Gpss programming (general purpose system simulation) ebubekir siddik nergiz

GPSS PROGRAMMING (GENERAL PURPOSE SYSTEM SIMULATION)

• EBUBEKIR SIDDIK NERGIZ

Simulation with GPSS

• GPSS is a programme had been improved for system simulation.

• GPSS is a way to solve the Monte Carlo type of simulation problems.

• Gpss uses random numbers and it has commands such as ENTER, LEAVE, QUEUE and DEPART that are available for system simulation.

THE COMMANDS ON GPSS

• GENERATE

• It is a command that used for arriving to a transaction.

• We need a time period that decided by the computer

• As an illustration transactions can be interarrival times.

• The programme use uniform distribution if it is not mentioned

• If the arrival times are given with a function we use GENERATE FN$ COMMAND

• ARRIV FUNCTION RN1, D6 ARRIVAL CUMULATIVE DISTRIBUTION 0.19,0/0.50,1/0.77,2/0.88,3/0.96,4/1.0,5

• GENERATE FN$ ARRIV

• If a function is not used such as “GENERATE 5,2” then the programme is gonna use uniform distribution with mean =5

THE COMMANDS ON GPSS

• ADVANCE

• This command is used to show the time expended during the service.

• It has the same using prodecedure with Generate command.

• If the service time is given with a function we use

• ADVANCE FN$SERVE

• Else we use the command without a function such as ADVANCE 5,4

• Then we mean that the mean of the distribution is 5 and the values from 1 to 9 are chosen with the same chance.

• TERMINATE

• we use the command at the end of the all models constituted.

THE COMMANDS ON GPSS

• ENTER-LEAVE AND SEIZE-RELEASE

• These commands are uses together and tell about two function. Firstly they control the entrance and exit from the advance command. If we use Enter-Leave commands ; then the system does not allow to Advance command to have more parts from the storage command lets.

• If we use Seize and release then Advance has only one part.

• The second function is that the commands have capacity and some statistic about the operations.

THE COMMANDS ON GPSS

• QUEUE AND DEPART

• These commands constitutes statistics about the queues.

• MODEL SEGMENT 1

• GENERATE FN$ARRIV

• QUEUE LINE

• ENTER XEROX

• DEPART LINE

• ADVANCE FN$

• LEAVE XEROX

• TERMINATE

• START :this commands give start to the simulation.

THE COMMANDS ON GPSS

• SIMULATE : The command is at the beginning of the of the simulation. It must be at least at the eighth line, else the programme fails.

• END : The command says that the operation has finished then new operations could be get start.

• STORAGE: This command says that the system has one more segments.

THE COMMANDS ON GPSS

• START: Give start to working the model constituted.

• CLEAR:Deletes all the statistic.

• JOB: by the command job we can hold two different Gpss algorithms, job command deletes the results of the first transaction then set the system agin for the new simulation and sets generating new random numbers.

• RESET: reset command makes zero the reletive clock and sets again the resulted statistics but does not set generating new numbers.

FUNCTIONS AT GPSS

• A function starts from second line.

• The maximum number of the letters that the name of the function has is 5.

• The last two characters could be number or letter but the first three characters must be letter.

• RN1,RN2,RN3,RN4,RN5,RN6,RN7,RN8 ; the programme use these commands for generating random numbers.

• Dn is the second operand and means the distribution is discrete and has n categories.

• 0.19,0/0.50,1/0.77,2/0.88,3/0.96,4/1.0,5

THE STATISTIC OF THE QUEUES

• TOTAL ENTRIES: The total number of the entities at the system.

• ZERO ENTRIES: The number of the entities that had their service without being at the queue.

• AVERAGE TIME/TRANSACTION: The average time of the all entities at the system.

THE STATISTIC OF THE SERVICE

• STORAGE: Shows the name of the transaction.

• CAPACITY: The number of the transactions that had the service at the system.

• AVERAGE CONTENTS: The avarage transaction used the service. If the system works with the maximum capacity then the value of the capacity and the value of the avarage contents are gonna be same.

• ENTRIES: The number of the entities that gonna get the service.

• AVERAGE TIME/UNIT: The avarage time for the number of the entities get the service.

• PERCENT AVAILABILITY: The percent of the productivity at the system.

• CURRENT CONTENTS: available transaction number at any time when the simulation finished.

AIRPORT SIMULATION ONE RUNWAY

• SIMULATE

• TIME FUNCTION RN1,D9

• 0.04,0/0.12,1/0.44,2/0.60,3/0.72,4/0.84,5/0.92,6/0.96,7/1.0,8/

• SERVEFUNCTION RN2,D5

• 0.12,2/0.44,3/0.72,4/0.88,5/1.0,6/

• GENERATE FN$TIME..,185

• QUEUE LINE

• SEIZE RUNWAY

• DEPART LINE

• ADVANCE FN$SERV

• RELEASE RUNWAY

• TERMINATE 1

• START 185

• At the first programme advance command includes serve function, but at the second advance command the distribution is discrete uniform distribution with mean = 2,

• Seize and release commands are used for control the entrances and exits to the system constituted.

• After generate command we may use functions or another distributions.

THE RESULTS

THE RESULTS

A example given with the programme

• ; GPSS World Sample File - BARBER.GPS.

• ***********************************************************************

• * *

• * Barber Shop Simulation *

• * *

• ***********************************************************************

• Waittime QTABLE Barber,0,2,15 ;Histogram of Waiting times

• GENERATE 3.34,1.7 ;Create next customer.

• TEST LE Q$Barber,1,Finis ;Wait if line 1 or less

• * else leave shop

• SAVEVALUE Custnum+,1 ;Total customers who stay

• ASSIGN Custnum,X$Custnum ;Assign number to customer

• QUEUE Barber ;Begin queue time.

• SEIZE Barber ;Own or wait for barber.

• DEPART Barber ;End queue time.

• ADVANCE 6.66,1.7 ;Haircut takes a few minutes.

• RELEASE Barber ;Haircut done. Give up the barber.

• Finis TERMINATE 1 ;Customer leaves.

REFERENCES

• 1.GÜNES MUSTAFA, BENZETİM VE GPSS PROGRAMLAMA İZMİR,1996

• 2.HACIMENNİ EMEL,COURSE NOTES

• 3.www.minuteman.com