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1、COMPUTINGPRACTICESEdgarH.SibleyThestateoftheartindatacompressionisarithmeticcoding,notthebetter-PanelEditorknownHuffmanmethod.Arithmeticcodinggivesgreatercompression,isfasterforadaptivemodels,andclearlyseparatesthemodelfromthechannelencoding.ARITHMETICCODINGFORDATACOIUPRE
2、SSIONIANH.WIllEN,RADFORDM.NEAL,andJOHNG.CLEARYArithmeticcodingissuperiorinmostrespectstotheDATACOMPRESSIONbetter-knownHuffman[lo]method.Itrepresentsin-Tomany,datacompressionconjuresupanassort-formationatleastascompactly-sometimesconsid-mentofadhoctechniquessuchasconversio
3、noferablymoreso.Itsperformanceisoptimalwithoutspacesintexttotabs,creationofspecialcodesfortheneedforblockingofinputdata.Itencouragesacommonwords,orrun-lengthcodingofpicturedataclearseparationbetweenthemodelforrepresenting(e.g.,see[8]).Thiscontrastswiththemoremoderndataand
4、theencodingofinformationwithrespecttomodel-basedparadigmforcoding,where,fromanthatmodel.Itaccommodatesadaptivemodelseasilyinputstringofsymbolsandamodel,anencodedstringandiscomputationallyefficient.Yetmanyauthorsisproducedthatis(usually)acompressedversionofandpractitioners
5、seemunawareofthetechnique.theinput.Thedecoder,whichmusthaveaccesstoIndeedthereisawidespreadbeliefthatHuffmanthesamemodel,regeneratestheexactinputstringcodingcannotbeimprovedupon.fromtheencodedstring.InputsymbolsaredrawnWeaimtorectifythissituationbypresentinganfromsomewell
6、-definedsetsuchastheASCIIoraccessibleimplementationofarithmeticcodingandbinaryalphabets;theencodedstringisaplainse-bydetailingitsperformancecharacteristics.Westartquenceofbits.Themodelisawayofcalculating,inbybrieflyreviewingbasicconceptsofdatacompres-anygivencontext,thedi
7、stributionofprobabilitiessionandintroducingthemodel-basedapproachthatforthenextinputsymbol.Itmustbepossiblefortheunderliesmostmoderntechniques.Wethenoutlinedecodertoproduceexactlythesameprobabilitydis-theideaofarithmeticcodingusingasimpleexam-tributioninthesamecontext.Com
8、pressionisple,beforepresentingprogramsforbothencodingachievedbytransmittingthemoreprobablesymbol
