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4
Working with Signals
Multivalued Signals
In this section...
“Zero-Duration Values of Signals” on page 4-18
“Importance of Zero-Duration Values” on page 4-18
“Detect Zero-Duration Values” on page 4-19
Zero-Duration Values of Signals
Some output signals from SimEvents blocks produce a new output value for each
departure from the block. When multiple departures occur in a single time instant, the
result is a multivalued signal. That is, at a given instant in time, the signal assumes
multiple values in sequence. The sequence of values corresponds to the sequence of
departures. Although the departures and values have a well-defined sequence, no time
elapses between adjacent events.
Scenario: Server Departure and New Arrival
For example, consider the scenario in which an entity departs from a single server at
time T and, consequently, permits another entity to arrive from a queue that precedes
the server. The statistic representing the number of entities in the server is 1 just before
time T because the first entity has not completed its service. The statistic is 1 just after
time T because the second entity has begun its service. At time T, the statistic is 0 before
it becomes 1 again. The value of 0 corresponds to the server's empty state after the first
entity has departed and before the second entity has arrived. Like this empty state, the
value of 0 does not persist for a positive duration.
Scenario: Queue Length
Another example of zero-duration values is in “Plot the Queue-Length Signal”, which
discusses a signal that indicates the length of a queue. At time 3, the queue length
increases by 1 because a new entity arrives. Subsequently but still at time 3, the queue
length decreases by 1 because an entity advances from the queue to the server. That is,
the larger value at time 3 does not persist for a positive duration.
Importance of Zero-Duration Values
The values of signals, even values that do not persist for a positive duration, can help
you understand or debug your simulations. In the example described in “Scenario: Server
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