; DisDB (Distributed Dynamic BAcktracking) for the n-queens problem ; by Ionel Muscalagiu - mionel@fih.utt.ro ; breeds [queens] globals [no-more-messages tmp nr_cicluri gata] ;rows, and cols go from [0..num-queens-1] ; ;message-queue contains the incoming messages. We take new ones out from the head. ;col is the position of the queen on it's row. ;MyContext (current-view in the ABT) is a list indexed by queen number [col0 col1 col2...] col = -1 if unknown. ;nogoods is a list of inconsistent positions [0 1 1 0 ... ] where 0 is good and 1 is no-good. ;messages-recieved is the number of messages this queen has received. queens-own [message-queue MyValue_col MyContext nogoods messages-received_ok messages-received_nogood nr_constraintc AgentC_Cost parent parent-agent children consistent ] to ComputeParent_Children locals [i] set Children [] set i who + 1 while [i < num-queens] [ set Children lput i Children set i i + 1 ] set Parent [] set i 0 while [i < who] [ set Parent lput i Parent set i i + 1 ] end to setup-patches ask patches with [(abs (pxcor + pycor)) mod 2 = 0 and pxcor < num-queens - screen-edge-x and pycor > screen-edge-y - num-queens] [ set pcolor 8] end ; n is length of list ; el is the element to-report get-list [n el] locals [i lst] set i 0 set lst [] while [i < n] [ set lst fput el lst set i i + 1] report lst end to setup-queens set nr_cicluri 0 create-custom-queens num-queens [ set MyValue_col 0 ;initial value is 0 for all. setxy (MyValue_col - screen-edge-x) (screen-edge-y - who) ;set color red set heading 0 set messages-received_ok 0 set messages-received_nogood 0 set nr_constraintc 0 set AgentC_Cost 0 set MyContext get-list num-queens -1 set nogoods get-list num-queens 0 set message-queue [] set-current-plot "Messages" create-temporary-plot-pen "q" + who set-current-plot-pen "q" + who set-plot-pen-color color] end to setup ca setup-patches setup-queens set gata false ask queens [ComputeParent_Children initialize ] end to update set no-more-messages true set nr_cicluri nr_cicluri + 1 if (nr_cicluri > Max_cycle) [Stop] ask queens [ if (not empty? message-queue)[ set no-more-messages false ] ] if (no-more-messages) [ ask queens [show MyValue_col] stop] ask queens [ handle-message ] if (gata) [ show "no solution" ask queens [show MyValue_col] stop] ask queens [ set-current-plot "Messages" create-temporary-plot-pen "q" + who plot messages-received_nogood ;plot messages-received_ok ] if (show-trace)[ print "==============" ask queens [ show "view=" + MyContext show "nogood=" + nogoods]] end to receive-message [msg] without-interruption [ set message-queue lput msg message-queue] end to-report retrieve-message locals [msg] without-interruption [ set msg first message-queue set message-queue butfirst message-queue ] report msg end to initialize locals [msg] set consistent true ;ask queens with [who > who-of myself] ; [set message-queue lput (list "info" (list (who-of myself) (MyValue_col-of myself))) message-queue ; ] foreach children [ set msg (list "info" (list who MyValue_col) ) ask turtles with [who = ? ] [receive-message msg] ] end ;this is the DisDB procedure in the paper to handle-message locals [msg xj dj] if (empty? message-queue) [stop] set msg retrieve-message if (first msg = "stop") [set gata true stop] if (first msg = "info") [set messages-received_ok messages-received_ok + 1 GoAHead msg] if (first msg = "back") [ set messages-received_nogood messages-received_nogood + 1 ResolveConflict item 1 msg] end ;this is the CheckAgentView procedure in the ABT algorithm to GoAHead [msg ] locals [xj dj i j TempValue ] if (msg != "" ) [ set xj item 0 (item 1 msg) set dj item 1 (item 1 msg) ;set nr_constraintc nr_constraintc + who * (num-queens + 1) UpdateContextInfo xj dj ] if (not consistent ) [ set TempValue ChooseValue ifelse (TempValue > -1 ) [ set MyValue_col TempValue foreach children [ set msg (list "info" (list who MyValue_col) ) ask turtles with [who = ? ] [receive-message msg] ] ] [ResolveNogoods] ] end to UpdateContextInfo [Qj Vj ] locals [i j ] set MyContext replace-item Qj MyContext Vj ;set i Qj set consistent true ;show MyValue_col + " " + current-view set i 0 while [ i < who ] ;for each queen [ if ( abs (who - i) = abs (MyValue_col - (item i MyContext)));diagonal match [ set consistent false ] if ( MyValue_col = (item i MyContext) );verticle match [ set consistent false ] set i i + 1 ] set nogoods get-list num-queens 0 set i 0 while [ i < who ] ;for each queen [set j 0 while [ j < num-queens ] ;for each column [ if ( abs (who - i) = abs (j - (item i MyContext)));diagonal match [set nogoods replace-item j nogoods 1] if ( j = (item i MyContext) );verticle match [set nogoods replace-item j nogoods 1] set j (j + 1)] set i (i + 1)] end to ResolveConflict [msgNogood ] locals [ i j msg TempValue] ;if it is consistent with the agent view, otherwise it is discarded due to obsolescence. set i 0 while [i < who] [if ((item i msgNogood) != (item i MyContext)) [stop] set i (i + 1)] ;An accepted nogood is used to update the agent view of agents not in PArent ;Update MyContext ;if (MyValue_col > -1) set nogoods replace-item MyValue_col nogoods 1 ;mark current position as no good set consistent false set TempValue ChooseValue ifelse (TempValue > -1 ) [ set MyValue_col TempValue set msg (list "info" (list who MyValue_col) ) foreach children [ ask turtles with [who = ? ] [receive-message msg] ] ] [ResolveNogoods] end ;this is the BackTrack procedure in the ABT algorithm to ResolveNogoods locals [msg i j ] ifelse (who = 0);newNogood=empty; [set gata true set msg "stop" receive-message msg ] [ set msg (list "back" MyContext ) ask turtles with [who = who-of myself - 1] [receive-message msg] ] ;set nr_constraintc nr_constraintc + who * num-queens UpdateContextConflict end to UpdateContextConflict locals [i j msg] set nogoods get-list num-queens 0 set i 0 while [ i < who ] ;for each queen [set j 0 while [ j < num-queens ] ;for each column [ if ( abs (who - i) = abs (j - (item i MyContext)));diagonal match [set nogoods replace-item j nogoods 1] if ( j = (item i MyContext) );verticle match [set nogoods replace-item j nogoods 1] set j (j + 1)] set i (i + 1)] set i 0 set j 0 while [ i < num-queens and j = 0] [if ( item i nogoods = 0 ) [set Myvalue_col i setxy (MyValue_col - screen-edge-x) (screen-edge-y - who) set msg list "info" (list who MyValue_col) ;ask turtles with [who > who-of myself] ; [receive-message msg] foreach children [ ask turtles with [who = ? ] [receive-message msg] ] set j 1] set i (i + 1)] end to-report ChooseValue locals [i j ] set i 0 set j 0 while [ i < num-queens and j = 0] [if ( item i nogoods = 0 ) [ setxy (i - screen-edge-x) (screen-edge-y - who) set j 1 report i ] set i (i + 1)] ; setxy (i - screen-edge-x) (screen-edge-y - who) report -1 end @#$#@#$#@ GRAPHICS-WINDOW 305 10 885 551 9 8 30.0 1 10 1 1 1 CC-WINDOW 809 10 1019 598 Command Center BUTTON 2 10 83 43 NIL setup NIL 1 T OBSERVER T SLIDER 2 45 174 78 num-queens num-queens 0 16 8 1 1 NIL BUTTON 82 10 163 43 NIL update NIL 1 T OBSERVER T BUTTON 163 10 245 45 NIL update T 1 T OBSERVER T SWITCH 4 78 136 111 show-trace show-trace 1 1 -1000 PLOT 18 256 296 575 Messages Nr de cicluri Mesaje nogood pe agent 0.0 10.0 0.0 10.0 true false PENS "Messages" 1.0 2 -16777216 true "default" 1.0 0 -16777216 true MONITOR 176 47 276 96 Msgs nogood sum (values-from queens [messages-received_nogood]) 0 1 MONITOR 176 99 242 148 Msgs ok sum (values-from queens [messages-received_ok]) 3 1 MONITOR 5 114 116 163 Number of cycles nr_cicluri 0 1 SLIDER 4 174 176 207 Max_cycle Max_cycle 0 1000000 1000000 1 1 NIL @#$#@#$#@ Title: NQueens DisDB (Distributed Dynamic Backtracking) Author: Muscalagiu Ionel Description: This is the N-Queens problem solution using Distributed Dynamic Backtracking-DisDB as outlined in @#$#@#$#@ default true 0 Polygon -7566196 true true 150 5 40 250 150 205 260 250 ant true 0 Polygon -7566196 true true 136 61 129 46 144 30 119 45 124 60 114 82 97 37 132 10 93 36 111 84 127 105 172 105 189 84 208 35 171 11 202 35 204 37 186 82 177 60 180 44 159 32 170 44 165 60 Polygon -7566196 true true 150 95 135 103 139 117 125 149 137 180 135 196 150 204 166 195 161 180 174 150 158 116 164 102 Polygon -7566196 true true 149 186 128 197 114 232 134 270 149 282 166 270 185 232 171 195 149 186 149 186 Polygon -7566196 true true 225 66 230 107 159 122 161 127 234 111 236 106 Polygon -7566196 true true 78 58 99 116 139 123 137 128 95 119 Polygon -7566196 true true 48 103 90 147 129 147 130 151 86 151 Polygon -7566196 true true 65 224 92 171 134 160 135 164 95 175 Polygon -7566196 true true 235 222 210 170 163 162 161 166 208 174 Polygon -7566196 true true 249 107 211 147 168 147 168 150 213 150 arrow true 0 Polygon -7566196 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 bee true 0 Polygon -256 true false 151 152 137 77 105 67 89 67 66 74 48 85 36 100 24 116 14 134 0 151 15 167 22 182 40 206 58 220 82 226 105 226 134 222 Polygon -16777216 true false 151 150 149 128 149 114 155 98 178 80 197 80 217 81 233 95 242 117 246 141 247 151 245 177 234 195 218 207 206 211 184 211 161 204 151 189 148 171 Polygon -7566196 true true 246 151 241 119 240 96 250 81 261 78 275 87 282 103 277 115 287 121 299 150 286 180 277 189 283 197 281 210 270 222 256 222 243 212 242 192 Polygon -16777216 true false 115 70 129 74 128 223 114 224 Polygon -16777216 true false 89 67 74 71 74 224 89 225 89 67 Polygon -16777216 true false 43 91 31 106 31 195 45 211 Line -1 false 200 144 213 70 Line -1 false 213 70 213 45 Line -1 false 214 45 203 26 Line -1 false 204 26 185 22 Line -1 false 185 22 170 25 Line -1 false 169 26 159 37 Line -1 false 159 37 156 55 Line -1 false 157 55 199 143 Line -1 false 200 141 162 227 Line -1 false 162 227 163 241 Line -1 false 163 241 171 249 Line -1 false 171 249 190 254 Line -1 false 192 253 203 248 Line -1 false 205 249 218 235 Line -1 false 218 235 200 144 bird1 false 0 Polygon -7566196 true true 2 6 2 39 270 298 297 298 299 271 187 160 279 75 276 22 100 67 31 0 bird2 false 0 Polygon -7566196 true true 2 4 33 4 298 270 298 298 272 298 155 184 117 289 61 295 61 105 0 43 boat1 false 0 Polygon -1 true false 63 162 90 207 223 207 290 162 Rectangle -6524078 true false 150 32 157 162 Polygon -16776961 true false 150 34 131 49 145 47 147 48 149 49 Polygon -7566196 true true 158 33 230 157 182 150 169 151 157 156 Polygon -7566196 true true 149 55 88 143 103 139 111 136 117 139 126 145 130 147 139 147 146 146 149 55 boat2 false 0 Polygon -1 true false 63 162 90 207 223 207 290 162 Rectangle -6524078 true false 150 32 157 162 Polygon -16776961 true false 150 34 131 49 145 47 147 48 149 49 Polygon -7566196 true true 157 54 175 79 174 96 185 102 178 112 194 124 196 131 190 139 192 146 211 151 216 154 157 154 Polygon -7566196 true true 150 74 146 91 139 99 143 114 141 123 137 126 131 129 132 139 142 136 126 142 119 147 148 147 boat3 false 0 Polygon -1 true false 63 162 90 207 223 207 290 162 Rectangle -6524078 true false 150 32 157 162 Polygon -16776961 true false 150 34 131 49 145 47 147 48 149 49 Polygon -7566196 true true 158 37 172 45 188 59 202 79 217 109 220 130 218 147 204 156 158 156 161 142 170 123 170 102 169 88 165 62 Polygon -7566196 true true 149 66 142 78 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109 165 110 Polygon -7566196 true true 216 83 267 123 248 143 215 107 Polygon -7566196 true true 167 163 145 234 183 234 183 163 Polygon -7566196 true true 195 163 195 233 227 233 206 159 sheep false 15 Rectangle -1 true true 90 75 270 225 Circle -1 true true 15 75 150 Rectangle -16777216 true false 81 225 134 286 Rectangle -16777216 true false 180 225 238 285 Circle -16777216 true false 1 88 92 spacecraft true 0 Polygon -7566196 true true 150 0 180 135 255 255 225 240 150 180 75 240 45 255 120 135 thin-arrow true 0 Polygon -7566196 true true 150 0 0 150 120 150 120 293 180 293 180 150 300 150 truck-down false 0 Polygon -7566196 true true 225 30 225 270 120 270 105 210 60 180 45 30 105 60 105 30 Polygon -8716033 true false 195 75 195 120 240 120 240 75 Polygon -8716033 true false 195 225 195 180 240 180 240 225 truck-left false 0 Polygon -7566196 true true 120 135 225 135 225 210 75 210 75 165 105 165 Polygon -8716033 true false 90 210 105 225 120 210 Polygon -8716033 true false 180 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Rectangle -7566196 true true 120 210 243 214 Rectangle -7566196 true true 115 114 255 120 Rectangle -7566196 true true 128 108 248 114 Rectangle -7566196 true true 150 105 225 108 Rectangle -7566196 true true 132 214 155 270 Rectangle -7566196 true true 110 260 132 270 Rectangle -7566196 true true 210 214 232 270 Rectangle -7566196 true true 189 260 210 270 Line -7566196 true 263 127 281 155 Line -7566196 true 281 155 281 192 wolf-left false 3 Polygon -6524078 true true 117 97 91 74 66 74 60 85 36 85 38 92 44 97 62 97 81 117 84 134 92 147 109 152 136 144 174 144 174 103 143 103 134 97 Polygon -6524078 true true 87 80 79 55 76 79 Polygon -6524078 true true 81 75 70 58 73 82 Polygon -6524078 true true 99 131 76 152 76 163 96 182 104 182 109 173 102 167 99 173 87 159 104 140 Polygon -6524078 true true 107 138 107 186 98 190 99 196 112 196 115 190 Polygon -6524078 true true 116 140 114 189 105 137 Rectangle -6524078 true true 109 150 114 192 Rectangle -6524078 true true 111 143 116 191 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65 195 52 170 45 150 44 128 55 121 69 121 81 135 Polygon -6524078 true true 48 143 58 141 Polygon -6524078 true true 46 136 68 137 Polygon -6524078 true true 45 129 35 142 37 159 53 192 47 210 62 238 80 237 Line -16777216 false 74 237 59 213 Line -16777216 false 59 213 59 212 Line -16777216 false 58 211 67 192 Polygon -6524078 true true 38 138 66 149 Polygon -6524078 true true 46 128 33 120 21 118 11 123 3 138 5 160 13 178 9 192 0 199 20 196 25 179 24 161 25 148 45 140 Polygon -6524078 true true 67 122 96 126 63 144 @#$#@#$#@ NetLogo 2.0.2 @#$#@#$#@ @#$#@#$#@ @#$#@#$#@