; package delivery problem ; by ; Jose M. Vidal breed [ deliverators ] ;"The Deliverator stands tall, your pie in thirty minutes or you can have it free, ; shoot the driver, take his car, file a class-action suit."--Snow Crash. deliverators-own [dist deliveries steps balance average-cost accepted-package packages helping behavior] ;dist is the total distance the agent has travelled ;deliveries are the set of deliveries left. They are given in [spoke distance] pairs. ;steps is used to keep track of the steps left towards the goal ;balance is a list of the balances (B in the paper). The i'th element refers to who-of agent = i. ;behavior is ; 0 - philanthropic ; 1 - selfish ; 2 - reciprocative ; 3 - individual ; patches-own [name] globals [max-distance delivery-distances spoke-mult distance-mult num-asks-multiplier average-total-cost average-total-dist num-deliverators] ;num-deliveries- deliveries are referred to as "tasks" in the paper. ;num-spokes- is the variable "R" in the paper to setup ca initialize end to initialize set max-distance 3 ;This is variable "D" in the paper set spoke-mult 360 / num-spokes set distance-mult 5 set num-asks-multiplier 10 set num-deliverators num-philanthropic + num-selfish + num-reciprocative + num-individual create-custom-deliverators num-philanthropic + num-selfish + num-reciprocative + num-individual [ ifelse (who < num-philanthropic) [ set behavior 0 ] [ ifelse (who < num-philanthropic + num-selfish) [ set behavior 1 ] [ ifelse (who < num-philanthropic + num-selfish + num-reciprocative)[ set behavior 2] [ set behavior 3]]]] set delivery-distances make-list num-deliveries ask deliverators [ set-deliveries set heading 0] ask (patch 0 0) [set name "depot"] set-plot-pen-interval 1 print "Setup done." end to-report randomize-list [lst] locals [i len num-reps a a-val b] set len length lst set num-reps len * 2 while [i < num-reps] [ set a random-int-or-float len set a-val item a lst set b random-int-or-float len set lst replace-item a lst (item b lst) set lst replace-item b lst a-val set i i + 1 ] report lst end ;Makes a list of len items by cycling over the possible distances of delivery. ;We assume only integer distances are allowed. to-report make-list [len] locals [i lst c] set lst [] set i 0 set c round (max-distance / 2) while [i < len] [ set lst fput c lst set i i + 1 set c (c + 1) mod max-distance + 1] report lst end to-report make-deliveries locals [i res] set res [] while [i < length delivery-distances][ set res fput list (random-int-or-float num-spokes) (item i delivery-distances) res set i i + 1] report randomize-list res end ;agents in the depot exchange tasks ;I had to do this using a double loop because the parallelism introduced synchronization problems. ;without-interruption is not good enough to solve this. to exchange-tasks locals [i j owners traders] ask deliverators with [name-of patch-here = "depot" and not empty? deliveries][ set accepted-package false ;true if agent has accepted a package from someone. If so, he will not try to trade his package away set packages fput (item 1 first deliveries) [] ;A list of distances for the packages Im delivering, the first is my original one set helping [] ] ;A list of who-of for the agents for whom agent has agreed to take a package set owners values-from deliverators with [name-of patch-here = "depot" and (not empty? deliveries) ] [who] set owners randomize-list owners while [not empty? owners][ set i (turtle first owners) if (not accepted-package-of i and ;If i has not accepted a package then it can still try to give his away. behavior-of i != 3)[ ;individual agents don't ask for help set traders values-from deliverators with [name-of patch-here = "depot" and not empty? deliveries and who != who-of i and first first deliveries = first first deliveries-of i] [who] while [not empty? traders][ set j (turtle first traders) ask i [ try-to-give-next-task-to-agent j] ifelse (empty? packages-of i)[ ;if I gave it then Im done set traders [] ] [ set traders butfirst traders] ] ] ask i [ if (not empty? packages) [ set steps max packages set heading (first first deliveries) * spoke-mult set deliveries but-first deliveries]] set owners butfirst owners ] end to update ;turn of the infinity button if set if (count deliverators with [empty? deliveries] = num-deliverators and count deliverators with [name-of patch-here = "depot"] = num-deliverators) [stop] ;agents in the depot exchange-tasks ;Ask all deliverators to move one step, in parallel ask deliverators [ deliver] ;Calculate average distance travelled set average-total-dist mean values-from deliverators [dist] plot average-total-dist end to evolve ct cp initialize while [count deliverators with [empty? deliveries] != num-deliverators or count deliverators with [name-of patch-here = "depot"] != num-deliverators][ update] ask deliverators [evolve-behavior] set num-philanthropic count deliverators with [behavior = 0] set num-selfish count deliverators with [behavior = 1] set num-reciprocative count deliverators with [behavior = 2] set num-individual count deliverators with [behavior = 3] end to do-plot-deliveries locals [inc] set inc 10 set-current-plot "plot1" clear-plot set num-deliveries 10 repeat 25 [ ct cp initialize while [count deliverators with [empty? deliveries] != num-deliverators or count deliverators with [name-of patch-here = "depot"] != num-deliverators][ update] set-current-plot "plot1" type num-deliveries type " - " print average-total-dist plot average-total-dist set num-deliveries num-deliveries + inc] end to do-plot-agents locals [inc] set inc 10 set-current-plot "plot1" clear-plot set num-reciprocative 10 set num-philanthropic 0 set num-selfish 0 set num-individual 0 repeat 25 [ ct cp initialize while [count deliverators with [empty? deliveries] != num-deliverators or count deliverators with [name-of patch-here = "depot"] != num-deliverators][ update] set-current-plot "plot1" type num-reciprocative type " - " print average-total-dist plot average-total-dist set num-reciprocative num-reciprocative + inc set num-deliverators num-reciprocative] end to-report get-costs-from [delivrs] locals [res] set res [] while [not empty? delivrs][ set res lput (item 1 first delivrs * 2) res set delivrs butfirst delivrs] report res end ;Report the extra cost that agnt will incurr if it accepts task, given its current task (first deliverables) ;This method is explained in the 1996 paper. to-report extra-cost [agnt task] if (first first deliveries-of agnt != first task)[ report 0] ;only report cost if they are both on the same fin ifelse (item 1 task <= item 1 first deliveries-of agnt)[ report item 1 task] ;if task is closer than mine then cost is just cost to get there [ report 2 * item 1 task - item 1 first deliveries-of agnt] ;if task is farther than mine end ;;;;;; ; Member functions for the Deliverators. ;;;;;; to set-deliveries locals [i] set deliveries make-deliveries set average-cost mean get-costs-from deliveries set steps 0 set balance [] while [i < num-deliverators][ set i i + 1 set balance lput 0 balance] end ;returns true if I am willing to take the next task from ag ;It implements eq.1 from the paper to-report willing-to-take-next-task-from [ag] locals [the-extra-cost his-task prob] ; C_{ij}^{kl} from the paper report true ;philantropic behavior set his-task first deliveries-of ag set the-extra-cost max list 0.0 (item 1 his-task - item 1 first deliveries) set prob 1.0 / (1.0 + exp ((the-extra-cost - beta * average-cost - item (who-of ag) balance)/ tau)) ; type "Prob of " ; type who ; type " taking from " ; type who-of ag ; type " is " ; print prob if (random-int-or-float 1.0 <= prob)[ report true] report false end to-report reciprocating-agent-accepts-my-next-task? [ag] locals [his-extra-cost his-task prob] ; C_{ij}^{kl} from the paper set his-task first deliveries-of ag set his-extra-cost extra-cost ag first deliveries set prob 1.0 / (1.0 + exp ((his-extra-cost - beta * average-cost-of ag - item who (balance-of ag))/ tau)) if (random-int-or-float 1.0 <= prob)[ report true] report false end to give-my-next-task-to-agent [to-agent] locals [his-extra-cost task] ; type who ; type " giving package to " ; print who-of to-agent set task first deliveries ;the task I am giving to-agent set his-extra-cost extra-cost to-agent task set (packages-of to-agent) lput (item 1 task) (packages-of to-agent) ; type "packages =" ; print (packages-of to-agent) set (accepted-package-of to-agent) true set (helping-of to-agent) lput who (helping-of to-agent) set (balance-of to-agent) replace-item who (balance-of to-agent) ((item who balance-of to-agent) - his-extra-cost) set balance replace-item (who-of to-agent) balance ((item (who-of to-agent) balance) + (2 * item 1 task)) ;update my balance of him..nice guy. set deliveries butfirst deliveries set packages [] end ;Assumes that the next task for me and ag is on the same spoke. to try-to-give-next-task-to-agent [ag] locals [my-cost his-cost] if (empty? packages-of ag) [stop] ;if ag already gave away its package then we will not give it to him if (behavior-of ag = 1 or behavior-of ag = 3)[ ;selfish or individuals do not accept packages stop] set my-cost 2 * item 1 first deliveries if (my-cost > extra-cost ag first deliveries)[ ;as per the 1996 paper ifelse (behavior-of ag = 0)[ ;philanthropic give-my-next-task-to-agent ag] [ ;reciprocating if (reciprocating-agent-accepts-my-next-task? ag)[ give-my-next-task-to-agent ag]]] end to deliver locals [willing-to-help] if (empty? packages and name-of patch-here = "depot") [ ;nothing to deliver stop] if (steps = 0)[ ;at delivery site, turn around set heading heading + 180 set packages [] ] fd distance-mult set dist dist + 1 set steps steps - 1 end to evolve-behavior locals [distances ap randa randb a b total-dist] set total-dist sum values-from deliverators [dist] set distances values-from deliverators [list who dist] set randa random-int-or-float 1.0 set randb random-int-or-float 1.0 set ap 0 while [not empty? distances][ set ap ap + (item 1 first distances / total-dist) if (randa < ap) [ set a first distances set randa 10] if (randb < ap)[ set b first distances set randb 10] set distances butfirst distances ] ifelse (1.0 / item 1 a) > (1.0 / item 1 b) [ set behavior behavior-of (turtle first a) ] [ set behavior behavior-of (turtle first b) ] end @#$#@#$#@ GRAPHICS-WINDOW 256 10 581 356 17 17 9.0 1 10 1 1 1 0 1 1 1 -17 17 -17 17 CC-WINDOW 5 393 793 488 Command Center 0 BUTTON 2 49 83 82 NIL setup NIL 1 T OBSERVER T NIL BUTTON 84 49 165 82 NIL update NIL 1 T OBSERVER T NIL BUTTON 166 49 247 82 NIL update T 1 T OBSERVER T NIL SLIDER 2 214 174 247 num-deliveries num-deliveries 0 500 50 1 1 NIL SLIDER 2 247 174 280 num-spokes num-spokes 1 20 4 1 1 NIL SLIDER 2 280 174 313 tau tau 0 1 0.75 0.01 1 NIL SLIDER 2 313 174 346 beta beta 0 1 0.5 0.01 1 NIL MONITOR 584 16 719 65 NIL average-total-dist 3 1 PLOT 584 68 784 218 plot1 x dist 0.0 100.0 0.0 100.0 true false BUTTON 2 346 126 379 Plot deliveries do-plot-deliveries NIL 1 T OBSERVER T NIL BUTTON 126 346 230 379 Plot agents do-plot-agents NIL 1 T OBSERVER T NIL SLIDER 2 115 182 148 num-philanthropic num-philanthropic 0 100 0 1 1 NIL SLIDER 2 82 174 115 num-selfish num-selfish 0 100 0 1 1 NIL SLIDER 2 148 181 181 num-reciprocative num-reciprocative 0 100 40 1 1 NIL SLIDER 2 181 174 214 num-individual num-individual 0 100 0 1 1 NIL BUTTON 174 214 255 247 NIL evolve NIL 1 T OBSERVER T NIL BUTTON 174 246 255 279 NIL evolve T 1 T OBSERVER T NIL @#$#@#$#@ Title: Reciprocity in Package Delivery Author: Jose M Vidal Description: In the package delivery problem a the agents must deliver a set of packages from a central depot. The destinations lie along one of several spokes emaniting from the central depot. The agents can exchange packages only at the depot. The cost to an agent is proportional to the number of packages carried.
The optimal solution to this problem is to choose one agent to go on each spoke and deliver all the packages scheduled for it. However, this would require completely selfless agents. In this program we study the dynamics that emerege when using different populations of selfish, philantropic, reciprocal, and individual agents behave. These results were first presented in @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 link true 0 Line -7500403 true 150 0 150 300 link direction true 0 Line -7500403 true 150 150 30 225 Line -7500403 true 150 150 270 225 ant true 0 Polygon -7500403 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 -7500403 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 -7500403 true true 149 186 128 197 114 232 134 270 149 282 166 270 185 232 171 195 149 186 Polygon -7500403 true true 225 66 230 107 159 122 161 127 234 111 236 106 Polygon -7500403 true true 78 58 99 116 139 123 137 128 95 119 Polygon -7500403 true true 48 103 90 147 129 147 130 151 86 151 Polygon -7500403 true true 65 224 92 171 134 160 135 164 95 175 Polygon -7500403 true true 235 222 210 170 163 162 161 166 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