lib-src/automata/densedfa.cc

   1 //////////////////////////////////////////////////////////////////////////////
   2 // NOTICE:
   3 //
   4 // ADLib, Prop and their related set of tools and documentation are in the
   5 // public domain.   The author(s) of this software reserve no copyrights on
   6 // the source code and any code generated using the tools.  You are encouraged
   7 // to use ADLib and Prop to develop software, in both academic and commercial
   8 // settings, and are free to incorporate any part of ADLib and Prop into
   9 // your programs.
  10 //
  11 // Although you are under no obligation to do so, we strongly recommend that
  12 // you give away all software developed using our tools.
  13 //
  14 // We also ask that credit be given to us when ADLib and/or Prop are used in
  15 // your programs, and that this notice be preserved intact in all the source
  16 // code.
  17 //
  18 // This software is still under development and we welcome any suggestions
  19 // and help from the users.
  20 //
  21 // Allen Leung
  22 // 1994
  23 //////////////////////////////////////////////////////////////////////////////
  24
  25 #include <limits.h>
  26 #include <string.h>
  27 #include <AD/automata/densedfa.h>
  28
  29 //#define DEBUGMSG(e) e
  30 #define DEBUGMSG(e)
  31
  32 //////////////////////////////////////////////////////////////////////////
  33 //  Make hidden types visible
  34 //////////////////////////////////////////////////////////////////////////
  35 typedef DenseDFA::Symbol Symbol;
  36 typedef DenseDFA::State  State;
  37
  38 //////////////////////////////////////////////////////////////////////////
  39 //  Constructor and destructor
  40 //////////////////////////////////////////////////////////////////////////
  41 DenseDFA::DenseDFA() : def(0) {}
  42 DenseDFA::~DenseDFA() { delete [] def; }
  43
  44 //////////////////////////////////////////////////////////////////////////
  45 //  Create tables for dense dfa
  46 //////////////////////////////////////////////////////////////////////////
  47 void DenseDFA::create_tables (int size, int states, Symbol min, Symbol max)
  48 {   Super::create_tables(size,states,min,max);
  49     def = new State [number_of_states];
  50     for (int i = 0; i < number_of_states; i++) def[i] = 0;
  51 }
  52
  53 //////////////////////////////////////////////////////////////////////////
  54 //  Increment the size of tables
  55 //////////////////////////////////////////////////////////////////////////
  56 void DenseDFA::grow_states(int increment)
  57 {   State * new_def = new State [number_of_states + increment];
  58     memcpy(new_def, def, number_of_states * sizeof(State));
  59     for (int i = number_of_states; i < number_of_states + increment; i++)
  60        new_def[i] = 0;
  61     delete [] def;
  62     def = new_def;
  63     Super::grow_states(increment);
  64 }
  65
  66 //////////////////////////////////////////////////////////////////////////
  67 //  Start generating tabels and initialize temporary tables
  68 //////////////////////////////////////////////////////////////////////////
  69 void DenseDFA::start()
  70 {  Super::start();
  71    number_of_symbols = max_symbol - min_symbol + 1;
  72    diffs[0]    = new State  [ number_of_symbols ];
  73    diffs[1]    = new State  [ number_of_symbols ];
  74    transitions = new State  [ number_of_symbols ];
  75    symbols     = new Symbol [ number_of_symbols ];
  76    my_delta    = new State  [ number_of_symbols ];
  77    if (number_of_symbols <= 32)
  78       max_template_diff = number_of_symbols / 3;
  79    else if (number_of_symbols <= 64)
  80       max_template_diff = number_of_symbols / 4;
  81    else
  82       max_template_diff = number_of_symbols / 5;
  83    max_template_diff = number_of_symbols / 3;
  84    max_template_diff = number_of_symbols;
  85
  86    //
  87    // Create a template for state 0, the error state
  88    //
  89    templates[0].state = 0;
  90    templates[0].delta = new State [ number_of_symbols ];
  91    templates[0].age   = 0;
  92    templates[0].uses  = 100000; // prevent us from removing this template
  93    for (int i = 0; i < number_of_symbols; i++)
  94       templates[0].delta[i] = error_state;
  95    number_of_templates = 1;
  96    misses      = 0;
  97    current_age = 0;
  98    empty_slots = true;
  99 }
 100
 101 //////////////////////////////////////////////////////////////////////////
 102 //  Finish generating tables and free up temporary tables
 103 //////////////////////////////////////////////////////////////////////////
 104 void DenseDFA::finish()
 105 {  Super::finish();
 106    for (int i = 0; i < number_of_templates; i++)
 107       delete [] templates[i].delta;
 108    delete [] diffs[0];
 109    delete [] diffs[1];
 110    delete [] transitions;
 111    delete [] symbols;
 112    delete [] my_delta;
 113 }
 114
 115 //////////////////////////////////////////////////////////////////////////
 116 //  Add a new state into the automaton
 117 //////////////////////////////////////////////////////////////////////////
 118 void DenseDFA::add_state
 119    (State s, int fan_out, const Symbol syms[], const State delta[])
 120 {  register int i;
 121    for (i = number_of_symbols - 1; i >= 0; i--)
 122       my_delta[i] = error_state;
 123    for (i = fan_out - 1; i >= 0; i--)
 124       my_delta[ syms[ i ] - min_symbol ] = delta [ i ];
 125    add_state(s, my_delta);
 126 }
 127
 128 //////////////////////////////////////////////////////////////////////////
 129 //  Add a new state into the automaton
 130 //////////////////////////////////////////////////////////////////////////
 131 void DenseDFA::add_state(State s, const State delta[])
 132 {   //
 133     // First compute the current state with the set of templates.
 134     // If one of the template is similar enough with the current state,
 135     // use the template state as the default basis.
 136     //
 137     int fan_out;                       // the fan out, or difference of fan out
 138     int available     = 0;             // index into the diffs table
 139     int best_fan_out  = INT_MAX;       //  mimimum fan out
 140     int best_template = -1;            // template that fits the best
 141     int best_diffs = 0;                // index of the minimal difference
 142     const State same_state = error_state-1;
 143     register int i;
 144     for (i = number_of_templates - 1; i >= 0; i--) {
 145        //
 146        // compute the difference between delta and the templates
 147        //
 148        register State * a_template = templates[i].delta;
 149        register State * result = diffs[available];
 150        register int j;
 151        for (fan_out = 0, j = 0; j < number_of_symbols; j++) {
 152           if (a_template[j] != delta[j]) { result[j] = delta[j]; fan_out++; }
 153           else result[j] = same_state;
 154        }
 155
 156        //
 157        // If a better template is found, update the new minimum and
 158        // switch the buffer so that the minimal difference is always
 159        // available in |diffs[best_diffs]|.
 160        //
 161        if (fan_out < best_fan_out) {
 162           best_template = i; best_fan_out = fan_out; best_diffs = available;
 163           available = 1 - available;
 164        }
 165     }
 166
 167     Bool using_template;  // Are we using a template
 168     const State * out;    // the final out transitions
 169
 170     //
 171     // Check whether a suitable template has been located.  If so,
 172     // use the template as the default state; otherwise, the error state
 173     // is the default state.
 174     //
 175     DEBUGMSG(cerr << "[best fan out = " << best_fan_out
 176                   << " max_template_diff = " << max_template_diff);
 177     if (best_template >= 0 && best_fan_out < max_template_diff) {
 178        out = diffs[best_diffs];
 179        using_template = true;
 180        templates[best_template].uses++;
 181        templates[best_template].age = current_age;
 182        DEBUGMSG(cerr << " using template " << best_template
 183                      << " uses = " << templates[best_template].uses << "]\n");
 184     } else {
 185        out = delta;
 186        using_template = false;
 187        DEBUGMSG(cerr << "]\n");
 188     }
 189
 190     //
 191     // Eliminate all transitions from the transition function that
 192     // goes to the same state as our template.
 193     //
 194     for (fan_out = 0, i = number_of_symbols - 1; i >= 0; i--)
 195        if (out[i] != same_state) {
 196           symbols[fan_out]     = i + min_symbol;
 197           transitions[fan_out] = out[i];
 198           fan_out++;
 199        }
 200
 201     //
 202     // Emit into the table using the regular sparse compression
 203     // strategy.  The idea is that hopefully we'll have a useful template
 204     // most of the time and thus being able to ``thin'' out the transitions.
 205     //
 206     Super::add_state(s, fan_out, symbols, transitions);
 207
 208     //
 209     // Emit the default state of this state, which is the state of
 210     // the template if available.
 211     //
 212     def[s] = using_template ? templates[best_template].state
 213                             : (State)error_state;
 214
 215     //
 216     // Insert new current entry into template queue if it does not
 217     // have a template and if the queue is not full.
 218     //
 219     // if ((! using_template ||
 220     //      (max_template_diff - best_fan_out) < number_of_symbols / 6)
 221     //     && number_of_templates < Max_templates) {
 222     Bool add_template =
 223        ! using_template ||
 224        best_fan_out > 1 && templates[best_template].uses > 10 ||
 225        best_fan_out >= number_of_symbols / 3;
 226
 227     if (add_template)
 228     {  if (number_of_templates < Max_templates) {
 229           // Create new template
 230           DEBUGMSG(cerr << "[creating template "
 231                         << number_of_templates << "]\n");
 232           templates[number_of_templates].state = s;
 233           templates[number_of_templates].age   = current_age;
 234           templates[number_of_templates].uses  = 0;
 235           memcpy(
 236               templates[number_of_templates].delta
 237                   = new State [ number_of_symbols ],
 238               delta,number_of_symbols * sizeof(State));
 239           number_of_templates++;
 240        } else if (empty_slots) {
 241           // Replace template with the oldest used template
 242           int min_age = 1000000;
 243           int min_use = -1;
 244           int target  = -1;
 245           for (int j = 1; j < Max_templates; j++)
 246           {  if (templates[j].age < min_age)
 247              { target = j; min_age = templates[j].age; }
 248              if (templates[j].uses == 0) { min_use = j; }
 249           }
 250           if (min_use >= 0) target = min_use;
 251           if (target > 0 && (templates[target].uses == 0 || best_fan_out > 10))
 252           {
 253              DEBUGMSG(cerr << "[replacing template " << target << " with age "
 254                            << min_age << " uses = "
 255                            << templates[target].uses << "]\n");
 256              templates[target].state = s;
 257              templates[target].age   = current_age;
 258              templates[target].uses  = 0;
 259              memcpy(templates[target].delta, delta,
 260                     number_of_symbols * sizeof(State));
 261           } //else empty_slots = false;
 262        }
 263     }
 264     current_age++;
 265 }
 266
 267 //////////////////////////////////////////////////////////////////////////
 268 //  Emit C++ code that reconstructs the tables
 269 //////////////////////////////////////////////////////////////////////////
 270 std::ostream& DenseDFA::gen_code (std::ostream& out, const char name []) const
 271 {
 272    Super::gen_code(out,name);
 273    gen_state_table(out,name,"def",def + error_state,max_state-error_state+1);
 274    return out;
 275 }
 276
 277 //////////////////////////////////////////////////////////////////////////
 278 //  Emit C++ code that reconstructs the tables (sans base)
 279 //////////////////////////////////////////////////////////////////////////
 280 std::ostream& DenseDFA::gen_check_next_tables
 281    (std::ostream& out, const char name [], const char * mytype) const
 282 {
 283    Super::gen_check_next_tables(out,name,mytype);
 284    gen_state_table(out,name,"def",def + error_state,max_state-error_state+1,
 285                    mytype);
 286    return out;
 287 }