turtles-own [man? woman? happy?]
patches-own [men women people]
globals [boring-groups moves number-happy group-sites]

to setup
  ca
  set group-sites patches with [group-site?]
  set-default-shape turtles "person"
  cct number [
    ;;blue represents male, pink represents female. No stereotypes are meant
    ;;to be promoted. Simply change the colors right here if you'd like.
    ifelse (random 2 = 0)
       [set man? true set woman? false set color blue] 
       [set man? false set woman? true set color pink]
    ifelse (random 2 = 0) [set heading 90] [set heading 270] ;; randomly face right or left
    set ycor 0
    set xcor random screen-size-x ]
  ask turtles
    [move-into-groups]
  setup-patches
  setup-plots
  set moves 0
  update-labels
  spread-people 
  update-plots
end

to setup-patches
  ask patches [
    set men 0
    set women 0
    set people 0]
  ask turtles [
    if man? [set men (men + 1)]
    if woman? [set women (women + 1)]]
  ask patches [
    set people (men + women)]
  update-happiness
  update-boring-groups
end

to go
  if (number-happy = number)
  [
    stop   ;; stop the simulation if everyone is happy
  ] 
  group-people ;; put all people on the x-axis
  update-happiness
  move-if-unhappy  
  update-boring-groups
  update-labels
  spread-people ;; move the people into vertical columns
  set moves (moves + 1)
  update-plots
  if limit-speed?
    [ wait 0.75 ] ;; keep the spread groups on the screen for a bit
end

to update-labels
  ask group-sites
    [ set plabel count turtles-here ]
end

to update-happiness
  ask patches [
    set people (men + women)]
  ask turtles [   ;;; you are happy if the proportion of people of the opposite sex does not exceed your tolerance
    if man? [ifelse (women / people) > (tolerance / 100)
              [set happy? false]
              [set happy? true]]
    if woman? [ifelse (men / people) > (tolerance / 100)
            [set happy? false]
            [set happy? true]]
   ;; if (happy? = true) [set num-happy (num-happy + 1)]
   ] 
  set number-happy count turtles with [happy?]  ;; update number-happy variable
end

to move-if-unhappy
  ask turtles [
    if (not happy?)
      [ifelse man? [set men men - 1]   ;;decrease the count in your old group
                   [set women women - 1]
       ifelse (random 2 = 0) [set heading 90] [set heading 270] ;; randomly face right or left
       fd 1  ;; move out of your group
       move-into-groups
       ifelse man? [set men men + 1] [set women women + 1]]] ;;increase the count in your new in group
end

to move-into-groups  ;;turtle procedure
  ; move forward until you hit the closest group
 if not group-site?
   [ fd 1
     if limit-speed?
       [ wait 0.1 ] ;; slow it down so user can see it happening
     move-into-groups]
end

to-report group-site?  ;; turtle or patch procedure
  ;; if your pycor is 0 and your pxcor is where a group should be located,
  ;; then you're a group site (patch) or on a group site (turtle)
  locals [group-interval]
  ;; first figure out how many patches apart the groups will be
  set group-interval floor (screen-size-x / num-groups)
  report
    ;; first check pycor
    (pycor = 0) and
    ;; then check if the distance between groups divides evenly into
    ;; our distance from the right hand edge of the screen
    (((screen-edge-x - pxcor) mod group-interval) = 0) and
    ;; finally, make sure we don't wind up with more groups than
    ;; the user asked for
    (floor ((screen-edge-x - pxcor) / group-interval) < num-groups)
end

to update-boring-groups
  ask group-sites [
    set plabel-color white
    if people > 0
      [if ((men = 0) or (women = 0)) [set plabel-color gray]]]
  set boring-groups (count group-sites with [plabel-color = gray])
end

to setup-plots
  set-current-plot "Happy Partygoers"
  set-plot-y-range 0 number
end

to update-plots
  set-current-plot "Happy Partygoers"
  set-current-plot-pen "Happy"
  plot (count turtles with [happy?]) 
  set-current-plot "Single Sex Groups"
  plot boring-groups
end

;; spread people out vertically 
to spread-people
  ask turtles [ifelse man?
                [set heading 0 fd 2]
                [set heading 180 fd 2]
  jump count other-turtles-here] ;; this trick works because of the serial ordering of turtle execution
end
  
;; pile people up on the x-axis                           
to group-people
  ask turtles [set ycor 0]
end


; *** NetLogo Model Copyright Notice ***
;
; This model was created as part of the project: CONNECTED MATHEMATICS:
; MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECT-BASED PARALLEL
; MODELS (OBPML).  The project gratefully acknowledges the support of the
; National Science Foundation (Applications of Advanced Technologies
; Program) -- grant numbers RED #9552950 and REC #9632612.
;
; Copyright 1997 by Uri Wilensky. All rights reserved.
;
; Permission to use, modify or redistribute this model is hereby granted,
; provided that both of the following requirements are followed:
; a) this copyright notice is included.
; b) this model will not be redistributed for profit without permission
;    from Uri Wilensky.
; Contact Uri Wilensky for appropriate licenses for redistribution for
; profit.
;
; This model was converted to NetLogo as part of the project:
; PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN
; CLASSROOMS.  The project gratefully acknowledges the support of the
; National Science Foundation (REPP program) -- grant number REC #9814682.
; Converted from StarLogoT to NetLogo, 2001.  Updated 2002.
;
; To refer to this model in academic publications, please use:
; Wilensky, U. (1997).  NetLogo Party model.
; http://ccl.northwestern.edu/netlogo/models/Party.
; Center for Connected Learning and Computer-Based Modeling,
; Northwestern University, Evanston, IL.
;
; In other publications, please use:
; Copyright 1998 by Uri Wilensky.  All rights reserved.  See
; http://ccl.northwestern.edu/netlogo/models/Party
; for terms of use.
;
; *** End of NetLogo Model Copyright Notice ***
@#$#@#$#@
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WHAT IS IT?
-----------
This program models a cocktail party.  The party is made up of groups of both men and women.  The partygoers have a TOLERANCE that defines their comfort level with a group that has members of the opposite sex.  If they are in a group that has a higher percentage of people of the opposite sex than their TOLERANCE allows, then they are considered "uncomfortable", and they leave that group to find another group.  This action continues until everyone at the party is "comfortable" within their group.

This model is based on the work of the pioneering economist Thomas Schelling. It is also described in: Resnick, M. & Wilensky, U. (1998). Diving into Complexity: Developing Probabilistic Decentralized Thinking through Role-Playing Activities. Journal of Learning Sciences, Vol. 7, No. 2. http://ccl.northwestern.edu/cm/papers/starpeople/


HOW TO USE IT
-------------
To set the number of people at the party, use the NUMBER slider. 

To set the number of initial groups, use the NUM-GROUPS slider.

To set the tolerance of the people for the opposite sex, use the TOLERANCE slider.  If the TOLERANCE slider is set to 75, then each person will tolerate being in a group with less than or equal to 75% people of the opposite sex.  If there are more than this, the person is uncomfortable, and he/she leaves the group and tries out an adjacent group.

The SETUP button sets up all the people into random groups.  The GO button sets the party in motion. You can use the STEP-ONCE button to make all uncomfortable partygoers move once.  The MOVES monitor shows the number of times people move from their groups. The NUMBER-HAPPY monitor shows how many people are content and this value is dynamically graphed in the "happy partygoers" plot. The counts are shown in gray for "single-sex" groups, white for mixed groups.  The simulation ends when everyone is happy.  The SINGLE-SEX-GROUPS monitor shows the number of single-sex groups and this value is dynamically plotted in the "single sex groups" plot.


RUNNING the MODEL
-----------------

THINGS TO NOTICE
----------------
At the end of the simulation (when everyone is happy), notice the number of single-sex groups.  Is there an increase from their initial compositions?

Is there a critical tolerance at which each group ends up being a single-sex group?

Notice the difference in time it takes for all groups to be comfortable depending upon the tolerance.


THINGS TO TRY
-------------
See how many mixed groups (not a single-sex group) you can get.
  
Use the STEP-ONCE button, and experiment with different tolerances.  Watch how one unhappy person can disrupt the stability of other groups.

Is it possible to have an initial grouping such that the party is never completely content? (i.e. the model never terminates)

Observe real parties. Is this model descriptive of real social settings?  What tolerances would model the people in the real party?


EXTENDING THE MODEL
-------------------
Add another dimension to the model.  Instead of male/female, try a trait that has more than two types, like race or religion. You can use BREEDS to implement that.

Allow each BREED of person to have their own tolerance.

Complicate the tolerance rules: For example, the tolerance could go up as long as there are at least 2 of one BREED.

Allow groups to subdivide, instead of finding new groups.

Set a maximum group size, so that if there are too many people in the group, they become unhappy.


NETLOGO FEATURES
-----------------
Notice the use of the "mod" function with a portion of the "screen-size" to space out the groups evenly. Setting up the groups in this manner allows for easy movement from group to group.

Note also the use of the seriality of turtle execution for spreading out the turtles. Knowing that lower numbered turtles execute first enables this code to align the labels in the SHOW-COUNTS option.


RELATED MODELS
---------------
Segregation


CREDITS AND REFERENCES
----------------------
Schelling, T. (1978). Micro-motives and Macro-Behavior. New York: Norton. 

Resnick, M. & Wilensky, U. (1998). Diving into Complexity: Developing Probabilistic Decentralized Thinking through Role-Playing Activities. Journal of Learning Sciences, Vol. 7, No. 2.

To refer to this model in academic publications, please use: Wilensky, U. (1997).  NetLogo Party model. http://ccl.northwestern.edu/netlogo/models/Party. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

In other publications, please use: Copyright 1997 by Uri Wilensky.  All rights reserved.  See http://ccl.northwestern.edu/netlogo/models/Party for terms of use.
@#$#@#$#@
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NetLogo 2.0alpha2
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