Event-Driven Models
GoldSim 2006 User Conference
Slide 1
Vancouver, B.C.
Continuous-time vs
Discrete-event Models
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GoldSim was originally built as a continuous-time
simulator: “Rates of change”, predefined time steps...
Gradually more and more discrete-event modeling
capabilities have been added:
– Timed Event Generator
– Discrete Changes
– Reservoir overflows
– Reliability Failures & Repairs
– Etc. etc.
These changes have led to a much more complex
model-updating logic.
GoldSim 2006 User Conference
Slide 2
Vancouver, B.C.
Events and Discrete Changes
 An “Event” is a special type of output that is
sent out at discrete times during a
simulation. It carries no information other
than its occurrence.
 A “Discrete Change” is like an Event, but it
also carries a value and an instruction:
“Add” or “Replace”.
 Events can only connect to a “Trigger” in
another element.
 It’s not their primary purpose, but Discrete
Changes can also be used in Triggers.
GoldSim 2006 User Conference
Slide 3
Vancouver, B.C.
Elements that can Interrupt the Clock
 The following element types can insert
scheduled events that interrupt the model
clock:
– Timed Event Generator
– Reservoir overflow, underflow
– Reliability failure time, repair time
– Time Series element (discrete changes)
– Event Delay
– Discrete Change Delay
– Fund (interest charges)
– Option (on maturity)
GoldSim 2006 User Conference
Slide 4
Vancouver, B.C.
The Timed Event Generator
 Comes in five
flavors
 Has Cum_Emitted
output
GoldSim 2006 User Conference
Slide 5
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Interrupting the Clock
 The user can disable
clock interruption if
desired:
GoldSim 2006 User Conference
Slide 6
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The Trigger Dialog
 Comes with five flavors
of trigger input.
 Optionally, after the
triggering event, the
trigger will wait until a
specified condition is
true.
 Optionally, it will then
“fire” only if another
condition is true.
GoldSim 2006 User Conference
Slide 7
Vancouver, B.C.
Event-processing Elements
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Emit only:
– Timed Event Generator
– Reservoir overflow, underflow
Receive only:
– Conditional Container
– Stochastic
Emit & Receive:
– Event Delay
– Triggered Event Generator
– Decision
– Random Choice
– Milestone
– Status
– Discrete Change
– Reliability
– Splitter, Allocator
– Option
GoldSim 2006 User Conference
Slide 8
Vancouver, B.C.
GoldSim’s Updating Process
 When a model is being edited, GoldSim
maintains a ‘causality sequence’ that is used
at run time.
 Links between elements are not made unless
a valid causality sequence can be
established.
 Separate, private causality sequences exist
for Submodels and for Containers with the
‘Treat as Subsystem’ option selected.
GoldSim 2006 User Conference
Slide 9
Vancouver, B.C.
Discrete-Change-processing Elements
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Discrete Change Generator
Time Series element (discrete changes)
Reservoir
Discrete Change Delay
Splitter, Allocator
Fund (interest charges)
Option (on maturity)
Insurance
GoldSim 2006 User Conference
Slide 10
Vancouver, B.C.
GoldSim’s Updating Process (simplified)
1. Update static elements in sequence. Supported
element types:
 Data
 Expression
 Stochastic
 Selector
 Table
2. Update all initial values (inputs must be static).
3. For each time step:
1. Set the clock to the new time.
2. Process any ‘dynamic’ elements that can change
with time.
3. Update all function elements in sequence.
GoldSim 2006 User Conference
Slide 11
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F10: the Causality Sequence
3.14
16
Mean
GoldSim 2006 User Conference
Slide 12
dt
Random
Integrator1
Vancouver, B.C.
X
X
Expression1
Dynamic Elements
 These elements have outputs that represent
‘State variables’ for the model.
 Those outputs are available by any element
at any time.
 This allows such element to reference their
own current values, directly or indirectly.
 Some of those outputs can be hybrids
(“Front/Back”), which can change with time
and also during the function update.
– Elements that reference front/back outputs
TRY to sequence after the output, but they
don’t have to.
GoldSim 2006 User Conference
Slide 13
Vancouver, B.C.
Phew!
GoldSim 2006 User Conference
Slide 14
Vancouver, B.C.