Modeling the Spread of Viral Videos

extensions [ nw ]
globals [
  ;;from http://link.springer.com.turing.library.northwestern.edu/article/10.1007/s10844-011-0191-2/fulltext.html\
  ;;rates of likelihood of sharing based on type of video
  likelihood-list

  ;;Possible types of video
  types-of-video

  ;most popular video
  most-popular-video

  ;most sharing person
  most-sharing-person

  ;total number of videos that have been shared
  total-number-shared

  ;rates of sharing by video-type found by model
  rates-of-sharing

  types-of-social-motivation
]

turtles-own [
  ;; videos this turtle has seen (will have video-ids of patches)
  videos-seen
  ;; chance that this person will share
  chance-of-sharing
  ;; if you are recommending right now
  recommending?
  ;previous recommender
  prev-recommender
  ;number of times this person has shared a video
  num-times-shared
]
patches-own [
  ;; number of times video has been viewed
  num-times-viewed
  ;; type of video
  video-type
  ;; id for videos to be put into "videos-seen" of turtles
  video-id
  ;social motivation ratings
  motivation-ratings

  ;last person who shared this video
  shared-by

]

links-own [
  weight
]

to setup
  clear-all
  set-globals
  create-people
  create-all-videos
  reset-ticks
end 

to set-globals
  ;;from http://link.springer.com.turing.library.northwestern.edu/article/10.1007/s10844-011-0191-2/fulltext.html\
  ;;rates of likelihood of sharing based on type of video

   set likelihood-list [42.3 38.8 31.7 29.5 28.8 28.4 28.1 26.7 23.8 20.0 19.7 15.6 15.3 14.0 12.8 9.8]

   set types-of-social-motivation ["shared-passion" "social-irl" "social-utility" "social-good" "zeitgeist" "kudos" "reaction-seeking" "self-expression" "shared-emotional-experience"]

   set rates-of-sharing [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

   ;;possible types of video
   set types-of-video [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16]

   set most-popular-video max-one-of patches [num-times-viewed]

   set most-sharing-person max-one-of turtles [num-times-shared]

   set total-number-shared 1
end 

to create-people
  set-default-shape turtles "person"
  if network-type = "random" [ create-random-network ]
  if network-type = "preferential" [ create-preferential-network ]
  if network-type = "small-world" [ create-small-world-network ]
  setup-links

  ask turtles [
    ;nobody has recommended a video yet
    set prev-recommender nobody

    set color brown + 1

    ;;nobody has seen any videos at the start
    set videos-seen []

    ;how often this turtle shares a video they like
    set chance-of-sharing random 100

    ;no turtle is recommending a video upon initialization
    set recommending? false

    ;;random x y position
    setxy random-xcor random-ycor
  ]
end 

;creates a random network between turtles

to create-random-network
  ; with 10% chance of being connected
  nw:generate-random turtles links number-of-people 0.1
end 

to create-preferential-network
  nw:generate-preferential-attachment turtles links number-of-people
end 

to create-small-world-network
  let sq sqrt number-of-people
  nw:generate-small-world turtles links sq sq 2.0 false
end 

to setup-links ;link procedure
  ask links [
    set weight 1
    set label weight
  ]
end 

to create-new-video ;patch procedure
  set num-times-viewed 0

  set shared-by nobody

  set motivation-ratings (list (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) (random 5 + 1) )

  ;going from upper-left corner to bottom right corner
  if pxcor <= -8 and pxcor >= -16 and pycor <= 16 and pycor >= 8 [ set video-type 1 ]
  if pxcor <= -8 and pxcor >= -16 and pycor <= 8 and pycor >= 0 [ set video-type 2 ]
  if pxcor <= 0 and pxcor >= -8 and pycor <= 16 and pycor >= 8 [ set video-type 3 ]
  if pxcor <= -8 and pxcor >= -16 and pycor <= 0 and pycor >= -8 [ set video-type 4 ]
  if pxcor <= 0 and pxcor >= -8 and pycor <= 8 and pycor >= 0 [ set video-type 5 ]
  if pxcor <= 8 and pxcor >= 0 and pycor <= 16 and pycor >= 8 [ set video-type 6 ]
  if pxcor <= -8 and pxcor >= -16 and pycor <= -8 and pycor >= -16 [ set video-type 7 ]
  if pxcor <= 0 and pxcor >= -8 and pycor <= 0 and pycor >= -8 [ set video-type 8 ]
  if pxcor <= 8 and pxcor >= 0 and pycor <= 8 and pycor >= 0 [ set video-type 9 ]
  if pxcor <= 16 and pxcor >= 8 and pycor <= 16 and pycor >= 8 [ set video-type 10 ]
  if pxcor <= 0 and pxcor >= -8 and pycor <= -8 and pycor >= -16 [ set video-type 11 ]
  if pxcor <= 8 and pxcor >= 0 and pycor <= 0 and pycor >= -8 [ set video-type 12 ]
  if pxcor <= 16 and pxcor >= 8 and pycor <= 8 and pycor >= 0 [ set video-type 13 ]
  if pxcor <= 8 and pxcor >= 0 and pycor <= -8 and pycor >= -16 [ set video-type 14 ]
  if pxcor <= 16 and pxcor >= 8 and pycor <= 0 and pycor >= -8 [ set video-type 15 ]
  if pxcor <= 16 and pxcor >= 8 and pycor <= -8 and pycor >= -16 [ set video-type 16 ]
  set pcolor video-color? video-type
end 

to create-all-videos ;patch procedure
  ask patches [ create-new-video ]
  ;;create unique id for each patch
  (foreach (sort patches) (n-values count patches [?]) [ ask ?1 [ set video-id ?2 ] ])
end 

to go
  ask turtles [
    watch-video
    find-new-video
  ]
  ; every deletion-rate number of ticks, delete old videos with too little views
  if ticks mod deletion-rate = 0 [
    check-if-delete-video
  ]

  ;update MPV variable
  set most-popular-video max-one-of patches [num-times-viewed]

  ;update MSP variable
  set most-sharing-person max-one-of turtles [num-times-shared]

  tick
end 

to watch-video ;turtle procedure
  set recommending? false
  let video [video-id] of patch-here
  ;if you've seen it, only a 50% chance you'll see it again. Otherwise, move to a related video
  ifelse member? video videos-seen and random 10 < 5 [
     rt random 360
     fd 1
  ] [
    ask patch-here [
      ;set patch's own num-times-viewed
      set num-times-viewed num-times-viewed + 1
       ;change color every 5 views
       if num-times-viewed mod 5 = 0 [
         ifelse pcolor mod 10 = 0 [ set pcolor 0 ] [ set pcolor pcolor - 0.1 ]
       ]
     ]
    set videos-seen lput video videos-seen
    calculate-chance-of-sharing
  ]
end 

to calculate-chance-of-sharing ;turtle procedure
  let temp-likelihood 0
  let index video-type - 1
  set temp-likelihood item index likelihood-list
  let social-motivation-rate [mean motivation-ratings] of patch-here / 5 ;5 because maximum motivation rating is a 5 for each of 9 categories, find that mean
  ; if product of them sharing it and likelihood of video type being shared is enough, share it
  if random-float 1 <  social-motivation-rate * (chance-of-sharing / 100) * (temp-likelihood / 100) [
    set shared-by self
    share-video index
    ;you liked and shared the video your previous recommender recommended
    ;strengthen the connection between you two
    if prev-recommender != nobody [
      ask link-with prev-recommender [
        set weight weight + 1
        set label weight
      ]
    ]
  ]
end 

to share-video [index] ;turtle procedure
  set num-times-shared num-times-shared + 1

  ;set total times shared
  set total-number-shared total-number-shared + 1

  ;set total times this video type has been shared
  let temp-val item index rates-of-sharing
  set temp-val temp-val + 1
  set rates-of-sharing replace-item index rates-of-sharing temp-val

  set recommending? true
end 

to find-new-video ;turtle procedure
  let links-sharing my-links with [[recommending?] of other-end]

  ; if anyone is currently sharing
  if any? links-sharing [
    let bff-whos-sharing [other-end] of max-one-of links-sharing [weight]

    ;let bff-whos-sharing [other-end] of max-one-of my-links with [[recommending?] of other-end] [weight]
    if bff-whos-sharing = nobody [ stop ]

    set prev-recommender bff-whos-sharing

    move-to [patch-here] of bff-whos-sharing
  ]
end 

to check-if-delete-video ;patches procedure
  ;will let us know whether to delete video-id from turtles' videos-seen list
  let deleted-videos []
  ask patches [
    let most-viewed [num-times-viewed] of most-popular-video
    ;create a new video in its place
    if random 100 < chance-of-deletion [
      set deleted-videos lput video-id deleted-videos
      create-new-video
    ]
  ]
  ;remove the deleted videos from the turtles "video-seen" list because now
  ;new videos have taken their place
  foreach deleted-videos [
    ask turtles [
      if member? ? videos-seen [
        set videos-seen remove ? videos-seen
      ]
    ]
  ]
end 

to-report video-color? [v-type]
  let dark-gray gray - 3
  let color-list (list red orange brown yellow green lime turquoise cyan sky blue violet magenta pink gray dark-gray white)

  let index v-type - 1
  report item index color-list
end 

to-report nominal-video-type? [v-type]
  let type-list ["Animals" "Activism" "Politics" "Travel" "Education" "Science" "Sports" "People" "Autos" "Comedy" "Howto" "Entertainment" "Games" "Film" "Music" "Shows"]
  let index v-type - 1
  report item index type-list
end