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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libstdc++-v3/testsuite/ext/pb_ds/example/hash_initial_size.cc
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+// -*- 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;
+}
+