The wolf, the goat, and the cabbage
Model was written in NetLogo 5.0.3
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NETLOGO GOALS EXAMPLE (WITH PLANNING)
This example is explained in the tutorials at http://scientificgems.wordpress.com/2014/01/24/agent-goals-in-netlogo-the-wolf-the-goat-and-the-cabbage/ and http://scientificgems.wordpress.com/2014/01/25/planning-in-netlogo-the-wolf-the-goat-and-the-cabbage-again/
RUNNING IT
Click SETUP to start, and GO to execute. Execution speed should be set fairly slow.
Comments and Questions
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turtles-own [ speed ;; agent speed in cells per tick goal ;; goal list carrier ;; agent carrying this agent (or "nobody") ] globals [ wolf goat cabbage man boat verbose? ;; if true, agents print what they are doing bank ;; location of river bank (+ or -) ] to setup clear-all set bank 13 set verbose? true ask patches with [ pxcor <= (- bank) or pxcor >= bank ] [set pcolor green ] ask patches with [ pxcor > (- bank) and pxcor < bank ] [set pcolor blue ] crt 5 [ setxy (bank + 3) 0 set speed 0.01 set size 3 set carrier nobody set goal [ ] ] set wolf (turtle 0) set goat (turtle 1) set cabbage (turtle 2) set man (turtle 3) set boat (turtle 4) let labels [ "wolf" "goat" "cabbage" "man" "boat" ] ask turtles [ set label (item who labels) ] ask man [ set shape "person" set size 4 set goal wgc-plan set color red ] ask cabbage [ set shape "plant" set carrier man set color 53 ] ask boat [ set size 5 set xcor (bank - 1) set speed (speed * 2) set color brown ] ask goat [ set shape "cow" set goal (list "eat" cabbage) set carrier man set color white ] ask wolf [ set shape "wolf" set goal (list "eat" goat) set carrier man set color black ] reset-ticks end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; NetLogo code for obeying instructions ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to obey if (carrier != nobody) [ move-to carrier ] if (goal != []) [ let kind (item 0 goal) if-else (kind = "goto") [ if (obey-goto (item 1 goal) (item 2 goal)) [ drop3-goal ] ] [ if-else (kind = "meet") [ if (obey-meet (item 1 goal)) [ drop2-goal ] ] [ if-else (kind = "eat") [ if (obey-eat (item 1 goal)) [ drop2-goal ] ] [ if-else (kind = "pickup") [ obey-pickup (item 1 goal) drop2-goal ] [ if-else (kind = "wait") [ if (runresult (item 1 goal)) [ drop2-goal ] ] [ if-else (kind = "drop") [ obey-drop (item 1 goal) drop2-goal ] [ if-else (kind = "instruct") [ obey-instruct (item 1 goal) (item 2 goal) drop3-goal ] [ if-else (kind = "go-left") [ obey-go-left ] [ if-else (kind = "go-right") [ obey-go-right ] [ if-else (kind = "embark") [ obey-embark drop-goal ] [ if-else (kind = "disembark") [ obey-disembark drop-goal ] [ obey-unknown kind ] ] ] ] ] ] ] ] ] ] ] ] end to drop-goal set goal (bf goal) end to drop2-goal set goal (bf (bf goal)) end to drop3-goal set goal (bf (bf (bf goal))) end to obey-unknown [ g ] show (list "unknown goal" g) drop-goal end to-report at-left report xcor = (1 - bank) end to-report at-right report xcor = (bank - 1) end to obey-go-left if (verbose?) [ show (list "going left") ] let g (list "goto" (1 - bank) 0) set goal (sentence (list "meet" boat "embark" "instruct" boat g "wait" (task at-left) "disembark" "goto" (- (bank + 3)) 0) (bf goal)) end to obey-go-right if (verbose?) [ show (list "going right") ] let g (list "goto" (bank - 1) 0) set goal (sentence (list "meet" boat "embark" "instruct" boat g "wait" (task at-right) "disembark" "goto" (bank + 3) 0) (bf goal)) end to obey-disembark if (verbose?) [ show (list "disembarking") ] set carrier nobody end to obey-embark if (verbose?) [ show (list "embarking") ] set carrier boat end to obey-pickup [ him ] ask him [ set carrier myself ] if (verbose?) [ show (list "picking up" ([label] of him)) ] end to obey-drop [ him ] if-else ([ carrier ] of him = self) [ ask him [ set carrier nobody ] if (verbose?) [ show (list "dropping" ([label] of him)) ] ] [ show (list "CANNOT DROP" ([label] of him)) ] end to obey-instruct [ him g ] if-else (g = []) [ ask him [ set goal [] ] ] [ ask him [ set goal (sentence goal g) ] ] if (verbose?) [ show (list "instructing" ([label] of him) "to" g) ] end to-report obey-goto [ x y ] ;; obey "goto x y" command; report true when achieved let d (distancexy x y) if-else (d = 0) [ if (verbose?) [ show (list "already at" x y) ] report true ] [ facexy x y if-else (d <= speed) [ setxy x y if (verbose?) [ show (list "have reached" x y) ] report true ] [ fd speed report false ] ] end to-report obey-meet [ him ] ;; obey "meet agent" command; report true when achieved if-else (him = self) [ if (verbose?) [ show (list "i am" him) ] report true ] [ face him let d (distance him) if-else (d <= speed) [ move-to him if (verbose?) [ show (list "have met" ([label] of him)) ] report true ] [ fd speed report false ] ] end to-report obey-eat [ him ] ;; obey "eat agent" command; report true when achieved if-else (carrier != nobody or distance him > 2 or ([ carrier ] of him) != nobody) [ report false ] [ face him let d (distance him) if-else (d <= speed) [ move-to him show (list "eating" ([label] of him)) ask him [ die ] report true ] [ fd speed report false ] ] end to go if (count (turtles with [ goal != []]) = 0) [ stop ] ask turtles [ obey ] tick end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; NetLogo code for planning ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; state format is [ w g c m ] ;; w = wolf, -1 for free on left, +1 for free on right, 0 for being carried ;; g = goat, c = cabbage, similarly ;; m = man, -1 for on left, +1 for on right to-report wgc-plan ;; top-level reporter to return the full plan let init-state [0 0 0 1] let p (planner init-state [] [] []) ;; add final entries to erase wolf and goat plans after the problem has been solved set p (sentence p (list "instruct" wolf [] "instruct" goat [])) show (fput "THE PLAN IS:" p) report p end to-report best-of [ x y ] ;; find the best of two solutions if-else (length x < length y and x != []) [ report x ] [ report y] end to-report acceptable [ state ] ;; everybody is on the left (possibly being carried) report ((item 0 state <= 0) and (item 1 state <= 0) and (item 2 state <= 0) and (item 3 state = -1)) end to-report bad [ state ] ;; wolf and goat loose together, or goat and cabbage loose together report ((item 0 state = -1 and item 1 state = -1) or (item 0 state = 1 and item 1 state = 1) or (item 1 state = -1 and item 2 state = -1) or (item 1 state = 1 and item 2 state = 1)) end to-report count-zeros [ x y z ] ;; count-zeros is used to count how much the man is carrying let n 0 if (x = 0) [ set n (n + 1) ] if (y = 0) [ set n (n + 1) ] if (z = 0) [ set n (n + 1) ] report n end to-report planner [ state history partial-solution best-so-far ] ;; the planner itself if-else ((bad state) or (member? state history) or (length best-so-far <= length partial-solution and best-so-far != [])) [ report best-so-far ] [ if-else (acceptable state) [ report best-of best-so-far partial-solution ] [ let h (lput state history) let b best-so-far let w (item 0 state) let g (item 1 state) let c (item 2 state) let m (item 3 state) ;; Can drop carried items on the current bank ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; if (item 0 state = 0) [ let s (list m g c m) let new-partial (sentence partial-solution (list "drop" wolf)) set b (planner s h new-partial b) ] if (item 1 state = 0) [ let s (list w m c m) let new-partial (sentence partial-solution (list "drop" goat)) set b (planner s h new-partial b) ] if (item 2 state = 0) [ let s (list w g m m) let new-partial (sentence partial-solution (list "drop" cabbage)) set b (planner s h new-partial b) ] ;; Can pick up items on the current bank ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; if (item 0 state = m) [ let s (list 0 g c m) let new-partial (sentence partial-solution (list "pickup" wolf)) set b (planner s h new-partial b) ] if (item 1 state = m) [ let s (list w 0 c m) let new-partial (sentence partial-solution (list "pickup" goat)) set b (planner s h new-partial b) ] if (item 2 state = m) [ let s (list w g 0 m) let new-partial (sentence partial-solution (list "pickup" cabbage)) set b (planner s h new-partial b) ] ;; Can go left or right if at most one item is being carried ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; if ((m = 1) and (count-zeros w g c <= 1)) [ let s (list w g c -1) let new-partial (sentence partial-solution [ "go-left" ]) set b (planner s h new-partial b) ] if ((m = -1) and (count-zeros w g c <= 1)) [ let s (list w g c 1) let new-partial (sentence partial-solution [ "go-right" ]) set b (planner s h new-partial b) ] report b ] ] end
There are 2 versions of this model.
Attached files
File | Type | Description | Last updated | |
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The wolf, the goat, and the cabbage.png | preview | Preview for 'The wolf, the goat, and the cabbage' | almost 11 years ago, by Anthony Dekker | Download |
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Anthony Dekker
Explanation
This model is associated with a tutorial at http://scientificgems.wordpress.com/2014/01/24/agent-goals-in-netlogo-the-wolf-the-goat-and-the-cabbage/
Posted almost 11 years ago
Anthony Dekker
Planning
The planning aspects of the model are discussed at http://scientificgems.wordpress.com/2014/01/25/planning-in-netlogo-the-wolf-the-goat-and-the-cabbage-again/
Posted almost 11 years ago
Anthony Dekker
Video
See https://vimeo.com/85013685 for a video of the program
Posted almost 11 years ago