[GridSim-users] Question regarding simulation time

[Chainan S. <ch...@sc...>]

Hi,

I was studying the sample code which provided in
http://www.gridbus.org/gridsim/example/index.html Specifically, my
problem was coming from the example 7 (Test.java & TestCase1.java) when
running the simulation. The allocation policy was space sharing.

There are 2 users (User_0 and User_1) I saw all the Gridlet from User_0
start queuing for processing earlier than User_1 but the lenght of
Gridlet (which seems to use as Gridlet size, in_file size, and out_file
size) are all the same. Given the User_1 has 5 times higher bandwidth,
then, I would assume that the User_1 start time should be earlier than
User_0. However, here are the result of simulation

Here are the detail.
All Gridlet schedules onto 1 Machine with 3 PEs.
User_0 (Bandwidth 1000) has
	- Gridlet#0 size 1000 submitted at 11.00 starts at 11.00
	- Gridlet#1 size 2000 submitted at 35.00 starts at 35.00
	- Gridlet#2 size 3000 submitted at 75.00 starts at 120.00
	- Gridlet#3 size 4000 submitted at 131.00 starts at 313.00

User_1 (Bandwidth 5000) has
	- Gridlet#0 size 1000 submitted at 19.00 starts at 19.00
	- Gridlet#1 size 2000 submitted at 51.00 starts at 112.00
	- Gridlet#2 size 3000 submitted at 99.00 starts at 236.00
	- Gridlet#3 size 4000 submitted at 163.00 starts at 421.00

As shown above, I can't understand how it works here. User with higher
bandwidth should be able to finish uploading the file to the processing
machine first and, thus, the job should be ready to submit earlier.
Therefore, I tried to make sure if this is about bandwidth things by
hardcode in the TestCase1.java in createGridlet method by fixing the
size of input file. (i.e. third parameter of Gridlet constructor) As
expected, all Gridlet starts at 3rd second of simulation time. (This is
considered immediate as the code wait 3 units of time in the beginning)
So, I'm quite sure that the delay is coming from the simulation of file
transfer that required before the program execution. So, why the higher
bandwidth is slower? Perhaps, I misunderstood at some points and confuse
myself. Could anyone kindly help me out on this?

Thank you.

Best Regards,
Chainan Satayapiwat
Research Student, Tohoku University