You Wang | db927a5 | 2016-02-26 11:03:28 -0800 | [diff] [blame] | 1 | """ |
| 2 | Graph algorithm implementations for CHOTestMonkey |
| 3 | Author: you@onlab.us |
| 4 | """ |
| 5 | class GraphHelper: |
| 6 | """ |
| 7 | This class implements graph algorithms for CHOTestMonkey. |
| 8 | It reads main.devices and main.links as vertices and edges. |
| 9 | Currently it offers functions for finding (non-)cut-edges and vertices, |
| 10 | which is realized based on chain-decomposition algorithm |
| 11 | """ |
| 12 | def __init__( self ): |
| 13 | # Depth-first index of each node |
| 14 | self.DFI = [] |
| 15 | # Parent vertex and egde of each node in depth-first search tree |
| 16 | self.parentDeviceInDFS = [] |
| 17 | self.parentLinkInDFS = [] |
| 18 | # Data structures for chain-decomposition algorithm |
| 19 | self.backEdges = {} |
| 20 | self.chains = [] |
| 21 | self.currentDFI = 0 |
| 22 | self.upDevices = [] |
| 23 | for device in main.devices: |
| 24 | if device.isUp(): |
| 25 | self.upDevices.append( device ) |
| 26 | for i in range( len( main.devices ) ): |
| 27 | self.DFI.append( -1 ) |
| 28 | self.parentDeviceInDFS.append( None ) |
| 29 | self.parentLinkInDFS.append( None ) |
| 30 | |
| 31 | def genDFIandBackEdge( self, device ): |
| 32 | """ |
| 33 | This function runs a depth-first search and get DFI of each node |
| 34 | as well as collect the back edges |
| 35 | """ |
| 36 | self.DFI[ device.index ] = self.currentDFI |
| 37 | self.currentDFI += 1 |
| 38 | for link in device.outgoingLinks: |
| 39 | if not link.isUp(): |
| 40 | continue |
| 41 | backwardLink = link.backwardLink |
| 42 | neighbor = link.deviceB |
| 43 | if neighbor == self.parentDeviceInDFS[ device.index ]: |
| 44 | continue |
| 45 | elif self.DFI[ neighbor.index ] == -1: |
| 46 | self.parentDeviceInDFS[ neighbor.index ] = device |
| 47 | self.parentLinkInDFS[ neighbor.index ] = backwardLink |
| 48 | self.genDFIandBackEdge( neighbor ) |
| 49 | else: |
| 50 | key = self.DFI[ neighbor.index ] |
| 51 | if key in self.backEdges.keys(): |
| 52 | if not link in self.backEdges[ key ] and\ |
| 53 | not backwardLink in self.backEdges[ key ]: |
| 54 | self.backEdges[ key ].append( backwardLink ) |
| 55 | else: |
| 56 | tempKey = self.DFI[ device.index ] |
| 57 | if tempKey in self.backEdges.keys(): |
| 58 | if not link in self.backEdges[ tempKey ] and\ |
| 59 | not backwardLink in self.backEdges[ tempKey ]: |
| 60 | self.backEdges[ key ] = [ backwardLink ] |
| 61 | else: |
| 62 | self.backEdges[ key ] = [ backwardLink ] |
| 63 | |
| 64 | def findChains( self ): |
| 65 | """ |
| 66 | This function finds all the 'chains' for chain-decomposition algorithm |
| 67 | """ |
| 68 | keyList = self.backEdges.keys() |
| 69 | keyList.sort() |
| 70 | deviceIsVisited = [] |
| 71 | for i in range( len( main.devices ) ): |
| 72 | deviceIsVisited.append( 0 ) |
| 73 | for key in keyList: |
| 74 | backEdgeList = self.backEdges[ key ] |
| 75 | for link in backEdgeList: |
| 76 | chain = [] |
| 77 | currentLink = link |
| 78 | sourceDevice = link.deviceA |
| 79 | while True: |
| 80 | currentDevice = currentLink.deviceA |
| 81 | nextDevice = currentLink.deviceB |
| 82 | deviceIsVisited[ currentDevice.index ] = 1 |
| 83 | chain.append( currentLink ) |
| 84 | if nextDevice == sourceDevice or deviceIsVisited[ nextDevice.index ] == 1: |
| 85 | break |
| 86 | currentLink = self.parentLinkInDFS[ nextDevice.index ] |
| 87 | self.chains.append( chain ) |
| 88 | |
| 89 | def getNonCutEdges( self ): |
| 90 | """ |
| 91 | This function returns all non-cut-edges of a graph |
| 92 | """ |
| 93 | assert len( self.upDevices ) != 0 |
| 94 | self.genDFIandBackEdge( self.upDevices[ 0 ] ) |
| 95 | self.findChains() |
| 96 | nonCutEdges = [] |
| 97 | for chain in self.chains: |
| 98 | for link in chain: |
| 99 | nonCutEdges.append( link ) |
| 100 | return nonCutEdges |
| 101 | |
| 102 | def getNonCutVertices( self ): |
| 103 | """ |
| 104 | This function returns all non-cut-vertices of a graph |
| 105 | """ |
| 106 | nonCutEdges = self.getNonCutEdges() |
| 107 | nonCutVertices = [] |
| 108 | for device in self.upDevices: |
| 109 | deviceIsNonCut = True |
| 110 | for link in device.outgoingLinks: |
| 111 | if link.isUp() and not ( link in nonCutEdges or link.backwardLink in nonCutEdges ): |
| 112 | deviceIsNonCut = False |
| 113 | break |
| 114 | if deviceIsNonCut: |
| 115 | nonCutVertices.append( device ) |
| 116 | return nonCutVertices |
| 117 | |
| 118 | def printDFI( self ): |
| 119 | print self.DFI |
| 120 | |
| 121 | def printParentInDFS( self ): |
| 122 | print self.parentInDFS |
| 123 | |
| 124 | def printBackEdges( self ): |
| 125 | print self.backEdges |
| 126 | |
| 127 | def printChains( self ): |
| 128 | chainIndex = 0 |
| 129 | for chain in self.chains: |
| 130 | print chainIndex |
| 131 | for link in chain: |
| 132 | print link |
| 133 | chainIndex += 1 |