I am trying to simulate the Mt/M/c queueing model in Anylogic. I want the Source to generate agent by a Non Homogenous Poisson Process, which requires the arrival rate function to be like, for example, a+b*sin(t). However, I found that the source can only generate by fixed rate or rate schedule.
I am wondering if there is some way to generate agents by the rate function given in Anylogic.
Sure, set the Source to "create agents by call of inject()" method:
Then, create a DynamicEvent with the action code as below. This will inject 1 agent at the specified interval from your equation:
Last, you need to "seed" this setup by calling create_MyDynamicEvent(0, SECOND) once on startup of Main (to make the dynamic event re-call itself from then onwards)
Related
I am currently completing some verification checks on an Anylogic DES simulation model, and I have two source blocks with identical hourly arrival rate schedules, broken down into 24 x 1h blocks.
The issue I am encountering is significant differences in the number of agents generated by one block compared with another. I understand that the arrival rate is based on the poisson distribution, so there is some level of randomness in the instants of agent generation, but I would expect that the overall number generated by these two blocks should be similar, if not identical. For example, in one operating scenario one block is generating 78 agents, whilst the other is only generating 67 over the 24h period. This seems to be a common issue across all operating scenarios.
Is there a potential explanation regarding idiosyncrasies within Anylogic that might explain this?
Any pointers would be welcomed.
I think it occurs because it follows a poisson distribution. To solve this, you could use the interarrival time function of the source block. In that case you would have the same number of arrivals for different source blocks. However, I'm not sure whether this fits a schedule. If not, you could use the getHourOfDay() function together with a parameter representing the interarrival time. You then have to write the code below for every hour of the day:
if(getHourOfDay()==14) parameter =5;
using sources with poisson distributions will definitely not produce same results... That's the magic of stocastic models.
An alternative to solve this problem is the following:
sources will generate using the inject function
use dynamic events that will be in charge to do source.inject();
let's imagine you have R trains coming per day, and this is a fixed value you want to use, you can then distribute the trains accross the day by doing this:
for(int i=0;i<R;i++){
create_DynamicEvent1(uniform(0,1),DAY); //for source1
create_DynamicEvent2(uniform(0,1),DAY); //for source2
}
This doesn't follow a poisson distribution, but generates a predefined number of arrivals of trains throughout the day, and you can use another distribution of your choice if the uniform is not good enough for you.
run this for every day
I have a model that I have duplicated and made some adjustments to it. When I run both models with the same fixed seed I don’t get the same results, which I understand because I have other sources of randomness in the model. Regardless, in both models, I am using a source block, such that the arrivals are defined by a rate schedule, the schedule is of type rate, and is provided from the database. Now, I know the following pieces of information:
Generally, I can use my own random number generator (RNG) in distributions, for example triangular(5, 10, 25, myRNG), such that Random myRNG = new Random (2)
By default, a schedule with “type” rate follows a passion distribution that utilizes the default RNG.
At anytime in the model, I can substitute the default RNG with my own by calling setDefaultRandomGenerator(Random r).
The question is: Is it possible to use a fixed seed for the arrival rate to make sure I am getting the same exact input in both models?
In anylogic, rates are always equivalent to a poisson distribution with lambda equal to the rate you set,
Intearrival times don't follow any distribution, but using exponential(lambda) in the field is equivalent to using a arrival by rate with a rate of lambda.
But poisson and exponential are closely related, which is why if you use poisson(1.0/lambda) in the intearrival time, you have the same average arrivals as if you use exponential(lambda).
It is not possible to set a seed for the arrival rate, and that's why you need to use intearrival times instead in your source
But you need to create a variable first, let's call it rand, of type Random with initial value new Random(seed)
where seed is any integer you want (long to be more exact)
then in the intearrival time you need to do:
exponential(lambda, 0,rand)
This will lead to unique simulation runs, no matter what configuration you have in the AnyLogic experiment
Sure, simply set both Source blocks to "Interarrival time" in the "arrivals defined by".
Then, use the same code poisson(1, myRNG) in the field, making sure that the myRNG RNG uses the same initial seed (i.e.new Random(1234)
(the "Rate" setting is the same as using poission(1) for interarrival-time)
I am trying to simulate a finite calling population model in AnyLogic. My population consists of 10 agents and I want them to come back to the Source node after they have been served.
I thought about making conditioning with the SelectOutput node but the Source node does not have any input. The best thing that I came up with is to just limit the number of customers arrivals to 10. However, in this case, the model stops running after 10 arrivals which is not an appropriate result.
What can I do to be able to simulate such a type of model in AnyLogic?
EDIT: I thought that making agents come back to the Source node could be a solution to building the finite calling population model. The main purpose of my question is to understand how can I build such type of model in AnyLogic. Here is the description of the concept of the model.
You cannot send them back to a Source element, as it only acts to create agents.
However, you can send them back to blocks that come after the source as below:
Here, all agents created by the Source block will infinitely loop through the Queue and Delay blocks.
I would like to analyse the electrical energy consumed by a furnace in a conveyor system. Is there a method or specific function to do this using Anylogic?
I've found little material surrounding this, so pointing in the right direction would be great.
Simple answer: There is no build-in functionality. But you can easily do this yourself.
If you want very high accuracy, you should check system dynamics (but this slows your model quite a bit).
If you want a simple approach, I can think of this:
create a variable elecConsumptionPerMin in your furnace agent
create an event consumeElec in your furnace that cyclically (every minute) adds to the total furnace consumption (another variable)
on model startup, ideally set myFurnace.consumeElec.suspend()
when the furnace starts producing, call ´myFurnace.consumeElec.resume()` to start consuming enegery
Obviously, you can refine this to the nth degree and you might also want to experiment with state charts. But this is the simple approach
I have two model references - Slow model and Fast model, each running at its own rate for concurrent execution on the grt "generic real time" . However when I attempt to build the block I get the following error:
Simulink cannot generate code for the signal at output port 1 of block
'Multirate/Fast' because the signal requires data transfer that
generates lock-free code for a rate monotonically scheduled task.
I am not sure what to configure in simulink to overcome this error. I attempted to add rate transition from the Fast model to the Slow model but the error remains.
Any thoughts
Since there are many possibilites I can't give you a simple answer but you can try the following:
Check if simulink can determine your sample rates... Did you configure that correctly (go to view and set sample rate colors) then you see if Simulink detects the execution times correctly.
If your Simulink Block ('Fast') is contained in a single subsystem make it an atomic subsystem... an configure the sample rate on the subsystem properties.
Set the strictest constrains in the rate transition block...
How is your Model configuration? is it set to multitaskig....