ginac/remember.cpp

   1 /** @file remember.cpp
   2  *
   3  *  Implementation of helper classes for using the remember option
   4  *  in GiNaC functions */
   5
   6 /*
   7  *  GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
   8  *
   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.
  13  *
  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.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program; if not, write to the Free Software
  21  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  22  */
  23
  24 #include <stdexcept>
  25
  26 #include "function.h"
  27 #include "utils.h"
  28 #include "remember.h"
  29
  30 #ifndef NO_NAMESPACE_GINAC
  31 namespace GiNaC {
  32 #endif // ndef NO_NAMESPACE_GINAC
  33
  34 //////////
  35 // class remember_table_entry
  36 //////////
  37
  38 remember_table_entry::remember_table_entry(function const & f, ex const & r)
  39   : hashvalue(f.gethash()), seq(f.seq), result(r)
  40 {
  41         ++last_access = access_counter;
  42         successful_hits = 0;
  43 }
  44
  45 bool remember_table_entry::is_equal(function const & f) const
  46 {
  47         GINAC_ASSERT(f.seq.size()==seq.size());
  48         if (f.gethash()!=hashvalue) return false;
  49         for (unsigned i=0; i<seq.size(); ++i)
  50                 if (!seq[i].is_equal(f.seq[i])) return false;
  51         ++last_access = access_counter;
  52         ++successful_hits;
  53         return true;
  54 }
  55
  56 unsigned long remember_table_entry::access_counter=0;
  57
  58 //////////
  59 // class remember_table_list
  60 //////////
  61
  62 remember_table_list::remember_table_list(unsigned as, unsigned strat)
  63 {
  64         max_assoc_size = as;
  65         remember_strategy = strat;
  66 }
  67
  68
  69 void remember_table_list::add_entry(function const & f, ex const & result)
  70 {
  71         if ((max_assoc_size!=0)&&
  72                 (remember_strategy!=remember_strategies::delete_never)&&
  73                 (size()>=max_assoc_size)) {
  74                 // table is full, we must delete an older entry
  75                 GINAC_ASSERT(size()>0); // there must be at least one entry
  76
  77                 switch (remember_strategy) {
  78                 case remember_strategies::delete_cyclic: {
  79                         // delete oldest entry (first in list)
  80                         erase(begin());
  81                         break;
  82                 }
  83                 case remember_strategies::delete_lru: {
  84                         // delete least recently used entry
  85                         iterator it = begin();
  86                         iterator lowest_access_it = it;
  87                         unsigned long lowest_access = (*it).get_last_access();
  88                         ++it;
  89                         while (it!=end()) {
  90                                 if ((*it).get_last_access()<lowest_access) {
  91                                         lowest_access = (*it).get_last_access();
  92                                         lowest_access_it = it;
  93                                 }
  94                                 ++it;
  95                         }
  96                         erase(lowest_access_it);
  97                         break;
  98                 }
  99                 case remember_strategies::delete_lfu: {
 100                         // delete least frequently used entry
 101                         iterator it = begin();
 102                         iterator lowest_hits_it = it;
 103                         unsigned lowest_hits = (*it).get_successful_hits();
 104                         ++it;
 105                         while (it!=end()) {
 106                                 if ((*it).get_successful_hits()<lowest_hits) {
 107                                         lowest_hits = (*it).get_successful_hits();
 108                                         lowest_hits_it = it;
 109                                 }
 110                                 ++it;
 111                         }
 112                         erase(lowest_hits_it);
 113                         break;
 114                 }
 115                 default:
 116                         throw(std::logic_error("remember_table_list::add_entry(): invalid remember_strategy"));
 117         }
 118                 GINAC_ASSERT(size()==max_assoc_size-1);
 119         }
 120         push_back(remember_table_entry(f,result));
 121 }
 122
 123 bool remember_table_list::lookup_entry(function const & f, ex & result) const
 124 {
 125         for (const_iterator cit=begin(); cit!=end(); ++cit) {
 126                 if ((*cit).is_equal(f)) {
 127                         result = (*cit).get_result();
 128                         return true;
 129                 }
 130         }
 131         return false;
 132 }
 133
 134 //////////
 135 // class remember_table
 136 //////////
 137
 138 remember_table::remember_table()
 139 {
 140         table_size=0;
 141         max_assoc_size=0;
 142         remember_strategy=remember_strategies::delete_never;
 143 }
 144
 145 remember_table::remember_table(unsigned s, unsigned as, unsigned strat)
 146   : max_assoc_size(as), remember_strategy(strat)
 147 {
 148         // we keep max_assoc_size and remember_strategy if we need to clear
 149         // all entries
 150
 151         // use some power of 2 next to s
 152         table_size = 1 << log2(s);
 153         init_table();
 154 }
 155
 156 bool remember_table::lookup_entry(function const & f, ex & result) const
 157 {
 158         unsigned entry = f.gethash() & (table_size-1);
 159         GINAC_ASSERT(entry<size());
 160         return operator[](entry).lookup_entry(f,result);
 161 }
 162
 163 void remember_table::add_entry(function const & f, ex const & result)
 164 {
 165         unsigned entry = f.gethash() & (table_size-1);
 166         GINAC_ASSERT(entry<size());
 167         operator[](entry).add_entry(f,result);
 168 }
 169
 170 void remember_table::clear_all_entries(void)
 171 {
 172         clear();
 173         init_table();
 174 }
 175
 176 void remember_table::init_table(void)
 177 {
 178         reserve(table_size);
 179         for (unsigned i=0; i<table_size; ++i)
 180                 push_back(remember_table_list(max_assoc_size,remember_strategy));
 181 }
 182
 183 std::vector<remember_table> & remember_table::remember_tables(void)
 184 {
 185         static std::vector<remember_table> * rt = new std::vector<remember_table>;
 186         return *rt;
 187 }
 188
 189 #ifndef NO_NAMESPACE_GINAC
 190 } // namespace GiNaC
 191 #endif // ndef NO_NAMESPACE_GINAC