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[10] Computing Strongly Connected Components in Pregel

Part 2

Ralf Hartmut G[ue]ting, March 12, 2019

Run this script with ~SecondoTTYBDB~ and prefix [@][%] or [@][&].

This part can be called repeatedly.

4 Computing Connected Components

4.1 Initialize MM Structures on Master

*/
query memclear()

query meminit(3000)

let Nodes = NodesPersistent feed mconsume;
let Forward = EdgesForward feed 
  createmgraph3[Source, Target, Cost, Size];
let Backward = EdgesBackward feed 
  createmgraph3[Source, Target, Cost, Size];

/*
4.2 Set Up Pregel

*/
query setupPregel(Workers);

query remotePregelCommand('query meminit(3000)');

query remotePregelCommand('let Nodes = NodesPersistent feed mconsume;');

query remotePregelCommand(
'let Forward = EdgesForward feed createmgraph3[Source, Target, Cost, Size]'
);

query remotePregelCommand(
'let Backward = EdgesBackward feed createmgraph3[Source, Target, Cost, Size]'
);

query setPregelFunction(Compute, NodePartition);


/*
4.3 Computation

4.3.1 Phase 1: Remove Singleton Components

*/
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "checkSingle", Single: 0, Value: 0]
  initPregelMessagesWorker')

query startPregel(-1)


/*

4.3.2 Phase 2: Spread the Maximum Color to Neighborhood

*/
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "resetColor", Single: 0, Value: 0]
  initPregelMessagesWorker')

query startPregel(20)

query clearPregelMessages()

/*
4.3.3 Phase 3: Confirm Color

*/
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Color, NodePartition: PartFun(.Color), 
    Message: "confirmColor", Single: .Id, Value: .Color]
  initPregelMessagesWorker')

query startPregel(-1)


/*
4.3.4 Phase 4: Create Edges in Top Level Network

*/
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition, 
    Message: "getSuccColor", Single: 0, Value: 0]
  initPregelMessagesWorker')

query startPregel(1)








query remotePregelCommand('{delete Nodes3 | let Nodes3 = 
  Nodes mfeed consume}')

{delete Nodes3 | let Nodes3 = createSDArray("Nodes3", Workers) dsummarize 
consume}



query remotePregelCommand('{delete Edges | let Edges = 
  Forward mg3feed consume}')

{delete Edges | let Edges = createSDArray("Edges", Workers) dsummarize 
  consume}

query Edges feed {e} Nodes3 feed filter[.Color = .Id] {n1} 
  itHashJoin[Source_e, Id_n1] Nodes3 feed filter[.Color = .Id] {n2} 
  itHashJoin[Target_e, Id_n2] project[Source_e, Pos_n1, Target_e, Pos_n2] 
  extend[E: create_sline(.Pos_n1, .Pos_n2)] consume






query remotePregelCommand(
 'if isDBObject("NActive") then 
    update NActive := Nodes mfeed filter[.Active] count
  else 
    let NActive = Nodes mfeed filter[.Active] count
  endif')

if isDBObject("N") then
  update N := createSDArray("NActive", Workers) getValue tie[. + ..]
else
  let N = createSDArray("NActive", Workers) getValue tie[. + ..]
endif

while N > 0 do
{
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "checkSingle", Value: 0]
  initPregelMessagesWorker')
|
query startPregel(-1)
|
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "resetColor", Value: 0]
  initPregelMessagesWorker')
|
query startPregel(-1)
|
query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "maxBack", Value: 0]
  initPregelMessagesWorker')
|
query startPregel(-1)
|
query remotePregelCommand(
  'update NActive := Nodes mfeed filter[.Active] count')
|
update N := createSDArray("NActive", Workers) getValue tie[. + ..]
|
query writeFile(nl + "Number of active nodes =" + num2string(N), 
  "NActive.txt", TRUE)
}
endwhile

/*
4.4 Overview of the Phases

----
# Phase 1: Remove Singleton Components

query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "checkSingle", Value: 0]
  initPregelMessagesWorker')

query startPregel(-1)



# Phase 2: Spread Maximum Color

query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "resetColor", Value: 0]
  initPregelMessagesWorker')

query startPregel(-1)

# Phase 3: Spread Back to Predecessors of Maximum

query remotePregelCommand('query Nodes mfeed filter[.Active]
  projectextend[; NodeId: .Id, NodePartition: .Partition]
  extend[Message: "maxBack", Value: 0]
  initPregelMessagesWorker')

query startPregel(-1);

----

*/


/*
4.5 Checking the Results

*/

query remotePregelCommand(
 'if isDBObject("NodesQ") then update NodesQ := Nodes mfeed consume
  else let NodesQ = Nodes mfeed consume
  endif')

query createSDArray("NodesQ", Workers) dsummarize head[20] consume;

let NodesQ = createSDArray("NodesQ", Workers) dsummarize consume;

if isDBObject("Colors") then 
  update Colors := createSDArray("NodesQ", Workers) 
  dsummarize  sortby[Color] groupby[Color; Anzahl: group count] consume
else let Colors = createSDArray("NodesQ", Workers) 
  dsummarize  sortby[Color] groupby[Color; Anzahl: group count] consume
endif