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1、14FloatBecausefloatissuchanimportantpartofnetworkanalysisandbecauseitisfrequentlyquoted–ormisquoted–bycomputerprotagon-istsasanotherreasonwhycomputersmustbeused,aspecialdiscussionofthesubjectmaybehelpfultothosereadersnottoofamiliarwithitsuseinpractice.Ofthethreetypesoffl
2、oatshownonaprintout,i.e.thetotalfloat,freefloatandindependentfloat,onlythefirst–thetotalfloat–isingeneraluse.Whereresourcesmoothingisrequired,aknowledgeoffreefloatcanbeuseful,sinceitistheactivitieswithfreefloatthatcanbemovedbackwardsorforwardsintimewithoutaffectinganyoth
3、eractivities.Independentfloat,ontheotherhand,isreallyquiteauselesspieceofinformationandshouldbesuppressed(whenpossible)fromanycomputerprintout.Ofthemanymanagers,siteengineersorplannersinter-viewed,nonehasbeenabletofindapracticalapplicationofindependentfloat.TotalfloatTot
4、alfloat,incontrasttoothertypesoffloat,doeshavearoletoplay.Bydefinition,itisthetimeFloatbetweentheanticipatedstart(orfinish)ofanactivityandthelatestpermissiblestart(orfinish).Thefloatcanbeeitherpositiveornegative.Apositivefloatmeansthattheoperationoractivitywillbecomplete
5、dearlierthannecessary,andanegativefloatindicatesthattheactivitywillbelate.Apredictionofthestatusofanyparticularactivityis,therefore,averyusefulandimportantpieceofinformationforamanager.However,thisinformationisoflittleuseifnottransmittedtomanagementassoonasitbecomesavail
6、able,andeverydayofdelayreducesthemanager’sabilitytorectifytheslippageorreplanthemodeofoperation.Thereasonforcallingthistypeoffloat‘totalfloat’isbecauseitisthetotalofallthe‘freefloats’inastringofactivitieswhenworkingbackfromwherethisstringmeetsthecriticalpathtotheactivity
7、inquestion.Forexample,inFigure16.2,theactivitiesintheloweststringJtoP,havethefollowingfreefloats:J=0,K=10–9=1,L=0,M=15–14=1,N=21–19=2,P=0.TotalfloatforKistherefore2+1+1+1=4.Thisisthesameasthe4showninthelowermiddlespaceofthenode.Itisveryeasytocalculatethetotalfloatsandfre
8、efloatsinaprecedenceorLesterdiagram.Foranyactivity,thetotalfloatisthedifferencebetweenthelatestfinishan
