Question

A set of jobs to be processed on a single machine. What will be the ratio of average job flow time using SPT and EDD rule?

Jobs	Processing time	Due date
A	7	9
B	9	17
C	13	10
D	6	13
E	11	26

• A. 1.116
• B. 1.00
• C. 0.6133
• D. 0.895

Answer 1

The correct option is D 0.895

$\text{Using SPT rule}$

Jobs	Processing time	Job flow time
D	6	6
A	7	13
B	9	22
E	11	33
C	13	46

$\text{Average job flow time}$

$=\frac{46+33+22+13+6}{5}=\frac{120}{5}=24$

$\text{Using EDD rule}$

Jobs	Processing time	Job flow time
D	7	7
A	13	20
B	6	26
E	9	35
C	11	46

$\text{Average job flow time}$

$=\frac{7+20+26+35+46}{5}=\frac{120}{5}=26.8$

$\frac{\text{Average job flow time using SPT rule}}{\text{Average job flow time using EDD rule}}=\frac{24}{26.8}=0.895$