3 * Implementation of helper classes for using the remember option
4 * in GiNaC functions */
7 * GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
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21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
33 // class remember_table_entry
36 remember_table_entry::remember_table_entry(function const & f, ex const & r)
37 : hashvalue(f.gethash()), seq(f.seq), result(r)
39 ++last_access = access_counter;
43 bool remember_table_entry::is_equal(function const & f) const
45 GINAC_ASSERT(f.seq.size()==seq.size());
46 if (f.gethash()!=hashvalue) return false;
47 for (unsigned i=0; i<seq.size(); ++i)
48 if (!seq[i].is_equal(f.seq[i])) return false;
49 ++last_access = access_counter;
54 unsigned long remember_table_entry::access_counter = 0;
57 // class remember_table_list
60 remember_table_list::remember_table_list(unsigned as, unsigned strat)
63 remember_strategy = strat;
67 void remember_table_list::add_entry(function const & f, ex const & result)
69 if ((max_assoc_size!=0) &&
70 (remember_strategy!=remember_strategies::delete_never) &&
71 (size()>=max_assoc_size)) {
72 // table is full, we must delete an older entry
73 GINAC_ASSERT(size()>0); // there must be at least one entry
75 switch (remember_strategy) {
76 case remember_strategies::delete_cyclic: {
77 // delete oldest entry (first in list)
81 case remember_strategies::delete_lru: {
82 // delete least recently used entry
83 iterator it = begin();
84 iterator lowest_access_it = it;
85 unsigned long lowest_access = (*it).get_last_access();
88 if ((*it).get_last_access()<lowest_access) {
89 lowest_access = (*it).get_last_access();
90 lowest_access_it = it;
94 erase(lowest_access_it);
97 case remember_strategies::delete_lfu: {
98 // delete least frequently used entry
99 iterator it = begin();
100 iterator lowest_hits_it = it;
101 unsigned lowest_hits = (*it).get_successful_hits();
104 if ((*it).get_successful_hits()<lowest_hits) {
105 lowest_hits = (*it).get_successful_hits();
110 erase(lowest_hits_it);
114 throw(std::logic_error("remember_table_list::add_entry(): invalid remember_strategy"));
116 GINAC_ASSERT(size()==max_assoc_size-1);
118 push_back(remember_table_entry(f,result));
121 bool remember_table_list::lookup_entry(function const & f, ex & result) const
123 for (const_iterator cit=begin(); cit!=end(); ++cit) {
124 if ((*cit).is_equal(f)) {
125 result = (*cit).get_result();
133 // class remember_table
136 remember_table::remember_table()
140 remember_strategy=remember_strategies::delete_never;
143 remember_table::remember_table(unsigned s, unsigned as, unsigned strat)
144 : max_assoc_size(as), remember_strategy(strat)
146 // we keep max_assoc_size and remember_strategy if we need to clear
149 // use some power of 2 next to s
150 table_size = 1 << log2(s);
154 bool remember_table::lookup_entry(function const & f, ex & result) const
156 unsigned entry = f.gethash() & (table_size-1);
157 GINAC_ASSERT(entry<size());
158 return operator[](entry).lookup_entry(f,result);
161 void remember_table::add_entry(function const & f, ex const & result)
163 unsigned entry = f.gethash() & (table_size-1);
164 GINAC_ASSERT(entry<size());
165 operator[](entry).add_entry(f,result);
168 void remember_table::clear_all_entries(void)
174 void remember_table::init_table(void)
177 for (unsigned i=0; i<table_size; ++i)
178 push_back(remember_table_list(max_assoc_size,remember_strategy));
181 std::vector<remember_table> & remember_table::remember_tables(void)
183 static std::vector<remember_table> * rt = new std::vector<remember_table>;