084_evaluating_recursive_programs

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1、Whereweare1.GraphTasks2.Ex:Histograms3.Structural5.Traversal6.Patterns7.PatternLanguages4.Ex:PageRank8.Ex:PRISM10.Representations11.Ex:PageRankinMR9.Ex:DataloginMR12.Ex:PageRankinPregelBillHowe,UW1EvaluationofRecursiveProgramsReachabilityfromagivennodeA(y):-Edge(‘w’,

2、y)A(y):-A(x),Edge(x,y)step0:A0=allnodesconnectedto‘w’wstep1:foreachnodeinA0,findneighborsstep2:foreachnodeinA1,findneighborsEvaluatingRecursiveQueries•Problemswiththisapproach–Whatiftherearecyclesinthegraph?SueTomLinBob6/17/13BillHowe,DataScience,Autumn20123Reachabil

3、ityfrom‘a’indatalogExampleofA(y):-R(‘a’,y)Semi-NaïveEvaluationA(y):-A(x),R(x,y)JoinDupe-elim6/17/2013BillHowe,UW4InMapReduce(computenext(removetheonesgenerationofnodes)we’vealreadyseen)JoinDifferenceΔAi-1mapreducemapreduceR(0)mapreducemap(0)R(1)mapAimapreduceA(1)imap

4、Anythingnew?i=i+1Driverdone6/17/2013BillHowe,UW5