char, + int_hash, + equal_to< + int>, + // Combining function. + direct_mask_range_hashing<>, + // Probe function. + linear_probe_fn<>, + // Resize policy. + resize_policy_t> + map_t; + + // A resize-policy object with suggested initial size 256. + resize_policy_t res(hash_exponential_size_policy<>(256)); + + map_t g(int_hash(), + equal_to<int>(), + direct_mask_range_hashing<>(), + linear_probe_fn<>(), + res); + + // Check the actual size of the container object. In this case, this + // should be the initial size given by the size policy object. + assert(g.get_actual_size() == 256); + + // The logical size of g, though is 0 (it does not contain any elements). + assert(g.size() == 0); + + return 0; +} + |