+/** @file remember.cpp
+ *
+ * Implementation of helper classes for using the remember option
+ * in GiNaC functions */
+
+/*
+ * GiNaC Copyright (C) 1999-2000 Johannes Gutenberg University Mainz, Germany
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <stdexcept>
+
+#include "function.h"
+#include "utils.h" // for log_2
+#include "remember.h"
+
+#ifndef NO_NAMESPACE_GINAC
+namespace GiNaC {
+#endif // ndef NO_NAMESPACE_GINAC
+
+//////////
+// class remember_table_entry
+//////////
+
+remember_table_entry::remember_table_entry(function const & f, ex const & r) :
+ hashvalue(f.gethash()), seq(f.seq), result(r)
+{
+ last_access=access_counter++;
+ successful_hits=0;
+}
+
+bool remember_table_entry::is_equal(function const & f) const
+{
+ GINAC_ASSERT(f.seq.size()==seq.size());
+ if (f.gethash()!=hashvalue) return false;
+ for (unsigned i=0; i<seq.size(); ++i) {
+ if (!seq[i].is_equal(f.seq[i])) return false;
+ }
+ last_access=access_counter++;
+ successful_hits++;
+ return true;
+}
+
+unsigned long remember_table_entry::access_counter=0;
+
+//////////
+// class remember_table_list
+//////////
+
+remember_table_list::remember_table_list(unsigned as, unsigned strat)
+{
+ max_assoc_size=as;
+ remember_strategy=strat;
+}
+
+
+void remember_table_list::add_entry(function const & f, ex const & result)
+{
+ if ((max_assoc_size!=0)&&
+ (remember_strategy!=remember_strategies::delete_never)&&
+ (size()>=max_assoc_size)) {
+ // table is full, we must delete an older entry
+ GINAC_ASSERT(size()>0); // there must be at least one entry
+
+ switch (remember_strategy) {
+ case remember_strategies::delete_cyclic:
+ // delete oldest entry (first in list)
+ erase(begin());
+ break;
+ case remember_strategies::delete_lru:
+ {
+ // delete least recently used entry
+ iterator it=begin();
+ iterator lowest_access_it=it;
+ unsigned long lowest_access=it->get_last_access();
+ ++it;
+ while (it!=end()) {
+ if (it->get_last_access()<lowest_access) {
+ lowest_access=it->get_last_access();
+ lowest_access_it=it;
+ }
+ ++it;
+ }
+ erase(lowest_access_it);
+ }
+ break;
+ case remember_strategies::delete_lfu:
+ {
+ // delete least frequently used entry
+ iterator it=begin();
+ iterator lowest_hits_it=it;
+ unsigned lowest_hits=it->get_successful_hits();
+ ++it;
+ while (it!=end()) {
+ if (it->get_successful_hits()<lowest_hits) {
+ lowest_hits=it->get_successful_hits();
+ lowest_hits_it=it;
+ }
+ ++it;
+ }
+ erase(lowest_hits_it);
+ }
+ break;
+ default:
+ throw(std::logic_error("remember_table_list::add_entry(): invalid remember_strategy"));
+ }
+ GINAC_ASSERT(size()==max_assoc_size-1);
+ }
+ push_back(remember_table_entry(f,result));
+}
+
+bool remember_table_list::lookup_entry(function const & f, ex & result) const
+{
+ for (const_iterator cit=begin(); cit!=end(); ++cit) {
+ if (cit->is_equal(f)) {
+ result=cit->get_result();
+ return true;
+ }
+ }
+ return false;
+}
+
+//////////
+// class remember_table
+//////////
+
+remember_table::remember_table()
+{
+ table_size=0;
+ max_assoc_size=0;
+ remember_strategy=remember_strategies::delete_never;
+}
+
+remember_table::remember_table(unsigned s, unsigned as, unsigned strat) :
+ max_assoc_size(as), remember_strategy(strat)
+{
+ // we keep max_assoc_size and remember_strategy if we need to clear
+ // all entries
+
+ // use some power of 2 next to s
+ table_size=1 << log2(s);
+ init_table();
+}
+
+bool remember_table::lookup_entry(function const & f, ex & result) const
+{
+ unsigned entry=f.gethash() & (table_size-1);
+ GINAC_ASSERT(entry<size());
+ return operator[](entry).lookup_entry(f,result);
+}
+
+void remember_table::add_entry(function const & f, ex const & result)
+{
+ unsigned entry=f.gethash() & (table_size-1);
+ GINAC_ASSERT(entry<size());
+ operator[](entry).add_entry(f,result);
+}
+
+void remember_table::clear_all_entries(void)
+{
+ clear();
+ init_table();
+}
+
+void remember_table::init_table(void)
+{
+ reserve(table_size);
+ for (unsigned i=0; i<table_size; ++i) {
+ push_back(remember_table_list(max_assoc_size,remember_strategy));
+ }
+}
+
+vector<remember_table> & remember_table::remember_tables(void)
+{
+ static vector<remember_table> * rt=new vector<remember_table>;
+ return *rt;
+}
+
+#ifndef NO_NAMESPACE_GINAC
+} // namespace GiNaC
+#endif // ndef NO_NAMESPACE_GINAC
git://www.ginac.de / ginac.git / commitdiff