crossovr.c

Genetic Programing of music

          cd->sc2->context_method ( SELECT_CLEAN, cd->sc2, NULL, NULL );
}

/* operator_crossover()
 *
 * performs the crossover, inserting one or both offspring into the
 * new population.
 */

void operator_crossover ( population *oldpop, population *newpop,
                         void *data )
{
     crossover_data * cd;
     int p1, p2;
     int ps1, ps2;
     int l1, l2;
     lnode *st[3];
     int sts1, sts2;
     int ns1, ns2;
     int badtree1, badtree2;
     double total;
     int forceany1, forceany2;
     int repcount;
     int f, t1, t2, j;
     double r, r2;
     int totalnodes1, totalnodes2;
     int i;

     /* get the crossover-specific data structure. */
     cd = (crossover_data *)data;
     total = cd->internal + cd->external;

     /* choose a function set. */
     r = random_double() * cd->treetotal;
     for ( f = 0; r >= cd->func[f]; ++f );

     /* fill in the "treecumul" array, zeroing all trees which
	don't use the selected function set. */
     r = 0.0;
     t1 = 0;
     for ( j = 0; j < tree_count; ++j )
     {
          if ( tree_map[j].fset == f )
               r = (cd->treecumul[j] = r + cd->tree[j]);
          else
               cd->treecumul[j] = r;
     }

     /* select the first and second trees. */
     r2 = random_double() * r;
     for ( t1 = 0; r2 >= cd->treecumul[t1]; ++t1 );
     r2 = random_double() * r;
     for ( t2 = 0; r2 >= cd->treecumul[t2]; ++t2 );

#ifdef DEBUG_CROSSOVER
     printf ( "selected function set %d --> t1: %d; t2: %d\n", f, t1, t2 );
#endif
     
     /* choose two parents */
     p1 = cd->sc->select_method ( cd->sc );
     ps1 = oldpop->ind[p1].tr[t1].nodes;
     /* if the tree only has one node, we obviously can't do
	fucntionpoint crossover.  use anypoint instead. */
     forceany1 = (ps1==1||total==0.0);
     
     p2 = cd->sc2->select_method ( cd->sc2 );
     ps2 = oldpop->ind[p2].tr[t2].nodes;
     forceany2 = (ps2==1||total==0.0);

#ifdef DEBUG_CROSSOVER
     fprintf ( stderr, "parent 1 is:\n" );
     print_individual ( oldpop->ind+p1, stderr );
     fprintf ( stderr, "parent 2 is:\n" );
     print_individual ( oldpop->ind+p2, stderr );
#endif

     while(1)
     {
          
          /* choose two crossover points */

          if ( forceany1 )
          {
	       /* choose any point. */
               l1 = random_int ( ps1 );
               st[1] = get_subtree ( oldpop->ind[p1].tr[t1].data, l1 );
          }
          else if ( total*random_double() < cd->internal )
          {
	       /* choose an internal point. */
               l1 = random_int ( tree_nodes_internal (oldpop->ind[p1].tr[t1].data) );
               st[1] = get_subtree_internal ( oldpop->ind[p1].tr[t1].data, l1 );
          }
          else
          {
	       /* choose an external point. */
               l1 = random_int ( tree_nodes_external (oldpop->ind[p1].tr[t1].data) );
               st[1] = get_subtree_external ( oldpop->ind[p1].tr[t1].data, l1 );
          }
                                
          if ( forceany2 )
          {
	       /* choose any point on second parent. */
               l2 = random_int ( ps2 );
               st[2] = get_subtree ( oldpop->ind[p2].tr[t2].data, l2 );
          }
          else if ( total*random_double() < cd->internal )
          {
	       /* choose internal point. */
               l2 = random_int ( tree_nodes_internal (oldpop->ind[p2].tr[t2].data) );
               st[2] = get_subtree_internal ( oldpop->ind[p2].tr[t2].data, l2 );
          }
          else
          {
	       /* choose external point. */
               l2 = random_int ( tree_nodes_external (oldpop->ind[p2].tr[t2].data) );
               st[2] = get_subtree_external ( oldpop->ind[p2].tr[t2].data, l2 );
          }

#ifdef DEBUG_CROSSOVER
          printf ( "subtree 1 is: " );
          print_tree ( st[1], stdout );
          printf ( "subtree 2 is: " );
          print_tree ( st[2], stdout );
#endif

	  /* count the nodes in the selected subtrees. */
          sts1 = tree_nodes ( st[1] );
          sts2 = tree_nodes ( st[2] );

	  /* calculate the sizes of the offspring. */
          ns1 = ps1 - sts1 + sts2;
          ns2 = ps2 - sts2 + sts1;

          totalnodes1 = ns1;
          totalnodes2 = ns2;

#ifdef DEBUG_CROSSOVER
          printf ( "newtree 1 has size %d; limit is %d\n",
                  ns1, tree_map[t1].nodelimit );
#endif

	  /** validate the first offspring against the tree node and depth
	    limits; set "badtree1" if any are violated. **/
	  
          badtree1 = 0;
          if ( tree_map[t1].nodelimit > -1 && ns1 > tree_map[t1].nodelimit )
               badtree1 = 1;
          else if ( tree_map[t1].depthlimit > -1 )
          {
               ns1 = tree_depth_to_subtree ( oldpop->ind[p1].tr[t1].data, st[1] ) +
                     tree_depth ( st[2] );
#ifdef DEBUG_CROSSOVER
               printf ( "newtree 1 has depth %d; limit is %d\n",
                       ns1, tree_map[t1].depthlimit );
#endif
               if ( ns1 > tree_map[t1].depthlimit )
                    badtree1 = 1;
          }

	  /* if we're supposed to keep trying, skip up and choose new crossover
	     points. */
          if ( cd->keep_trying && badtree1 )
               continue;

	  /** validate the second offspring against the tree node and depth
	    limits; set "badtree2" if any are violated. **/
	  
          badtree2 = 0;
          if ( tree_map[t2].nodelimit > -1 && ns2 > tree_map[t2].nodelimit )
               badtree2 = 1;
          else if ( tree_map[t2].depthlimit > -1 )
          {
               ns2 = tree_depth_to_subtree ( oldpop->ind[p2].tr[t2].data, st[2] ) +
                     tree_depth ( st[1] );
               if ( ns2 > tree_map[t2].depthlimit )
                    badtree2 = 1;
          }

	  /* if we're supposed to keep trying, skip up and choose new crossover
	     points. */
	  
          if ( cd->keep_trying && badtree2 )
               continue;

	  /* check both offspring against the individual node limits, set
	     badtree1 and/or badtree2 if either is too big. */
	  
          if ( ind_nodelimit > -1 )
          {
               for ( i = 0; i < tree_count; ++i )
               {
                    if ( i != t1 )
                         totalnodes1 += oldpop->ind[p1].tr[i].nodes;
                    if ( i != t2 )
                         totalnodes2 += oldpop->ind[p2].tr[i].nodes;
               }
               badtree1 |= (totalnodes1 > ind_nodelimit);
               badtree2 |= (totalnodes2 > ind_nodelimit);
#ifdef DEBUG_CROSSOVER
               printf ( "newind 1 has %d nodes; limit is %d\n",
                       totalnodes1, ind_nodelimit );
#endif
          }

	  /* choose new crossover points if either tree is too big. */
          if ( cd->keep_trying && (badtree1 || badtree2) )
               continue;
          
          /* copy the first parent to the first offspring position */
          duplicate_individual ( newpop->ind+newpop->next,
                                oldpop->ind+p1 );
          if ( !badtree1 )
          {
	       /* if the first offspring is allowable... */
	       
#ifdef DEBUG_CROSSOVER
               fprintf ( stderr, "offspring 1 is allowable.\n" );
#endif
	       
	       /* make a copy of the crossover tree, replacing the
		  selected subtree with the crossed-over subtree. */
               copy_tree_replace_many ( 0, oldpop->ind[p1].tr[t1].data,
                                       st+1, st+2, 1, &repcount );
               if ( repcount != 1 )
               {
		    /* this can't happen, but check anyway. */
                    error ( E_FATAL_ERROR,
                           "botched crossover:  this can't happen" );
               }

               /* free the appropriate tree of the new individual */
               free_tree ( newpop->ind[newpop->next].tr+t1 );
               /* copy the crossovered tree to the freed space */
               gensp_dup_tree ( 0, newpop->ind[newpop->next].tr+t1 );

	       /* the new individual's fitness fields are of course invalid. */
               newpop->ind[newpop->next].evald = EVAL_CACHE_INVALID;
               newpop->ind[newpop->next].flags = FLAG_NONE;
          }
          else
          {
	       /* offspring too big but keep_trying not set, just leave the copied
		  parent 1 in the offspring position. */
#ifdef DEBUG_CROSSOVER
               fprintf ( stderr, "offspring 1 is too big; copying parent 1.\n" );
#endif
          }

	  /* we've just filled in one member of the new population. */
          ++newpop->next;
          
#ifdef DEBUG_CROSSOVER
          fprintf ( stderr, "offspring 1:" );
          if ( newpop->ind[newpop->next-1].evald == EVAL_CACHE_VALID )
               fprintf ( stderr, "  (valid)\n" );
          else
               fprintf ( stderr, "  (invalid)\n" );
          print_individual ( newpop->ind+(newpop->next-1), stderr );
#endif          

	  /* if the new population needs another member (it's not full) */
          if ( newpop->next < newpop->size )
          {
	       /* copy the second parent to the second offspring position. */
               duplicate_individual ( newpop->ind+newpop->next,
                                     oldpop->ind+p2 );
               if ( !badtree2 )
               {
		    /* if the second offspring is allowable... */
#ifdef DEBUG_CROSSOVER
                    fprintf ( stderr, "offspring 2 is allowable.\n" );
#endif
		    /* then make a copy of the tree, replacing the crossover
		       subtree. */
                    copy_tree_replace_many ( 0, oldpop->ind[p2].tr[t2].data,
                                            st+2, st+1, 1, &repcount );
                    if ( repcount != 1 )
                    {
                         error ( E_FATAL_ERROR,
                                "bad crossover:  this can't happen" );
                    }

		    /* free the old tree in the new individual, and replace
		       it with the crossover tree. */
                    free_tree ( newpop->ind[newpop->next].tr+t2 );
                    gensp_dup_tree ( 0, newpop->ind[newpop->next].tr+t2 );
                    
                    newpop->ind[newpop->next].evald = EVAL_CACHE_INVALID;
                    newpop->ind[newpop->next].flags = FLAG_NONE;
               }
               else
               {
		    /* offspring too big but keep_trying not set; just leave
		       the copy of parent 2 where it is. */
#ifdef DEBUG_CROSSOVER
                    fprintf ( stderr, "offspring 2 is big; copying parent 2.\n" );
#endif
               }
               
               ++newpop->next;
               
#ifdef DEBUG_CROSSOVER
               fprintf ( stderr, "offspring 2:" );
               if ( newpop->ind[newpop->next-1].evald == EVAL_CACHE_VALID )
                    fprintf ( stderr, "  (valid)\n" );
               else
                    fprintf ( stderr, "  (invalid)\n" );
               print_individual ( newpop->ind+(newpop->next-1), stderr );
#endif          
          
          }
#ifdef DEBUG_CROSSOVER
          else
          {
	       /* the first offspring filled the population, discard the
		  second. */
               fprintf ( stderr, "offspring 2 not needed.\n\n" );
          }
#endif

          break;
     }

#ifdef DEBUG_CROSSOVER
     printf ( "CROSSOVER COMPLETE.\n\n\n" );
#endif
     
}