;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Kauffman's NKC Fitness Landscape demonstrated. ;; See Kauffman, Stuart (1995; 2000). ;; This NetLogo version (C) Christopher Watts, 2011 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; extensions [array] globals [ sorted-agents mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable state-colors change-colors ] breed [agents agent] breed [variables variable] directed-link-breed [ilinks ilink] directed-link-breed [vlinks vlink] agents-own [ fitness alt-fitness ] variables-own [ fitness-contributions inputs state next-state alt-state last-change owner ] ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to setup clear-all set state-colors array:from-list (list blue pink) set change-colors array:from-list (list red lime) ask patches [set pcolor white] let cur-item 0 create-agents number-of-agents [ set size 4 set shape "person" set color black ] set sorted-agents (sort agents) let small-radius 0 ifelse 1 = count agents [ ask (first sorted-agents) [setxy ((max-pxcor - min-pxcor) / 2) ((max-pycor - min-pycor) / 2)] set small-radius world-width * 0.25 ] [ layout-circle sorted-agents (world-width * 0.35) set small-radius 0.25 * min [min [distance myself] of other agents] of agents ] foreach sorted-agents [ create-variables number-of-variables-per-agent [ set size 4 set shape "circle" set owner ? create-vlink-to ? [ set color grey set hidden? true ] ] ] ; Checking parameters if k-internal-dependencies >= max [count my-in-vlinks] of agents [ user-message (word "K is too high.") stop ] if c-external-dependencies > max [(count variables) - count my-in-vlinks] of agents [ user-message (word "C is too high.") stop ] ; Define input tables and fitness contributions for each node. let sel-var nobody let ext-inputs [] let int-variables [] let ext-variables [] let cur-owner nobody ask variables [ set state (random 2) set next-state state set last-change ticks let cur-var self set cur-owner owner set int-variables ([in-vlink-neighbors] of cur-owner) with [self != cur-var] set ext-variables (variables with [owner != cur-owner]) set inputs sort (n-of k-internal-dependencies int-variables) set ext-inputs sort (n-of c-external-dependencies ext-variables) foreach inputs [ ask ? [ create-ilink-to cur-var [ set color orange if curved-links? [ set shape "input" ] ; Slows updating ] ] ] foreach ext-inputs [ ask ? [ create-ilink-to cur-var [ set color sky if curved-links? [ set shape "input" ] ] ] ] set inputs (sentence inputs ext-inputs self) ifelse simulation-type = "Boolean update"[ ; For simplicity, we code the boolean updates table as a fitness contributions table. set fitness-contributions array:from-list n-values (2 ^ (length inputs)) [random 2] ] [ set fitness-contributions array:from-list n-values (2 ^ (length inputs)) [random-float 1] ] ] ask agents [ let small-angle 360 / (count in-vlink-neighbors) let cur-var 0 ask in-vlink-neighbors [ move-to owner set heading (cur-var * small-angle) fd small-radius rt 90 set cur-var cur-var + 1 ] ] ask agents [set fitness fitness-calculation] update-stats colour-variables update-plots end to reset-agents ask variables [ set state (random 2) set next-state state set last-change ticks ] ask agents [set fitness fitness-calculation] colour-variables update-stats update-plots end to update-stats set mean-fitness mean [fitness] of agents set max-fitness max [fitness] of agents set min-fitness min [fitness] of agents set median-fitness median [fitness] of agents set stdev-fitness (ifelse-value (1 = count agents) [0] [standard-deviation [fitness] of agents]) set num-unstable count variables with [last-change >= ticks - change-threshold] end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to-report fitness-calculation let f-sum 0 ask in-vlink-neighbors [ let f-row 0 foreach inputs [ set f-row f-row * 2 set f-row f-row + ([state] of ?) ] set f-sum f-sum + (array:item fitness-contributions f-row) ] report (f-sum / (count in-vlink-neighbors)) end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to go tick if simulation-type = "Hill climb: Egoists in parallel" [parallel-hill-climb] if simulation-type = "Hill climb: One Egoist" [one-agent-hill-climb] if simulation-type = "Optimise: Egoists in parallel" [agents-optimise-in-parallel] if simulation-type = "Optimise: One Egoist" [agent-optimises] if simulation-type = "Optimise: One Egoist in turn" [agents-optimise-in-turn] if simulation-type = "Boolean update" [boolean-update] if simulation-type = "Hill climb: One Altruist" [one-agent-hill-climb-common-goal] ask variables [ if state != next-state [set last-change ticks] set state next-state ] ask agents [set fitness fitness-calculation] colour-variables update-stats update-plots end to parallel-hill-climb ask agents [ set alt-fitness fitness let flip-variable one-of in-vlink-neighbors ask flip-variable [ set alt-state state set state 1 - alt-state ] set fitness fitness-calculation ifelse fitness < alt-fitness [ ;rollback ask flip-variable [ set next-state alt-state set state alt-state ] ; set fitness alt-fitness ] [ ask flip-variable [ set next-state state set state alt-state ] ] ] end to one-agent-hill-climb ask one-of agents [ set alt-fitness fitness let flip-variable one-of in-vlink-neighbors ask flip-variable [ set alt-state state set state 1 - alt-state ] set fitness fitness-calculation ifelse fitness < alt-fitness [ ;rollback ask flip-variable [ set next-state alt-state set state alt-state ] ; set fitness alt-fitness ] [ ask flip-variable [ set next-state state set state alt-state ] ] ] end to agents-optimise-in-turn let latest-return 0 foreach sort agents [ ask ? [ ask in-vlink-neighbors [ set alt-state state ] set latest-return agent-best ask in-vlink-neighbors [ set next-state state ] ] ] end to agent-optimises let latest-return 0 ask one-of agents [ set alt-fitness fitness ask in-vlink-neighbors [ set alt-state state ] set latest-return agent-best ask in-vlink-neighbors [ set next-state state set state alt-state ] set fitness alt-fitness ] end to agents-optimise-in-parallel let latest-return 0 foreach sort agents [ ask ? [ set alt-fitness fitness ask in-vlink-neighbors [ set alt-state state ] set latest-return agent-best ask in-vlink-neighbors [ set next-state state set state alt-state ] set fitness alt-fitness ] ] end to boolean-update ask agents [ let flip-variable one-of in-vlink-neighbors ask flip-variable [ set next-state fitness-calculation ] ] end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to-report agent-best ; For current agent, cycle through all solutions and return with one of the best. let v-order array:from-list sort in-vlink-neighbors let carryover 0 let cur-node 0 let num-nodes (count in-vlink-neighbors) let unfinished true let best-fitness -1 let best-sol n-values num-nodes [0] ask in-vlink-neighbors [set state 0] set fitness fitness-calculation set best-fitness fitness set best-sol map [[state] of ?] (array:to-list v-order) while [unfinished] [ set cur-node 0 set carryover 1 while [(carryover != 0) and (cur-node < num-nodes)] [ ifelse 0 = [state] of (array:item v-order cur-node) [ ask (array:item v-order cur-node) [set state 1] set carryover 0 ] [ ask (array:item v-order cur-node) [set state 0] set carryover 1 ] set cur-node cur-node + 1 ] set unfinished not ((cur-node = num-nodes) and (carryover = 1)) set fitness fitness-calculation if fitness > best-fitness [ set best-fitness fitness set best-sol map [[state] of ?] (array:to-list v-order) ] ] foreach (array:to-list v-order) [ ask ? [ set state first best-sol ] set best-sol but-first best-sol ] set fitness best-fitness report fitness end to one-agent-hill-climb-common-goal ; Agents try to improve population's fitness ask one-of agents [ set alt-fitness fitness let alt-group-fitness sum [fitness] of agents let flip-variable one-of in-vlink-neighbors ask flip-variable [ set alt-state state set state 1 - alt-state ] set fitness fitness-calculation let group-fitness sum [fitness-calculation] of agents ifelse group-fitness < alt-group-fitness [ ;rollback ask flip-variable [ set next-state alt-state set state alt-state ] ; set fitness alt-fitness ] [ ask flip-variable [ set next-state state set state alt-state ] ] ] end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to colour-variables if Variables-Colour = "On and Off" [ ask variables [set color array:item state-colors state] ] if Variables-Colour = "Changing" [ ask variables [set color array:item change-colors (ifelse-value (last-change >= ticks - change-threshold) [1] [0])] ] end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to update-plots set-current-plot "Fitness" set-current-plot-pen "Mean" plotxy ticks mean-fitness set-current-plot-pen "Max" plotxy ticks max-fitness set-current-plot-pen "Min" plotxy ticks min-fitness if ticks > change-threshold [ set-current-plot "Instability" plotxy ticks num-unstable ] end @#$#@#$#@ GRAPHICS-WINDOW 232 10 642 441 -1 -1 4.0 1 10 1 1 1 0 0 0 1 0 99 0 99 0 0 1 ticks SLIDER 5 45 201 78 Number-Of-Agents Number-Of-Agents 1 100 1 1 1 NIL HORIZONTAL SLIDER 5 81 224 114 Number-Of-Variables-Per-Agent Number-Of-Variables-Per-Agent 1 20 5 1 1 NIL HORIZONTAL MONITOR 5 188 87 233 # Variables number-of-variables-per-agent * number-of-agents 17 1 11 BUTTON 5 240 69 273 Setup setup NIL 1 T OBSERVER NIL NIL NIL NIL SLIDER 5 117 192 150 K-Internal-Dependencies K-Internal-Dependencies 0 9 2 1 1 NIL HORIZONTAL SLIDER 5 152 195 185 C-External-Dependencies C-External-Dependencies 0 9 0 1 1 NIL HORIZONTAL MONITOR 666 197 745 242 Mean mean-fitness 5 1 11 MONITOR 747 197 827 242 Max max-fitness 5 1 11 BUTTON 5 328 68 361 Go go T 1 T OBSERVER NIL NIL NIL NIL BUTTON 71 328 140 361 Go Once go NIL 1 T OBSERVER NIL NIL NIL NIL PLOT 665 11 947 161 Fitness Time (ticks) Agent Fitness 0.0 1.0 0.0 1.0 true true PENS "Mean" 1.0 0 -16777216 true "Max" 1.0 0 -13345367 true "Min" 1.0 0 -11221820 true TEXTBOX 8 12 207 52 Kauffman's NK Fitness 16 0.0 1 INPUTBOX 5 418 160 478 Change-Threshold 10 1 0 Number CHOOSER 5 369 143 414 Variables-Colour Variables-Colour "On and Off" "Changing" 0 TEXTBOX 668 178 818 196 Agent Fitness Statistics: 11 0.0 1 CHOOSER 4 277 230 322 Simulation-Type Simulation-Type "Hill climb: Egoists in parallel" "Hill climb: One Egoist" "Optimise: Egoists in parallel" "Optimise: One Egoist" "Optimise: One Egoist in turn" "Hill climb: One Altruist" 3 BUTTON 142 328 222 361 Reset Agents reset-agents NIL 1 T OBSERVER NIL NIL NIL NIL MONITOR 92 188 223 233 # Inputs Per Variable k-internal-dependencies + c-external-dependencies + 1 17 1 11 MONITOR 747 244 827 289 Min min-fitness 5 1 11 MONITOR 666 244 745 289 Median median-fitness 5 1 11 MONITOR 829 197 909 242 Stdev stdev-fitness 5 1 11 PLOT 666 295 866 445 Instability Time (ticks) # Unstable 0.0 1.0 0.0 1.0 true false PENS "default" 1.0 0 -16777216 true MONITOR 868 295 995 340 # Unstable Variables num-unstable 17 1 11 MONITOR 868 342 996 387 % 100 * num-unstable / (count variables) 3 1 11 SWITCH 232 446 365 479 Curved-Links? Curved-Links? 1 1 -1000 @#$#@#$#@ KAUFFMAN'S NK FITNESS MODEL --------------------------- A demonstration of Stuart Kauffman's concept of NKC Fitness. (See Kauffman 1993; 1995; 2000.) More precisely, a demonstration of coadapting agents (e.g. species, firms) with a given number of traits and given numbers of interdependencies between them, leading to a tunable level difficulty in finding combinations of traits that are satisfactory to all agents in the population. This version (C) Christopher J Watts, 2011. HOW IT WORKS ------------ A number (S) of agents will try to find the most fit combination of state values for a number (N) of boolean variables. The fitness value of their set of variables is determined by tables of fitness values, with one table for each variable in the set. Each variable is a node in a network. Each node has a number of input nodes, each with its own state, on which a node variable's contribution to fitness will depend. Each node's fitness table contains one row for each combination of input states. Input nodes are chosen randomly at the start, with K inputs sampled from the agent's other variables, C inputs sampled from variables owned by other agents, and 1 input from the variable itself. Thus each node's fitness table has (2 ^ (K + C + 1)) rows. Agents start with their variables in random states. They then seek better combinations of states using heuristic search algorithms. Included here is a random-walk hill climbing algorithm, which agents may perform one agent at a time in random order (i.e. agents sequentially), or in parallel. In random-walk hill climbing, a problem-solving agent chooses one of its variables, alters the state of that variable, and calculates the resulting fitness value for its new combination of variable states. If the fitness is greater than or equal to its previous value, then the agent will adopt the new state for the variable next time tick. Otherwise, the agent will reverse the state change. State changes only become visible to other agents at the end of the time tick. If C > 0 then agents may change their states in response to other agents' changes. If agents update in parallel, then the information about input states which an agent incorporated when updating may have changed by the very next time tick, and thus what seemed at the time to be an optimal combination of states may be suboptimal after one tick. HOW TO USE IT ------------- Select the number of agents, number of variable nodes per agent, and K and C dependencies. Click "Setup". Agents, variable nodes and dependency links will be drawn. Links within an agent's set of variables are shown in orange. Links between agents' sets are shown in sky blue. Variable nodes may be coloured according to their current state (on/off), or according to whether they have changed within a given number of ticks. Click "Go" to start agents' heuristic searches for fitter variables. Click "Reset" to give agents variables randomly chosen states. THINGS TO NOTICE ---------------- If C is low (how low depends in part on K), agents should all be able to find optimal combinations of states, i.e. combinations which they do not want to change, whereupon the system stabilises. At higher values of C, agents may be unable to find a stable system state. Clicking "Reset" will make agents seek again, but from a different starting point and via different attempted changes. When stability re-emerges, agents may have stabilised on different solutions to before, with different fitness values. This reflects the fact that the fitness landscape consists of multiple peaks or local optima. THINGS TO TRY ------------- Explore the parameter space. Record the population mean and max fitness after a given number of ticks. Does the system appear to have stabilised? Is it better to update agents one at a time or in parallel? Decomposing a task: If the N is relatively low, you might like to try the option "agents optimise in turn". In this, each agent in turn is invited to search through all its possible solutions to identify the best (the global optimum), given current inputs from others. This is much quicker than searching through all possible combinations of all variables held by the population. E.g. Suppose there are 4 agents and N=5 variables per agent. There are 2 ^ N = 32 possible combinations for each agent, and 4 * 32 = 128 solutions to evaluate in total. This is much less than 2 ^ (4 * N) = 2 ^ 20 = 1048576. Does such decomposition of the problem produce good solutions for each agent? Try different values of N, K and C. How do these affect the advantage of decomposition? (Also, which is better for fitness or stability: agents optimising in turn or in parallel?) EXTENDING THE MODEL ------------------- Variable nodes have a fixed number of input nodes, which are sampled at random without preference. What if some structure or preference is followed during allocation of input nodes? What other heuristic search algorithms could our agents follow? Are any better than random-walk hill climbing? RELATED MODELS -------------- Lots of models make use of Kauffman's NK fitness landscapes! CREDITS AND REFERENCES ---------------------- Kauffman, S. (1993) The Origins of Order: Self-Organization and Selection in Evolution. New York: Oxford University Press. Kauffman, S. (1995) At Home in the Universe: The Search for Laws of Complexity. London: Penguin. Kauffman, S. (2000) Investigations. Oxford: Oxford University Press. @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 225 150 285 150 135 Line -16777216 false 150 285 150 135 Line -16777216 false 150 135 15 75 Line -16777216 false 150 135 285 75 bug true 0 Circle -7500403 true true 96 182 108 Circle -7500403 true true 110 127 80 Circle -7500403 true true 110 75 80 Line -7500403 true 150 100 80 30 Line -7500403 true 150 100 220 30 butterfly true 0 Polygon -7500403 true true 150 165 209 199 225 225 225 255 195 270 165 255 150 240 Polygon -7500403 true true 150 165 89 198 75 225 75 255 105 270 135 255 150 240 Polygon -7500403 true true 139 148 100 105 55 90 25 90 10 105 10 135 25 180 40 195 85 194 139 163 Polygon -7500403 true true 162 150 200 105 245 90 275 90 290 105 290 135 275 180 260 195 215 195 162 165 Polygon -16777216 true false 150 255 135 225 120 150 135 120 150 105 165 120 180 150 165 225 Circle -16777216 true false 135 90 30 Line -16777216 false 150 105 195 60 Line -16777216 false 150 105 105 60 car false 0 Polygon -7500403 true true 300 180 279 164 261 144 240 135 226 132 213 106 203 84 185 63 159 50 135 50 75 60 0 150 0 165 0 225 300 225 300 180 Circle -16777216 true false 180 180 90 Circle -16777216 true false 30 180 90 Polygon -16777216 true false 162 80 132 78 134 135 209 135 194 105 189 96 180 89 Circle -7500403 true true 47 195 58 Circle -7500403 true true 195 195 58 circle false 0 Circle -7500403 true true 0 0 300 circle 2 false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 cow false 0 Polygon -7500403 true true 200 193 197 249 179 249 177 196 166 187 140 189 93 191 78 179 72 211 49 209 48 181 37 149 25 120 25 89 45 72 103 84 179 75 198 76 252 64 272 81 293 103 285 121 255 121 242 118 224 167 Polygon -7500403 true true 73 210 86 251 62 249 48 208 Polygon -7500403 true true 25 114 16 195 9 204 23 213 25 200 39 123 cylinder false 0 Circle -7500403 true true 0 0 300 dot false 0 Circle -7500403 true true 90 90 120 face happy false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 255 90 239 62 213 47 191 67 179 90 203 109 218 150 225 192 218 210 203 227 181 251 194 236 217 212 240 face neutral false 0 Circle -7500403 true true 8 7 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Rectangle -16777216 true false 60 195 240 225 face sad false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 168 90 184 62 210 47 232 67 244 90 220 109 205 150 198 192 205 210 220 227 242 251 229 236 206 212 183 fish false 0 Polygon -1 true false 44 131 21 87 15 86 0 120 15 150 0 180 13 214 20 212 45 166 Polygon -1 true false 135 195 119 235 95 218 76 210 46 204 60 165 Polygon -1 true false 75 45 83 77 71 103 86 114 166 78 135 60 Polygon -7500403 true true 30 136 151 77 226 81 280 119 292 146 292 160 287 170 270 195 195 210 151 212 30 166 Circle -16777216 true false 215 106 30 flag false 0 Rectangle -7500403 true true 60 15 75 300 Polygon -7500403 true true 90 150 270 90 90 30 Line -7500403 true 75 135 90 135 Line -7500403 true 75 45 90 45 flower false 0 Polygon -10899396 true false 135 120 165 165 180 210 180 240 150 300 165 300 195 240 195 195 165 135 Circle -7500403 true true 85 132 38 Circle -7500403 true true 130 147 38 Circle -7500403 true true 192 85 38 Circle -7500403 true true 85 40 38 Circle -7500403 true true 177 40 38 Circle -7500403 true true 177 132 38 Circle -7500403 true true 70 85 38 Circle -7500403 true true 130 25 38 Circle -7500403 true true 96 51 108 Circle -16777216 true false 113 68 74 Polygon -10899396 true false 189 233 219 188 249 173 279 188 234 218 Polygon -10899396 true false 180 255 150 210 105 210 75 240 135 240 house false 0 Rectangle -7500403 true true 45 120 255 285 Rectangle -16777216 true false 120 210 180 285 Polygon -7500403 true true 15 120 150 15 285 120 Line -16777216 false 30 120 270 120 leaf false 0 Polygon -7500403 true true 150 210 135 195 120 210 60 210 30 195 60 180 60 165 15 135 30 120 15 105 40 104 45 90 60 90 90 105 105 120 120 120 105 60 120 60 135 30 150 15 165 30 180 60 195 60 180 120 195 120 210 105 240 90 255 90 263 104 285 105 270 120 285 135 240 165 240 180 270 195 240 210 180 210 165 195 Polygon -7500403 true true 135 195 135 240 120 255 105 255 105 285 135 285 165 240 165 195 line true 0 Line -7500403 true 150 0 150 300 line half true 0 Line -7500403 true 150 0 150 150 pentagon false 0 Polygon -7500403 true true 150 15 15 120 60 285 240 285 285 120 person false 0 Circle -7500403 true true 110 5 80 Polygon -7500403 true true 105 90 120 195 90 285 105 300 135 300 150 225 165 300 195 300 210 285 180 195 195 90 Rectangle -7500403 true true 127 79 172 94 Polygon -7500403 true true 195 90 240 150 225 180 165 105 Polygon -7500403 true true 105 90 60 150 75 180 135 105 plant false 0 Rectangle -7500403 true true 135 90 165 300 Polygon -7500403 true true 135 255 90 210 45 195 75 255 135 285 Polygon -7500403 true true 165 255 210 210 255 195 225 255 165 285 Polygon -7500403 true true 135 180 90 135 45 120 75 180 135 210 Polygon -7500403 true true 165 180 165 210 225 180 255 120 210 135 Polygon -7500403 true true 135 105 90 60 45 45 75 105 135 135 Polygon -7500403 true true 165 105 165 135 225 105 255 45 210 60 Polygon -7500403 true true 135 90 120 45 150 15 180 45 165 90 sheep false 0 Rectangle -7500403 true true 151 225 180 285 Rectangle -7500403 true true 47 225 75 285 Rectangle -7500403 true true 15 75 210 225 Circle -7500403 true true 135 75 150 Circle -16777216 true false 165 76 116 square false 0 Rectangle -7500403 true true 30 30 270 270 square 2 false 0 Rectangle -7500403 true true 30 30 270 270 Rectangle -16777216 true false 60 60 240 240 star false 0 Polygon -7500403 true true 151 1 185 108 298 108 207 175 242 282 151 216 59 282 94 175 3 108 116 108 target false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 Circle -7500403 true true 60 60 180 Circle -16777216 true false 90 90 120 Circle -7500403 true true 120 120 60 tree false 0 Circle -7500403 true true 118 3 94 Rectangle -6459832 true false 120 195 180 300 Circle -7500403 true true 65 21 108 Circle -7500403 true true 116 41 127 Circle -7500403 true true 45 90 120 Circle -7500403 true true 104 74 152 triangle false 0 Polygon -7500403 true true 150 30 15 255 285 255 triangle 2 false 0 Polygon -7500403 true true 150 30 15 255 285 255 Polygon -16777216 true false 151 99 225 223 75 224 truck false 0 Rectangle -7500403 true true 4 45 195 187 Polygon -7500403 true true 296 193 296 150 259 134 244 104 208 104 207 194 Rectangle -1 true false 195 60 195 105 Polygon -16777216 true false 238 112 252 141 219 141 218 112 Circle -16777216 true false 234 174 42 Rectangle -7500403 true true 181 185 214 194 Circle -16777216 true false 144 174 42 Circle -16777216 true false 24 174 42 Circle -7500403 false true 24 174 42 Circle -7500403 false true 144 174 42 Circle -7500403 false true 234 174 42 turtle true 0 Polygon -10899396 true false 215 204 240 233 246 254 228 266 215 252 193 210 Polygon -10899396 true false 195 90 225 75 245 75 260 89 269 108 261 124 240 105 225 105 210 105 Polygon -10899396 true false 105 90 75 75 55 75 40 89 31 108 39 124 60 105 75 105 90 105 Polygon -10899396 true false 132 85 134 64 107 51 108 17 150 2 192 18 192 52 169 65 172 87 Polygon -10899396 true false 85 204 60 233 54 254 72 266 85 252 107 210 Polygon -7500403 true true 119 75 179 75 209 101 224 135 220 225 175 261 128 261 81 224 74 135 88 99 wheel false 0 Circle -7500403 true true 3 3 294 Circle -16777216 true false 30 30 240 Line -7500403 true 150 285 150 15 Line -7500403 true 15 150 285 150 Circle -7500403 true true 120 120 60 Line -7500403 true 216 40 79 269 Line -7500403 true 40 84 269 221 Line -7500403 true 40 216 269 79 Line -7500403 true 84 40 221 269 x false 0 Polygon -7500403 true true 270 75 225 30 30 225 75 270 Polygon -7500403 true true 30 75 75 30 270 225 225 270 @#$#@#$#@ NetLogo 4.1.3 @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ setup go ticks = 200 timer count agents count variables mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable setup go ticks = 6400 timer count agents count variables mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable setup go ticks = 200 timer count agents count variables mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable setup go ticks = 1600 timer count agents count variables mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable setup go ticks = 2000 timer count agents count variables mean-fitness max-fitness min-fitness median-fitness stdev-fitness num-unstable @#$#@#$#@ @#$#@#$#@ default 0.0 -0.2 0 1.0 0.0 0.0 1 1.0 0.0 0.2 0 1.0 0.0 link direction true 0 Line -7500403 true 150 150 90 180 Line -7500403 true 150 150 210 180 input 4.0 -0.2 0 0.0 1.0 0.0 1 1.0 0.0 0.2 0 0.0 1.0 link direction true 0 Line -7500403 true 150 150 90 180 Line -7500403 true 150 150 210 180 @#$#@#$#@ 0 @#$#@#$#@