1
GPSS
(Part III)
Discrete Event Simulation
2005- 2006 Fall Term
Prof. Dr. Nadir Yücel, Asst. Prof. Dr. A. Şima Uyar
Example
Patients arrive at the emergency room of a hospital with arrivals
distributed according to the Poisson distribution. On the average, 30
minutes pass between the patients’ arrivals. There is only one nurse
in the emergency room. The patients are first examined by this nurse,
whose service time is an exponentially distributed random variable
with a mean of 10 minutes. The nurse groups 45% of the patients as
CW (can wait) and the remaining 55% as NIA (need immediate
attention). There are two doctors in the emergency room. The
priority of the patients grouped as NIA are higher. The examination
time of the doctors for the NIA patients is an exponentially
distributed random variable with mean 45 minutes. 75% of these
NIA patients are sent to the lab to get some tests done. The
remaining 25% is treated and sent home. The time it takes for the
test results to be ready is an exponentially distributed random
variable with mean 30 minutes.
Example (
cntd.
)
When the test results are ready, the patients have to be re-
examined by any one of the doctors, however their priority
is now less than that of a patient who was originally labeled
as CW and has not yet seen a doctor. The time it takes for
a doctor to read the test results and treat the patient
accordingly is an exponentially distributed random variable
with mean 15 minutes. After this treatment, the patient is
sent home. The time it takes for a doctor to treat a CW
patient is an exponentially distributed random variable with
mean 30 minutes. After treatment, they are sent home.
Simulate the emergency room for 8 hours (assuming no
breaks) and measure the queues for service at the four
waiting points.
DRS STORAGE 2
*
GENERATE (EXPONENTIAL(1,30,1)),,,,10
QUEUE NURSEQ
SEIZE NURSE
DEPART NURSEQ
ADVANCE (EXPONENTIAL(1,10,1))
RELEASE NURSE
TRANSFER .45,,CW
*
NIA PRIORITY 15
QUEUE NIAQ1
ENTER DRS,1
DEPART NIAQ1
ADVANCE (EXPONENTIAL(1,45,1))
LEAVE DRS,1
TRANSFER 0.25,,HOME
*
PRIORITY 5
ADVANCE (EXPONENTIAL(1,30,1))
QUEUE NIAQ2
ENTER DRS,1
DEPART NIAQ2
ADVANCE (EXPONENTIAL(1,15,1))
LEAVE DRS,1
HOME TERMINATE 0
CW QUEUE CWQ
ENTER DRS,1
DEPART CWQ
ADVANCE (EXPONENTIAL(1,30,1))
LEAVE DRS,1
TERMINATE 0
*
GENERATE 480
TERMINATE 1
Functions
two types of functions:
discrete functions
continuous functions
function definition consists of:
function control statement
function follower statement
Functions
function control statement
label FUNCTION argument,type_count
type: D for discrete, C for continuous
count: number of paired points
function follower statement
paired function points
