I am not sure how netlogo processes commands. Consider the following scenario. There are 100 turtles. The "go" procedure calls the following other procedures: A, B, and C. Procedure A tells turtles to do some things, Procedure B tells turtles to do some things, and Procedure C tells turtles to do some things.
Understanding X:
It is my understanding that all turtles would complete the commands in A, then all turtles would complete the commands in B, then all turtles would complete the commands in C.
Now, inside procedure A there are commands A1, A2, and A3.
Understanding Y:
It was my understanding that, inside procedure A, one turtle would do command A1, then A2, then A3, then a second turtle would do command A1, A2, and A3, and so on.
Is my understanding Y correct?
Thanks for any insights you can provide.
It depends. The basic rules is that the user presses the go button (or types 'go' in the command center) and that tells NetLogo to run the go procedure. NetLogo runs that procedure from top to bottom. But how you include the called procedures changes the order.
Consider version 1. The first line ask turtles says to choose a random turtle, make it do everything in the code block (delimited by the [ ] symbols) and then choose the next random turtle, make it do everything and then the next turtle until all the turtles are done. In this case, both proc-A and proc-B are within the same code block, so the turtle would do both before NetLogo switches to the next turtle.
to go
ask turtles
[ proc-A
proc-B
]
end
to proc-A
forward 1
set heading heading + random 10
end
to proc-B
forward 3
set heading heading - random 20
end
How about version 2? The first line ask turtles [proc-A] says to choose a random turtle, make it do everything in the code block (delimited by the [ ] symbols) which in this case is only proc-A. And then choose the next random turtle, make it do everything and then the next turtle until all the turtles are done. Only after ALL the turtles are done with the ask turtles will the code move on to the next line. In this case therefore, all turtles do proc-A and then all turtles do proc-B.
to go
ask turtles [ proc-A ]
ask turtles [ proc-B ]
end
to proc-A
forward 1
set heading heading + random 10
end
to proc-B
forward 3
set heading heading - random 20
end
You could also do something like version 3. The first line says to run through proc-A, which gets every turtle to do something. Then, at the end of proc-A, control returns to the go procedure and moves to the next line, which is to run the procedure proc-B. This would achieve the same outcome as version 2.
to go
proc-A
proc-B
end
to proc-A
ask turtles
[ forward 1
set heading heading + random 10
]
end
to proc-B
ask turtles
[ forward 3
set heading heading - random 20
]
end
When I am teaching NetLogo, I encourage my students to construct the code along the lines of version 3. This is because the ask is within the same procedure as the actions they are being asked to do. This has several advantages. (1) Much easier to read because you don't have to try and read across procedures that could be a long way apart. (2) Avoids one of the most common beginner issues of nested ask - with an ask turtles in the go procedure and then ask turtles again as the first line of the called procedure. This is actually such a common bug that the NetLogo developers have made it impossible to have nested asks.
However, if you truly want a turtle to do more than one thing before the next turtle starts, then you have two options. You either code as in version 1. Or you put both things that you want the turtle to do in the same procedure.
Related
Picture of my behaviourspace menu
I'm working on an agent based model where a variable (agentvariable1) owned by all agents changes every tick. I want to report a time series for the values of this variable for every agent using Behaviourspace.
However, when I measure runs using the following reporter
[agentvariable1] of turtles
the values that are reported for agentvariable1 are randomly shuffled, because "turtles" calls all turtles in a random order, which is different every tick. Because of this the data that is exported is not usable to create a time-series.
Is it posstible to create a reporter in Behaviourspace that reports the values of the agentvariable1 in a sequence that remains the same every tick?
Using sort on an agentset creates a list of those agents sorting them by some criteria. In the case of turtles, they are sorted by their who which means that their relative order will always be the same.
However you cannot directly do [agentvariable1] of sort turtles, because of expects an agent/agentset but you are giving it a list.
What you can do is creating a global variable as a list: at each tick the list is emptied, and later all turtles (sorted as per sort) will append their value to the list.
That list is what you will report in your Behavior Space.
globals [
all-values
]
turtles-own [
my-value
]
to setup
clear-all
reset-ticks
create-turtles 5
end
to go
set all-values (list)
ask turtles [
set my-value random 10
]
foreach sort turtles [
t ->
ask t [
set all-values lput my-value all-values
]
]
show all-values
tick
end
As an alternative to Matteo's answer (which is perfectly suitable and directly addresses your intention, I just present another option depending on preference) you could also pair the variable of interest with some turtle identifier and report that as a list of lists. This adds a bit of flexibility in cases where the number of turtles increases or decreases. In this example, I use who and xcor for simplicity, but you may want to create your own unique turtle identifier for more explicit tracking. With this toy model:
to setup
ca
crt 5
reset-ticks
end
to go
ask turtles [
rt random 30 - 15
fd 1
]
tick
end
to-report report-who-x
report list who xcor
end
At any point, you can call the list with [report-who-x] of turtles to get a list of lists. With a behaviorspace setup such as:
you get an output that would look something like:
I have one doubt:
Context: I have a code in which, briefly, turtles have an integer variable (energy-collected) and from that, patches update their own variable (energy-of-my-agent), as described in the code snippet below.
Problem: The turtle variable is of type int (-1, for example), but the patch variable is a one-element list ( [-1] ).
Question: Should this happen? Otherwise, how can I make the patch variable just an integer value?
ask turtles
[
set energy-collected (energy - euse)
]
ask patches
[
set energy-of-my-agent [energy-collected] of turtles-here
]
Thanks in advance
The main thing you have to consider is what of reports.
In your case turtles-here is an agentset, not a specific agent.
This is because, although you might have a single turtle on a patch, you may also have multiple turtles on a patch. Therefore turtles-here reports an agentset, even if that agentset may be made of a single turtle.
It follows that a collection of values from an agentset, obtained with of (and [energy-collected] of turtles-here is exactly that), will be a list of values - even if that list contains only one element.
Therefore I would say:
Is your model made in such a way that each patch cannot have more than one turtle at a time? Then you could do:
ask patches [
if any? turtles-here [
set energy-of-my-agent [energy-collected] of one-of turtles-here
]
]
In the code above, one-of turtles-here reports a specific agent - not an agentset anymore.
So its variable's value, obtained with of, will be stored as a single value (provided that the agent's variable is not a list itself, but that's not your case).
Can it happen that your patches have more than one turtle at a time? Then, if you're interested in the single patch holding "its" turtles' values, dealing with lists is probably necessary.
Update
I made a connection between this question and your other one suggesting that you want to use patches as elements of matrices.
Maybe this is useful to your case: if your model allows for the possibility of having more than one turtle on the same patch, you might be interested in doing something like:
ask patches [
set energy-of-my-agent sum [energy-collected] of turtles-here
]
As you can see, sum takes a list as input and reports a number. Each patch will take the sum of all the values of energy-collected by turtles standing there, or you can change the calculation using whatever you want (e.g. mean, max etc).
Actually, you can use this approach regardless: this way, even when you have a single turtle on a patch, sum (or any other function taking a lost and returning a value) will give you a single value where before you had a list of one value.
I would like to apply some process stochastically, but the order matters, or rather it should be done at random, how can I select a set of the same turtles to "treat" but to do it such that each tick, the order is random?
ask turtles [
;; apply a process to turtles, but not all turtles will get something as the pool of energy may have run out by the time they are selected.
]
Elements of agentsets (such as turtles) are always returned in a random order. Each time you use ask with an agentset, it will ask them in a new, random order. From the docs on agentsets:
An agentset is not in any particular order. In fact, it’s always in a random order. And every time you use it, the agentset is in a different random order. This helps you keep your model from treating any particular turtles, patches or links differently from any others (unless you want them to be). Since the order is random every time, no one agent always gets to go first.
And here is a quick example to demonstrate. If you run it in the Command Center you'll see the who numbers will be different each time you ask them to be shown.
to test
clear-all
create-turtles 10
show "Asking once..."
ask turtles [ show who ]
show "Asking a second time..."
ask turtles [ show who ]
end
And here is an example showing an energy pool that will be randomly used until it is gone. Note the turtles that will get to use it are whichever happen to come first out of the agentset for ask:
to test-pool
clear-all
let energy-pool 1000
create-turtles 100
ask turtles [
; can only act if some energy is left...
ifelse energy-pool > 0 [
let energy-use (min (list random 100 energy-pool))
set energy-pool (energy-pool - energy-use)
show (word "I used up " energy-use " energy points! " who " Only " energy-pool " points left")
] [
show (word "No energy left for me! " who)
]
]
end
I have two procedures (Levy Walk and Correlated Random Walk movement strategies, each with their own buttons for debugging purposes, as well as their own parameter sets on the netlogo interface), but I have also embedded both the aforementioned procedures in a single "Go" procedure for batch simulation processing in the following code implementation:
to setup
clear-all
create-turtles 100 [ setxy random-xcor random-ycor ]
reset-ticks
end
to Correlated-Random-Walk
rt random 360
fd 1
end
to Levy-Walk
rt random 90
fd 2
end
to go
Correlated-Random-Walk
tick
if ticks = 1000 [
setup
stop
Levy-Walk
if ticks = 1000 [
setup
stop
]
]
end
The above section of the "Go" procedure code is supposed to take the correlated random walk procedure and execute it for the entire duration (1000 ticks) of the simulation, then stop, reset (setup) the world and execute the levy walk procedure to the entire duration of the simulation (also a 100 ticks), then stop. As it is now, the code executes for the correlated random walk but does not go on to the levy walk procedure. It simply repeats the Correlated Random Walk procedure. What might the issue be?
Your stop command will stop the go procedure. (See the docs.) Does the following meet your needs?
to go1000each
repeat 1000 [Correlated-Random-Walk tick]
setup
repeat 1000 [Levy-Walk tick]
end
If you make a button for this, it should not be a forever button.
In NetLogo: suppose the model has
a turtle (0) of breed A with undirected links with 3 turtles (1, 2 and 3) of breed B;
the turtle 0 has an attribute named "number-of-links" that equals 3.
Now, let one of the 3 neighbors of 0 dies..
How can I program turtle 0 to change its number-of-links automatically to 2?
If all you want is a way of keeping track of the number links, use count my-links instead of a custom variable.
In general, the least bug prone way of having a value update when the number of links changes is to compute that value when you need it. For number of links, this is simply count my-links. For more complicated things, wrap them in a reporter:
to-report energy-of-neighbors
report sum [ energy ] of link-neighbors
end
If this doesn't work for whatever reason (agents need to react to a link disappearing or you're seeing a serious, measurable performance hit from calculating on the fly), you'll have to make the updates yourself when the number of links change. The best way to do this is to encapsulate the behavior in a command:
to update-on-link-change [ link-being-removed ] ;; turtle procedure
; update stuff
end
and then encapsulate the things that can cause the number of links to change (such as turtle death) in commands as well:
to linked-agent-death ;; turtle procedure
ask links [
ask other-end [ update-on-link-change myself ]
]
die
end