Simulation Algorithms for Atomic DEVS
Encyclopedia
Given an atomic DEVS model, simulation algorithms are methods to generate the model's legal behaviors which are trajectories not to reach to illegal states. (see Behavior of DEVS
). [Zeigler84] originally introduced the algorithms that handle time variables related to lifespan
and elapsed time 
by introducing two other time variables, last event time, 
, and next event time 
with the following relations:
and
where
denotes the current time. And the remaining time,
.
Since the behavior of a given atomic DEVS model can be defined in two different views depending on the total state and the external transition function (refer to Behavior of DEVS
), the simulation algorithms are also introduced in two different views as below.
DEVS-simulator
variables:
parent // parent coordinator
// time of last event
// time of next event
// the associated Atomic DEVS model
when receive init-message(Time
)
when receive star-message(Time
)
if
then
error: bad synchronization;
send y-message(
) to parent;
, the last event time,
is set by the current time,
, thus the elapsed time
becomes zero because 
.
when receive x-message(
, Time 
)
if
and 
false then
View 2: total states = states * lifespans * elapsed times
Notice that as addressed in Behavior of Atomic DEVS, depending on the value of
return by 
, last event time,
, and next event time,
,consequently, elapsed time, 
, and lifespan
, are updated (if 
) or preserved (if 
).
when receive x-message(
, Time 
)
if
and 
false then
error: bad synchronization;
if
then
Behavior of DEVS
Behaviors of a given DEVS model is a set of sequences of timed events including null events, called event segments which make the model move one state to another within a set of legal states...
). [Zeigler84] originally introduced the algorithms that handle time variables related to lifespan
and elapsed time by introducing two other time variables, last event time, , and next event time with the following relations:and
where
denotes the current time. And the remaining time,.Since the behavior of a given atomic DEVS model can be defined in two different views depending on the total state and the external transition function (refer to Behavior of DEVS
Behavior of DEVS
Behaviors of a given DEVS model is a set of sequences of timed events including null events, called event segments which make the model move one state to another within a set of legal states...
), the simulation algorithms are also introduced in two different views as below.
Common parts
Regardless of two different views of total states, algorithms for initialization and internal transition cases are commonly defined as below.DEVS-simulator
variables:
parent // parent coordinator
// time of last event // time of next event// the associated Atomic DEVS modelwhen receive init-message(Time
)when receive star-message(Time
)if
thenerror: bad synchronization;
send y-message(
) to parent;View 1: total states = states * elapsed times
As addressed in Behavior of Atomic DEVS, when DEVS receives an input event, right calling, the last event time, is set by the current time, , thus the elapsed time becomes zero because .when receive x-message(
, Time )if
and false then
error: bad synchronization;
View 2: total states = states * lifespans * elapsed times Notice that as addressed in Behavior of Atomic DEVS, depending on the value of
return by , last event time,, and next event time,,consequently, elapsed time, , and lifespan, are updated (if ) or preserved (if ).when receive x-message(
, Time )if
and false thenerror: bad synchronization;
if
thenSee also
- Atomic DEVS
- Behavior of atomic DEVS
- Simulation algorithms for coupled DEVSSimulation Algorithms for Coupled DEVSGiven a coupled DEVS model, simulation algorithms are methods to generate the model's legal behaviors, which are a set of trajectories not to reach illegal states...