CSIM19 tutorial

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CSIM19 tutorial

• Reference http//www.mesquite.com/

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Introduction

• CSIM19
• A library of routines
• Process-oriented, discrete-event simulation
  package for use with C or C programs
• A CSIM program
• It models a system as a collection of CSIM
  processes which interact with each other

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Introduction

• CSIM provides the following simulation objects
• CSIM processes processes
• CSIM objects facilities, storages, buffers,
  events, mailboxes
• Statistics tables, qtables, meters,

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Simulation time

• CSIM maintains a simulation clock, with value
  equals to current time in the model
• Different from the CPU time used or the real
  world time
• Starts at zero
• A double precision floating point

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Simulation time

• Retrieving the current time
• 1. Simtime function
• Prototype double simtime (void)
• Example x simtime ()
• 2. Reference the variable clock
• Example x clock
• Delaying for an amount of time
• Prototype void hold (double amount_of_time)
• Example hold (1.0)

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Process

• It is the active entities in a model
• It is a procedure which executes the create
  statement
• A process must be in four states
• Active computing
• Ready to begin computing
• Holding
• Waiting for an event

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Initiating a process

• Prototype void proc (arg1, , argn)
• Example my_proc (a, 64, proc)
• Note
• A create statement must appear in the initiated
  process
• A process cannot return a function value

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Creating a process

• Prototype void create (char name)
• Example create (customer)
• Note
• Executes at the beginning of a process
• Process can initiate other processes
• No simulation time passes

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Process operation

• Processes appear to operate simultaneously at the
  point in simulation time
• Processes execute until they suspend themselves
  by
• Execute a hold statement
• The process is put into a queue
• Execute a csim_terminate statement

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Terminating a process

• A process terminates when
• A normal procedure exit, or
• Executes a terminate statement
• Prototype void csim_terminate (void)
• Example csim_terminate ()

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Changing the process priority

• Initial priority of a process is inherited from
  the initiator of that process
• Default priority is 1
• Prototype void set_priority (long new_priority)
• Example set_priority (5)
• Note
• Must appear after the create statement
• Lower values represent lower priorities

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Reporting process status

• Print the status of each active process
• Prototype void status_processes (void)
• Example status_processes ()

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Facilities

• It models a resource in a simulated system
• Processes are ordered in a facility queue by
  their priorities.
• A higher priority process is ahead of a lower
  priority process.

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Declaring and initiating a facility

• Declaring
• Dynamic example facility fd
• Initiating
• Prototype facilityfacility (char name)
• Dynamic example fd new facility (fac)
• Static example facility fs (fac)
• Note
• The facility name is only used only to identify
  the facility in output reports and trace messages

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Using a facility

• A process can use a facility for a specified
  interval of time.
• If the facility is free, then the process gains
  exclusive use of the server until the end of the
  usage interval
• If the facility is busy, then the process is put
  in a queue of waiting processes.
• Prototype void facilityuse (double
  service_time)
• Example fd-gtuse(1.0)

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Reserving and releasing a facility

• In case a process acquires a server other than
  entering the usage interval
• Reserve to gain exclusive use of a server
• Release to relinquish use of the server
• Prototype void facilityreserve (void)
• void facilityrelease (void)
• Dynamic example
• fd-gtreserve () fd-gtrelease ()

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Reserving and releasing a facility

• Note
• When a process executes a reserve, it either
• 1) gets use of the server, or
• 2) it is suspended and placed in a waiting queue
• The process releasing a server must be the same
  process reserved it. Otherwise, use
  release_server ()
• fd-gtreserve (f) hold (t) fd-gtrelease (f)
• fd-gtuse (t)
• fd-gtreserve (f) hold (exponential(t))
  fd-gtrelease (f)
• ! fd-gtuse (exponential(t))

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Producing reports

• Prototype void facility_report (void)
• Example facility_report ()

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Releasing a specific server at a facility

• Used when one process reserves a facility and
  then for another process to release
• Prototype void facilityrelease_server (long
  server_index)
• Dynamic example server_index fd-gtreserve ()
• fd-gtrelease_server (server_index)
• Note
• The first process has to save the index of the
  server and gives it to the second process
• This is the same as release except the ownership
  is not checked

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Declaring and initializing a multi-server facility

• Prototype facility_msfacility_ms (char name,
  long number_of_servers)
• Dynamic example cpud new facility_ms (cpus,
  2)
• Static example facility_ms cpus (cpus, 2)
• Note
• A process gains access to any free server when
  reserve()

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Facility sets

• Prototype facility_setfacility_set (char
  name, long num_of_facilities)
• Dynamic example facility_set diskd diskd new
  facility_set (disk, 10)
• Static example
• facility_set disks (disk, 10)
• disksi.use (exponential(1.0))

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Events

• Used to synchronize the operations of CSIM
  processes
• An event can only be in occurred or not occurred
  state

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Declaring and initializing an event

• Prototype eventevent (char name)
• Dynamic example event ed ed new event
  (done)
• Static example event es (done)

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Waiting for an event

• Waiting for an event
• Prototype void eventwait (void)
• Dynamic example e-gtwait ()
• Waiting with a time-out
• Prototype long eventtimed_wait (double tout)
• Dynamic example res ed-gttimed_wait (100.0) if
  (res ! TIMED_OUT)

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Queuing for an event

• Prototype void eventqueue (void)
• Dynamic example ed-gtqueue ()
• Note
• This behaves like wait function, except that at
  each time event is set only one queued process is
  resumed.

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Setting an event

• Prototype void eventset (void)
• Dynamic example ed-gtset ()
• Note
• It causes all waiting processes and one queue
  process to be resumed
• If there is no waiting event, the event will be
  in occurred state upon return from set function

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Clearing an event

• Prototype void eventclear (void)
• Dynamic example ed-gtclear ()
• Note
• Clearing an event that is in not occurred state
  has no effect

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Event sets

• Prototype event_setevent_set (char name, long
  number_of_events)
• Dynamic example event_set ed_set
• ed_set new event_set (events, 10)
• Static example
• event_set es_set (events, 10)
• es_set3.set ()

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Producing Report

• Status report
• Prototype void status_events (void)
• Dynamic example status_events ()

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Tables

• To gather statistics on a sequence of discrete
  values such as interarrival times, service times,
  
• It does not actually store the recorded values,
  it just simply updates the statistics
• The statistics maintained include min, max,
  range, mean, var, std dev, coef of var
• Can add histogram, calculation of confidence
  intervals

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Declaring and initializing a table

• Prototype tabletable (char name)
• Dynamic example table td
• td new table (response time)
• Static example table ts (response time)

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Tabulating values

• Prototype void tablerecord (double value)
• Dynamic example td-gtrecord (1.0)
• Note
• Tables are designed to maintain statistics on
  data type of type double only

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Producing reports

• Prototype void tablereport (void)
• Dynamic example td-gtreport ()
• Note
• report_tables () to produce reports for all
  tables

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Histograms and confidence intervals

• Histograms
• Prototype void tableadd_histogram (long
  nbucket, double min, double max)
• Static example ts.add_histogram (10, 0.0, 10.0)
• Confidence intervals
• Prototype void tableconfidence (void)
• Static example ts.confidence ()