Thinking SmallThe Processes for Creating Small Memory Software思维小 创建小型内存软件地过程.pdf

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1、ThinkingSmallTheProcessesforCreatingSmallMemorySoftware©2004CharlesWeir,JamesNoble.Abstract:Thispaperdescribessomeprocesspatternsforteamstofollowwhencreatingsoftwaretoruninlimitedmemory.Itisadraftversionofachaptertoaddtotheauthors’bookSmallMemorySoftware,andfollowst

2、hestructureofotherchaptersinthatbook.MajorTechnique:ThinkingSmallA.k.aSmallmethodology,‘Real’programming.Howshouldyouapproachasmallsystem?·You’redevelopingasystemthatwillbememory-constrained.·Therearemanycompetingconstraintstosatisfy·Ifdifferentdeveloperstakediffere

3、ntviewsonwhichthingstooptimise,theywillproduceaninconsistentsystemthatsatisfiesnoneoftheconstraints.You'reworkingonaprojectandyoususpecttherewillberesourcelimitationsinthetargetsystem.Forexample,thedevelopersofthe‘Super-spy007’versionfortheStrap-it-Onwrist-mountedco

4、mputerfaceasystemwithonly200KbofRAMand2MbROM.Howaretheytoadjudicatethedemandsofthevoicerecognitionsoftware,thevocabulariesandthesoftware-basedradio,tomakeitasecretagent'sdreamtoy?ShouldtheystorethevocabulariesinROMtosaveRAMspace,orkeeptheminRAMtoallowthemtochangefro

5、mRussiantoArabiconthefly?What,inshort,isimportantintheirsystem,andwhatislessso?Inmanyprojectsit’sclearfromtheoutsetthatthedevelopmentteamwillhavetospendatleastsometimeandeffortsatisfyingthesystem’smemorylimitations.Youhavetocutyourcoattofityourcloth.Yetiftheteamjust

6、spendslotsofeffortoptimisingeverythingtoworkinverylimitedmemory,they'llwastealotoftimeormaybeproduceaproductthatcouldhavebeenmuchbetter.Worsestilltheproductmayfailtoworkatallbecausetheyhavebeenoptimisingthewrongthing.Forexample,anyofthefollowingfacilitiesmaybelimite

7、d:·Heap(RAM)spaceforthewholesystem·Heapspaceforindividualprocesses(ifthemaximumheapsizeofaprocessisfixed)·Processstacksize·Secondarystorageuse·ROMspace(forprogramsthatexecutefromROM)Optimisingoneofthesewilloftenbeatacostfromoneoftheothers.Inadditiontechniquesthatopt

8、imisememoryusewilltendtocompromisetime-performance,usabilityorboth.Inanysystemthearchitectswillhavetomoderatethedemandsofdifferentcomponen