Disjoint Pattern Database Heuristics
Disjoint Pattern Database Heuristics
Disjoint Pattern Database Heuristics
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
comparedtoManhattandistance.Thiscomesatthecostof550megabytesof maindiagonaltoobtainthereectedvalues. ordersofmagnitude,andtherunningtimebyafactorofovertwothousand, memory.Bycontrast,thebestnon-additivepatterndatabaseheuristicused Thislastheuristicreducesthenumberofnodegenerationsbyoverfour<br />
twelvetimesfasterthansimpleManhattandistance. byCulbersonandSchaeer[1],usingasimilaramountofmemory,generated almosttentimesmorenodesthenourbestdisjointdatabase,andranonly<br />
ourmostpowerfulheuristics.Weoptimallysolvedftyrandomproblem FindingoptimalsolutionstotheTwenty-FourPuzzleisonlypracticalwith 4.2 fromeachdatabaseisthesumofthenumberofmovesneededtosolveall reectionaboutthemaindiagonal,showninFigure5.Eachgroupconsists instanceswithIDA*,usingadisjointpatterndatabaseheuristic,andits<br />
fourgroupsoftilesfromthatstate.Theoverallheuristicisthemaximum ofthevaluesfromtheoriginalandreecteddatabases.Sincethereareonly ofsixtiles,requiring127;512;000entrieseach.Foragivenstate,thevalue<br />
twodierent-shapedgroups,a23blockoftiles,andanirregularblock surroundingtheblank,weonlyhavetostoretwodierenttables,withthe ofthesetwotables.Theheuristicvaluesforthe23grouprangefrom0to remainingvaluesobtainedbymappingthetilesandtheirpositionsintoone<br />
butthesetablescouldbecompressedaswell. byteperentry,thetotalamountofmemoryforbothtablesis243megabytes, 35moves,andfortheirregulargrouptheyrangefrom0to34moves.Atone<br />
Table3showstheinitialstate,lengthoftheoptimalsolution,andnumber Figure5:<strong>Disjoint</strong><strong>Database</strong>sforTwentyFourPuzzle<br />
12
Change language