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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_load_set_change_example.cpp

 * An example of setting and changing the load factor of a hash-based

 *    container object.

 */

/**

 * This example shows how to set and change the load-factor of

 * a hash-based container object through its resize-policy object.

 */

#include <functional>

#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()(int i) const

  { return i; }

};

int main()

{

  // A trigger policy type.

  typedef hash_load_check_resize_trigger< true> trigger_t;

  // A resize policy type.

  typedef

    hash_standard_resize_policy<

    hash_exponential_size_policy<>,

    // Trigger type.

    trigger_t,

    /* Allow external access to size.

     * This is not necessary for setting the load factor,

     * but it allows to call get_actual_size.

     */

    true>

    resize_t;

  // A collision-chaining hash table mapping ints to chars.

  typedef

    cc_hash_table<

    int,

    char,

    int_hash,

    equal_to<int>,

    // Combining function.

    direct_mask_range_hashing<>,

    // Resize policy.

    resize_t>

    map_t;

  // A trigger policy object with load between 0.3 and 0.8.

  trigger_t trigger(static_cast<float>(0.3), static_cast<float>(0.8));

  // A resize policy object with the above trigger.

  resize_t resize(hash_exponential_size_policy<>(),

                  trigger);

  map_t r_c(int_hash(),

            equal_to<int>(),

            direct_mask_range_hashing<>(),

            resize);

  r_c[1] = 'a';

  // Check the loads and sizes.

  assert(r_c.get_loads().first == static_cast<float>(0.3));

  assert(r_c.get_loads().second == static_cast<float>(0.8));

  assert(r_c.get_actual_size() == 8);

  assert(r_c.size() == 1);

  // Note that there is a discrepancy between the loads of the policy

  // object and the actual size of the container object. This is

  // because the container's construction performs an implicit

  // external resize.

  r_c[2] = 'b';

  r_c[3] = 'c';

  r_c[4] = 'd';

  assert(r_c.get_actual_size() == 8);

  // Change the loads. This causes (potentially) a resize.

  r_c.set_loads(make_pair(static_cast<float>(0.01),

                          static_cast<float>(0.05)));

  // The actual size should really change in this case.

  assert(r_c.get_actual_size() > 8);

  return 0;

}