Tree-M/MT/MTcursor.cpp

/*********************************************************************
*                                                                    *
* Copyright (c) 1997,1998, 1999                                      *
* Multimedia DB Group and DEIS - CSITE-CNR,                          *
* University of Bologna, Bologna, ITALY.                             *
*                                                                    *
* All Rights Reserved.                                               *
*                                                                    *
* Permission to use, copy, and distribute this software and its      *
* documentation for NON-COMMERCIAL purposes and without fee is       *
* hereby granted provided  that this copyright notice appears in     *
* all copies.                                                        *
*                                                                    *
* THE AUTHORS MAKE NO REPRESENTATIONS OR WARRANTIES ABOUT THE        *
* SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING  *
* BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY,      *
* FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHOR  *
* SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A      *
* RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS    *
* DERIVATIVES.                                                       *
*                                                                    *
*********************************************************************/

#include "MTcursor.h"
#include "MT.h"
#include "MTpredicate.h"

class MTnode;

int
sign(double x)
{
        if(x>0) return 1;
        if(x<0) return -1;
        return 0;
}

int comparedst(dst *a, dst *b) { return sign(a->Bound()-b->Bound()); }
int comparedst(dst& a, dst& b) { return sign(a.Bound()-b.Bound()); }
int compareentry(MTentry *a, MTentry *b) { return sign(a->maxradius()-b->maxradius()); }

MTcursor::MTcursor(const MT& tree, const MTpred& query): queue(comparedst), results(compareentry), tree(tree)
{
        GiSTpath path;
        dst *d;

        path.MakeRoot();
        d=new dst(path, 0, MAXDOUBLE);
        this->query=(MTpred *)query.Copy();
        queue.Insert(d);
}

BOOL
MTcursor::IsReady() const
{
        if(queue.IsEmpty()) return (!results.IsEmpty());
        else if(results.IsEmpty()) return FALSE;
        else return (queue.First()->Bound()>=results.First()->maxradius());
}

double
MTcursor::Bound() const
{
        if(queue.IsEmpty())
                if(results.IsEmpty()) return maxDist();
                else return(results.First()->maxradius());
        else if(results.IsEmpty()) return(queue.First()->Bound());
        else return MIN(queue.First()->Bound(), results.First()->maxradius());
}

void
MTcursor::FetchNode()
{
        if(queue.IsEmpty()) return;

        int i, iprev, inext;    // these are the previous and the next entries to be examined
        dst *d=queue.RemoveFirst();
        MTnode *node=(MTnode *)tree.ReadNode(d->Path());        // retrieve next node to be examined

//      cout << "Read node " << node->Path() << ": " << d->Bound() << endl;
        // search the first children to be examined
        for(unsigned int i=0; i<node->NumEntries(); i++) {      // for each entry in the current node
                MTentry *e=(MTentry *)((*node)[i].Ptr());
                double dist=query->distance(e->object());

                if(!e->IsLeaf()) {      // insert the child node in the priority queue
                        dst *dnew;
                        GiSTpath path=node->Path();
                        double dmin=dist-e->maxradius(), dmax=dist+e->maxradius();      // these are lower- and upper-bounds on the distances of the descendants of the entry from the query object

                        if(dmin<0) dmin=0;
                        path.MakeChild(e->Ptr());
                        dnew=new dst(path, dmin, dist);
                        queue.Insert(dnew);
                }
                else {  // insert the entry in the result list
                        MTentry *key=(MTentry *)e->Copy();

                        key->setminradius(0);
                        key->setmaxradius(dist);        // we insert the actual distance from the query object as the key radius
                        results.Insert(key);
//                      cout << "Inserted (" << dist << ") into list in " << j <<"-th place\n";
                }
        }
        delete node;    // delete examined node
        delete d;
}

MTentry *
MTcursor::Next()
{
        while(!IsReady()) FetchNode();
        if(!results.IsEmpty()) return results.RemoveFirst();
        else return NULL;
}

MTcursor::~MTcursor()
{
        delete query;
        while(!results.IsEmpty()) delete results.RemoveFirst();
        while(!queue.IsEmpty()) delete queue.RemoveFirst();
}
Revision:	1.1
Committed:	Sun May 6 00:45:52 2001 UTC (23 years, 1 month ago) by root
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	/*********************************************************************
2			* *
3			* Copyright (c) 1997,1998, 1999 *
4			* Multimedia DB Group and DEIS - CSITE-CNR, *
5			* University of Bologna, Bologna, ITALY. *
6			* *
7			* All Rights Reserved. *
8			* *
9			* Permission to use, copy, and distribute this software and its *
10			* documentation for NON-COMMERCIAL purposes and without fee is *
11			* hereby granted provided that this copyright notice appears in *
12			* all copies. *
13			* *
14			* THE AUTHORS MAKE NO REPRESENTATIONS OR WARRANTIES ABOUT THE *
15			* SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING *
16			* BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, *
17			* FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHOR *
18			* SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A *
19			* RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS *
20			* DERIVATIVES. *
21			* *
22			*********************************************************************/
23
24			#include "MTcursor.h"
25			#include "MT.h"
26			#include "MTpredicate.h"
27
28			class MTnode;
29
30			int
31			sign(double x)
32			{
33			if(x>0) return 1;
34			if(x<0) return -1;
35			return 0;
36			}
37
38			int comparedst(dst a, dst b) { return sign(a->Bound()-b->Bound()); }
39			int comparedst(dst& a, dst& b) { return sign(a.Bound()-b.Bound()); }
40			int compareentry(MTentry a, MTentry b) { return sign(a->maxradius()-b->maxradius()); }
41
42			MTcursor::MTcursor(const MT& tree, const MTpred& query): queue(comparedst), results(compareentry), tree(tree)
43			{
44			GiSTpath path;
45			dst *d;
46
47			path.MakeRoot();
48			d=new dst(path, 0, MAXDOUBLE);
49			this->query=(MTpred *)query.Copy();
50			queue.Insert(d);
51			}
52
53			BOOL
54			MTcursor::IsReady() const
55			{
56			if(queue.IsEmpty()) return (!results.IsEmpty());
57			else if(results.IsEmpty()) return FALSE;
58			else return (queue.First()->Bound()>=results.First()->maxradius());
59			}
60
61			double
62			MTcursor::Bound() const
63			{
64			if(queue.IsEmpty())
65			if(results.IsEmpty()) return maxDist();
66			else return(results.First()->maxradius());
67			else if(results.IsEmpty()) return(queue.First()->Bound());
68			else return MIN(queue.First()->Bound(), results.First()->maxradius());
69			}
70
71			void
72			MTcursor::FetchNode()
73			{
74			if(queue.IsEmpty()) return;
75
76			int i, iprev, inext; // these are the previous and the next entries to be examined
77			dst *d=queue.RemoveFirst();
78			MTnode node=(MTnode )tree.ReadNode(d->Path()); // retrieve next node to be examined
79
80			// cout << "Read node " << node->Path() << ": " << d->Bound() << endl;
81			// search the first children to be examined
82			for(unsigned int i=0; i<node->NumEntries(); i++) { // for each entry in the current node
83			MTentry e=(MTentry )((*node)[i].Ptr());
84			double dist=query->distance(e->object());
85
86			if(!e->IsLeaf()) { // insert the child node in the priority queue
87			dst *dnew;
88			GiSTpath path=node->Path();
89			double dmin=dist-e->maxradius(), dmax=dist+e->maxradius(); // these are lower- and upper-bounds on the distances of the descendants of the entry from the query object
90
91			if(dmin<0) dmin=0;
92			path.MakeChild(e->Ptr());
93			dnew=new dst(path, dmin, dist);
94			queue.Insert(dnew);
95			}
96			else { // insert the entry in the result list
97			MTentry key=(MTentry )e->Copy();
98
99			key->setminradius(0);
100			key->setmaxradius(dist); // we insert the actual distance from the query object as the key radius
101			results.Insert(key);
102			// cout << "Inserted (" << dist << ") into list in " << j <<"-th place\n";
103			}
104			}
105			delete node; // delete examined node
106			delete d;
107			}
108
109			MTentry *
110			MTcursor::Next()
111			{
112			while(!IsReady()) FetchNode();
113			if(!results.IsEmpty()) return results.RemoveFirst();
114			else return NULL;
115			}
116
117			MTcursor::~MTcursor()
118			{
119			delete query;
120			while(!results.IsEmpty()) delete results.RemoveFirst();
121			while(!queue.IsEmpty()) delete queue.RemoveFirst();
122			}