when increase compute process solution time does not change

hguvenc · January 7, 2022, 11:35

Hello everyone,

I want to ask that; I have 10 core 20 thread cpu, I started star ccm in paralell on local host and entering 10 process to 18 process. cpu usage changes %50 to %100 but iteration time goes 8.3sec to 8.0sec nearly. There is really a little bit difference. What am I doing wrong? Anyone has answer for that.

when I started 2 simulation same time iteration time changes 15sec.

thanks,

LuckyTran · January 7, 2022, 11:46

Because multi-threading doesn't actually do anything. Even intel has given up it.

After 10, all your new threads are being run on virtual cores. You should be happy seeing any benefit at all.

hguvenc · January 7, 2022, 11:54

Quote:

Originally Posted by LuckyTran

Because multi-threading doesn't actually do anything. Even intel has given up it.

After 10, all your new threads are being run on virtual cores. You should be happy seeing any benefit at all.

Its too annoying to see that cpu working 50% and 100% but solves in the same time.

LuckyTran · January 7, 2022, 11:57

Just turn off multi-threading

hguvenc · January 7, 2022, 11:58

Do you know has mpi selection effects solution time and which one is better?

LuckyTran · January 7, 2022, 12:04

They do but there is no general answer to that. You have to do detailed benchmarks. And it is probably one of the last things you should worry about on a single node machine.

hguvenc · January 7, 2022, 12:06

I look at the internet and user guide to turning off multi-threading. Can you give a little bit info about that?

Sorry if I askıng a lot

LuckyTran · January 7, 2022, 13:09

It is a BIOS setting. Restart your computer (turn it off and on). And then you have to press a certain button within the first few seconds when it turns on before your OS loads. It could be any of the F# keys or del. F10 and F12 are very popular. If you see the Windows logo then you are too late.

Without knowing exactly what motherboard you have, I can't tell you what key you have to press or what the BIOS menu even looks like. It varies widely from one OEM to the next and varies even within an OEM.

hguvenc · January 8, 2022, 02:38

Thank you for your help

January 7, 2022, 11:35	when increase compute process solution time does not change	#1
hguvenc New Member Halit Guvenc Join Date: Nov 2021 Location: Turkey Posts: 14 Rep Power: 4	Hello everyone, I want to ask that; I have 10 core 20 thread cpu, I started star ccm in paralell on local host and entering 10 process to 18 process. cpu usage changes %50 to %100 but iteration time goes 8.3sec to 8.0sec nearly. There is really a little bit difference. What am I doing wrong? Anyone has answer for that. when I started 2 simulation same time iteration time changes 15sec. thanks,

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January 7, 2022, 11:46		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Because multi-threading doesn't actually do anything. Even intel has given up it. After 10, all your new threads are being run on virtual cores. You should be happy seeing any benefit at all.

January 7, 2022, 11:57		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Just turn off multi-threading

January 7, 2022, 11:58		#5
hguvenc New Member Halit Guvenc Join Date: Nov 2021 Location: Turkey Posts: 14 Rep Power: 4	Do you know has mpi selection effects solution time and which one is better?

January 7, 2022, 12:04		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	They do but there is no general answer to that. You have to do detailed benchmarks. And it is probably one of the last things you should worry about on a single node machine.

January 7, 2022, 12:06		#7
hguvenc New Member Halit Guvenc Join Date: Nov 2021 Location: Turkey Posts: 14 Rep Power: 4	I look at the internet and user guide to turning off multi-threading. Can you give a little bit info about that? Sorry if I askıng a lot

January 7, 2022, 13:09		#8
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	It is a BIOS setting. Restart your computer (turn it off and on). And then you have to press a certain button within the first few seconds when it turns on before your OS loads. It could be any of the F# keys or del. F10 and F12 are very popular. If you see the Windows logo then you are too late. Without knowing exactly what motherboard you have, I can't tell you what key you have to press or what the BIOS menu even looks like. It varies widely from one OEM to the next and varies even within an OEM.

January 8, 2022, 02:38		#9
hguvenc New Member Halit Guvenc Join Date: Nov 2021 Location: Turkey Posts: 14 Rep Power: 4	Thank you for your help