tempmem.cpp

Go to the documentation of this file.

#include <portability.h>

/*************************************************************************
 * PLEASE SEE THE FILE "license.txt" (INCLUDED WITH THIS SOFTWARE PACKAGE)
 * FOR LICENSE AND COPYRIGHT INFORMATION. 
 *************************************************************************/

/*************************************************************************
 *
 *  file:  tempmem.cpp
 *
 * =======================================================================
 *  
 *             Temporary Memory and Slot routines for Soar 6
 *
 * see comments below and in soarkernel.h  
 *  
 * =======================================================================
 */

/* Debugging stuff:  #define DEBUG_SLOTS to get slot printouts */

/* #define DEBUG_SLOTS */

#include <stdlib.h>

#include "tempmem.h"
#include "kernel.h"
#include "symtab.h"
#include "gdatastructs.h"
#include "mem.h"
#include "agent.h"

/* **********************************************************************

                        Temporary Memory

********************************************************************** */

/* ======================================================================

                        Slot Management Routines

   Find_slot() looks for an existing slot for a given id/attr pair, and
   returns it if found.  If no such slot exists, it returns NIL.
   Make_slot() looks for an existing slot for a given id/attr pair,
   returns it if found, and otherwise creates a new slot and returns it.

   Mark_slot_as_changed() is called by the preference manager whenever
   the preferences for a slot change.  This updates the list of
   changed_slots and highest_goal_whose_context_changed for use by the
   decider.
====================================================================== */

slot *find_slot (Symbol *id, Symbol *attr) {
  slot *s;

  if (!id) return NIL;  /* fixes bug #135 kjh */
  for (s=id->id.slots; s!=NIL; s=s->next)
    if (s->attr==attr) return s;
  return NIL;
}

slot *make_slot (agent* thisAgent, Symbol *id, Symbol *attr) 
{
   slot *s;
   int i;
   
   /* JC: Search for a slot first.  If it exists
   *  for the given symbol, then just return it
   */
   for (s=id->id.slots; s!=NIL; s=s->next)
   {
      if (s->attr==attr) 
         return s;
   }
   
   /* JC: need to create a new slot */
   allocate_with_pool (thisAgent, &thisAgent->slot_pool, &s);
   insert_at_head_of_dll (id->id.slots, s, next, prev);
   
   /* Context slots are goals and operators; operator slots get
    *  created with a goal (see create_new_context).
    */
   if ((id->id.isa_goal) && (attr == thisAgent->operator_symbol))
   {
      s->isa_context_slot = TRUE;
   }
   else
   {
      s->isa_context_slot = FALSE;
   }

   s->changed = NIL;
   s->acceptable_preference_changed = NIL;
   s->id = id;
   s->attr = attr;
   symbol_add_ref (id);
   symbol_add_ref (attr);
   s->wmes = NIL;
   s->all_preferences = NIL;
   
   /* JC: This is the same as all_preferences
    *  except they are indexed by type.
    */
   for (i=0; i<NUM_PREFERENCE_TYPES; i++) 
      s->preferences[i] = NIL;
   
   s->impasse_type = NONE_IMPASSE_TYPE;
   s->impasse_id = NIL;
   s->acceptable_preference_wmes = NIL;
   s->marked_for_possible_removal = FALSE;

   s->wma_val_references = NIL;

   return s;  
}

void mark_slot_as_changed (agent* thisAgent, slot *s) {
  dl_cons *dc;
  
  if (s->isa_context_slot) {
    if (thisAgent->highest_goal_whose_context_changed) {
      if (s->id->id.level <
          thisAgent->highest_goal_whose_context_changed->id.level)
        thisAgent->highest_goal_whose_context_changed = s->id;
    } else {
      thisAgent->highest_goal_whose_context_changed = s->id;
    }
    s->changed = reinterpret_cast<dl_cons *>(s);  /* just make it nonzero */
  } else {
    if (! s->changed) {
      allocate_with_pool (thisAgent, &thisAgent->dl_cons_pool, &dc);
      dc->item = s;
      s->changed = dc;

      insert_at_head_of_dll (thisAgent->changed_slots, dc, next, prev);
 }
  }
}

/* -----------------------------------------------------------------
                      Slot Garbage Collection

   Old slots are garbage collected as follows:  whenever we notice that
   the last preference has been removed from a slot, we call
   mark_slot_for_possible_removal().  We don't deallocate the slot
   right away, because there might still be wmes in it, or we might
   be about to add a new preference to it (through some later action
   of the same production firing, for example).

   At the end of the phase, we call remove_garbage_slots(), which
   scans through each marked slot and garbage collects it if it has
   no wmes or preferences.
----------------------------------------------------------------- */

void mark_slot_for_possible_removal (agent* thisAgent, slot *s) {
  if (s->marked_for_possible_removal) return;
  s->marked_for_possible_removal = TRUE;
  push (thisAgent, s, thisAgent->slots_for_possible_removal);
}

void remove_garbage_slots (agent* thisAgent) {
  cons *c;
  slot *s;
  
  while (thisAgent->slots_for_possible_removal) {
    c = thisAgent->slots_for_possible_removal;
    thisAgent->slots_for_possible_removal = thisAgent->slots_for_possible_removal->rest;
    s = static_cast<slot_struct *>(c->first);
    free_cons(thisAgent, c);
    
    if (s->wmes || s->all_preferences) {
      /* --- don't deallocate it if it still has any wmes or preferences --- */
      s->marked_for_possible_removal = FALSE;
      continue;
    }
    
    /* --- deallocate the slot --- */
#ifdef DEBUG_SLOTS
    print_with_symbols (thisAgent, "\nDeallocate slot %y ^%y", s->id, s->attr);
#endif
    
    if (s->changed && (! s->isa_context_slot)) {
      remove_from_dll (thisAgent->changed_slots, s->changed, next, prev);
      free_with_pool (&thisAgent->dl_cons_pool, s->changed);
    }
    remove_from_dll (s->id->id.slots, s, next, prev);
    symbol_remove_ref (thisAgent, s->id);
    symbol_remove_ref (thisAgent, s->attr);
 if ( s->wma_val_references != NIL )
 {
   s->wma_val_references->~wma_sym_reference_map();
   free_with_pool( &( thisAgent->wma_slot_refs_pool ), s->wma_val_references );
   s->wma_val_references = NIL;
 }
    free_with_pool (&thisAgent->slot_pool, s);
  }
}