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RMULT

An RMULT Command sets the seeds for random number generators.

RMULT A,B,C,D,E,F,G

Operands

A - Seed for random number generator number 1. Optional.

The operand must be Null, or PosInteger.

B - Seed for random number generator number 2. Optional.

The operand must be Null, or PosInteger.

C - Seed for random number generator number 3. Optional. The operand must be Null, or PosInteger.

D - Seed for random number generator number 4. Optional. The operand must be Null, or PosInteger.

E - Seed for random number generator number 5. Optional. The operand must be Null, or PosInteger.

F - Seed for random number generator number 6. Optional. The operand must be Null, or PosInteger.

G - Seed for random number generator number 7. Optional. The operand must be Null, or PosInteger.

Example

RMULT ,,111

In this example, random number generator 3 is initialized with a seed of 111.

Action

The RMULT Command is a Queued Command. When the

Simulation Object receives one, it places it at the end of the simulation’s Command Queue.

The RMULT Command initializes up to 7 random number generators with new seeds. Only random number generators

numbered 7 or below can be controlled by an RMULT

Command. However, since the default seed of a random number generator is its entity number, you can in fact have any number of random number generators, and you can choose the initial seed of each. After the first simulation run the seeds can only be controlled easily with the RMULT Command on generators 1-7.

You can select which random number stream GPSS World uses it to calculate random time increments in ADVANCE and GENERATE Blocks, in Fractional Mode TRANSFER and

TRANSFER PICK Blocks and to resolve the scheduling of time ties. This is set in the "Random" page of the Model Settings

Notebook.

CHOOSE View / Settings / Model

then select the Random page. Then fill in the desired

Random Number Stream Entity number in the corresponding entry boxes. The installation default is to use Random Number

Stream number 1 in each case.

Since GPSS World uses multiplicative congruential random number generators, it is possible to control pairs of random number streams for variance reduction purposes. This is done by matching the seeds of the random number generators. If s is the seed for the first random number generator, then a choice of 2147483647-s for the seed of the second random number generator will generate a stream of random numbers with antithetic properties.

Special Restriction

Random number seeds must be positive integers.

Related SNA

RNEntnum - Random number. RNEntnum returns a random integer 0-999 from the random number generator Entnum.

Related Window

The ANOVA Window can perform Analysis of Variance and calculate confidence intervals.

SHOW

A SHOW Command sends an Expression for evaluation by the Simulation Object, and writes the result in the Status Line.

SHOW X

Operand

X - Expression.

Example

SHOW 2#LOG(Q$Barber)

This Command finds the natural logarithm of the SNA Q$Barber, doubles it, and writes the result in the Status Line of the Model Window.

Action

The SHOW Command is an Immediate Command. It is performed when received by the Simulation Object.

The SHOW Command evaluates an Expression in the context of the simulation, and writes the result in the Status Line of the Model Window. Additional messages are sent to any open Journal Windows.

The rules for evaluating Expressions may be found in Section 3.4. Expressions must be well-formed according to the rules of elementary algebra. You may used any of the arithmetic and logic operators listed in Section 3.4.

If SNAs are used in the Expression field, they are evaluated with respect to the Active Transaction. If there is no Active

Transaction because no simulation has been started, an error message will be written. Names which have not been explicitly assigned values cannot be used in Expressions. To do so you must assign a value by an EQU Command before the

Expression is evaluated.

Examples

SHOW C1

shows the system clock in the Status Line.

SHOW 4#(SQR(2)+SIN(C1))

shows the result of 4 times the sum of the square root of 2 and the sine of the system clock.

SHOW N1^W$Chair

shows the result of raising the number of Transactions to have entered Block 1 to the power of the number of Transactions waiting at the Block named Chair.

Special Restrictions

Some SNAs cannot be evaluated unless there is an Active Transaction.

SHOW displays up to 38 characters or digits.

Related Windows

Any valid Expression can be viewed in an

Expressions or Plot Window.

START

A START Command begins a simulation.

START A,B,C,D

Operands

A - Termination count. Required. The operand must be

PosInteger.

B - Printout operand. NP for "no printout". Default is to print a standard report. Optional. The operand must be NP or Null.

C - Not used. Kept for compatibility with older dialects of

GPSS.

D - Chain printout. 1 to include the CEC and FEC in the standard report. Optional. The operand must be Null, or

PosInteger.

Action

The START Command is a Queued Command. When the

Simulation Object receives one, it places it at the end of the simulation’s Command Queue.

The START Command is used to set up and begin the actual simulation. The simulation does not end until the termination count, which is set by Operand A, reaches zero or becomes negative. TERMINATE Blocks are used to reduce the termination count.

The simulation may stop short if a HALT Command is issued, or if a Stop Condition is detected.

Operands B and D are used to control automatic report generation. If Operand B is not used, an standard report is written. If Operand B is NP, which stands for "no printout", no standard report is written. If Operand D is nonzero, the Current

Events Chain (CEC) and the Future Events Chain (FEC) are reported. Otherwise they are not reported. A further discussion of the control and contents of the standard report may be found in Chapters 11 and 12.

Operand C is kept for compatibility with older versions of GPSS. It was used as a "snap" count to put out a report periodically. This Function is available by using more than one START and REPORT Command.

When a START Command is performed:

The Termination Count is set.

Any generate Blocks marked "not started" are primed with a single Transaction.

Random number generators are not reset.

If time is 0, a RESET of the statistics accumulators is performed. See the discussion of the RESET Command in this chapter.

Example

START 1000,,,1

In this example, the Termination Count is set to 1000 and the

simulation is started. When the Termination Count reaches zero or becomes negative (by reduction due to TERMINATE

Blocks in the simulation), a standard report is written which includes information on the Current Events Chain (CEC) and the Future Events Chain (FEC).

Related SNA

TG1 - Termination count.

Related Blocks

TERMINATE - destroy Transaction and optionally reduce the termination count.

STEP

A STEP Command causes the simulation to proceed a specified number of Block entries.

STEP A

Operand

A - Block entry count. Required. A must be a positive integer, more formally, PosInteger.

Example

STEP 1

This Command causes the simulation to proceed exactly one

Block entry and then to stop. The simulation is then said to be in the "Halted" state.

Action

The STEP Command is a Queued Command. When the

Simulation Object receives one, it places it at the end of the simulation’s Command Queue.

The STEP Command causes the Simulation Object to simulate the specified number of Block entries. When a simulation reaches the required number of Block entries, the Simulation

Object sends a message to the Status Line, and any Journal

Windows that are open. The message gives the time, the

Active Transaction number, the current Block of the Active

Transaction, and the next scheduled Block of the Active

Transaction.

A simulation started by a STEP Command does not end when the termination count goes to zero, it ends when the required number of Block entries have occurred.

When a STEP Command is performed:

The termination count is not set.

Any generate Blocks marked "not started" are primed.

Random number generators are not reset.

Hot Key

A STEP 1 Command can be sent to the simulation by pressing

the b + a + 1 key combination. A GPSS World window must have the input focus.

Related Windows

The stepping of simulations can be viewed dynamically in the Blocks Window.

STOP

A STOP Command sets or removes a Stop Condition.

STOP A,B,C

Operands

A - Transaction number. A must be a positive integer. If the A

Operand is omitted, any Transaction number will satisfy the condition. Optional. The operand must be Null, or PosInteger.

B - Block number. If the B Operand is omitted, any Block will satisfy the condition. Optional. The operand must be Null,

Name, or PosInteger.

C - ON or OFF. If the C Operand is omitted, ON is assumed.

Optional. The operand must be ON, OFF or Null.

Example

STOP 100,52

This Command inserts a Stop Condition which will cause a running simulation to stop when Transaction number 100 attempts to enter Block number 52.

Action

The STOP Command is a Queued Command. When the Simulation Object receives one, it places it at the end of the simulation’s Command Queue.

The STOP Command with the ON option inserts a Stop

Condition into the simulation but does not cause the simulation to start. A subsequent START, STEP, or CONTINUE must be entered.

When a simulation reaches a Stop Condition, the Simulation

Object sends a message to the Status Line, and any Journal Windows that are open. The message gives the time, the Active Transaction number, the current Block of the Active

Transaction, and the next scheduled Block of the Active

Transaction.

When a Stop Condition is detected, established Stop Conditions remain in force. If a CONTINUE Command is issued, the CONTINUE Command skips the original Stop Condition but does not remove it. If the same condition occurs again, the simulation will stop again. Stop Conditions must be removed explicitly by entering a new STOP Command

containing the OFF option. They are also removed when a model is Translated.

STOP Commands can be sent by using mousing operations in the Blocks Window. This is discussed in more detail in Chapter

5.

If you skip the A Operand, any Transaction will satisfy the Stop Condition. If you skip the B Operand, any Block will satisfy the

Stop Condition. A STOP Command with no operands will cause the simulation to stop immediately.

Any number of Stop Conditions may be established.

The STOP Command with the OFF option removes any existing Stop Conditions that satisfy the Transaction and Block conditions specified by operands A and B.

Examples

STOP

With no operands, the STOP Command will cause any subsequent simulation to stop immediately.

STOP ,,OFF

This Command removes all Stop Conditions from the simulation.

STOP 2

This Command will cause the simulation to stop when

Transaction 2 becomes the Active Transaction.

STOP ,Chair

This Command will cause the simulation to stop when any

Transaction attempts to enter the Block at location CHAIR.

STOP ,Chair,OFF

This Command will remove all Stop Conditions that specify

Chair as the Block name.

Related Windows

Mouse operations can be used in the Blocks

Window to place and remove Stop Conditions.

STORAGE

A STORAGE Command defines a Storage Entity.

NAME STORAGE A Label / Operand

NAME - Entity Label for this entity. Required. The field must be

Name.

A - Total storage capacity. Required. The operand must be

PosInteger.

Example

MotorPool STORAGE 20

This Command defines a Storage Entity named MotorPool with a total capacity of 20 units.

Action

The STORAGE Command is a Queued Command. When the Simulation Object receives one, it places it at the end of the simulation’s Command Queue.

A STORAGE Command defines a Storage Entity in the simulation. When a Transaction attempts to enter an ENTER

Block, its storage demand is compared with the available storage at the Storage Entity. If the demand can be granted, the Transaction is allowed to enter the ENTER Block and the available storage capacity of the Storage Entity is reduced. If the Transaction’s demand cannot be satisfied, the Transaction comes to rest in the simulation on the Delay Chain of the

Storage Entity. Storage Entities are explained in more detail in

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