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Hi Mike,
I am thrilled with this discussion!.
I am sorry that I might have led to
misunderstanding, it could be because english is not my native
language.
What I meant with "alive at the same tick" is that
one class of agent can instantiate many agents (objects).
And I do not know how to make two or more agents
(instances) of the same class of agent have their task run at different
processors (or threads) at the same time with the Scheduler.
What I understood is that in the same tick, the
agents array is read and the step() method of each agent is ran in random or
determined order. The step method of each agent is synchronous.
And for "threaded agent task" I meant that a step()
method of an agent could run indefinetly until a pause, stop or end event is
triggered by the command bar.
Sorry to make this discussion a lecture but it is
really important for my research to get this issue thorougly
cleared.
Thanks Mike and Marcus,
PS: I promisse to send a translated paper to you
both!
----- Original Message -----
Sent: Wednesday, August 31, 2005 8:38
PM
Subject: RE: [Swarm-Modelling] True
Concurrency?
The answer depends on
what threaded agent tasks and alive at the same tick mean. If
these phrases mean that the code for two different agents executes at the same
physical moment on two different processors (with shared memory) then Repast
can do this.
Mike
From: address@hidden
[mailto:address@hidden On
Behalf Of Valmir Meneses
Sent: Wednesday, August 31, 2005 2:20
PM
To: address@hidden
Cc: Swarm
Modelling
Subject: [Swarm-Modelling] True
Concurrency?
I posted the following message in
the Swarm list:
-------------------------------------------------------------------------------------------------
Hi,
Is Swarm concurrent (agents run
concurrently) or implements threaded
schedules like "swarm-alike"
Repast?
A bit more detailed. Repast runs the agent action within a
schedule. At
some tick, the agent list is scanned and each agent is given
attention.
But, as far as I know, the agents do not run concurrently.
Within each
tick, the agents are chosen randomly to determine who will
have
attention. Repast implements "simulated concurrency".
Since
Repast claims to be based in Swarm, I wonder what is the
Swarm
behaviour?
Thanks for your help,
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
As a quick note, Repast supports both simulated and
true concurrency.
Repast's simulated concurrency works the way you outlined
below. True
concurrency (i.e., parallel execution) can be achieved
using the Repast
scheduler methods with "duration" parameters.
Setting non-zero
durations will cause the scheduler to concurrently execute
tasks that
have overlapping time durations. If you have multiple CPUs
available
then the tasks will execute in true parallel form on multiple
CPUs. The
Repast scheduler uses thread pooling to make this
efficient. Of course,
model developers are responsible for making
sure that true parallel
execution makes sense for their model. This
generally means that the
model needs to be thread
safe.
Mike
-----------------------------------------------------------------------------------------------------------------
I was aware that Repast scheduler
uses thread pooling. But my understanding of this mechanism (Please! Correct
me.) was that it allows threaded schedules but does not allow threaded
agent tasks. Two or more agents are not "alive" at the same
tick.
As I am working on a paper on
concurrency in Multiagent Frameworks (Repast, Swarm and Ascape), please
correct my understanding of the mechanism.
Any pointer to articles that
would help in the article are fully
appreciated.
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