CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

ANSYS Fluent number of cores

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 30, 2017, 10:36
Lightbulb ANSYS Fluent number of cores
  #1
New Member
 
Jiffy
Join Date: May 2016
Posts: 5
Rep Power: 9
Jiffy is on a distinguished road
Hello,

I have new PC with 2x Intel Xeon CPU E5-2680 v2 (2,8 GHz) and 64 GB RAM. When I setup all cores for computing (40 cores), the PC computed only with 32 (as I could see it in Task manager). When I tried to use only 32 cores, surprisingly it was faster then with 40 cores.

Does anybody know where is the problem? Is there any limitation in number of cores? Or any special setup?

Thank you in advance!!!
Jiffy is offline   Reply With Quote

Old   December 1, 2017, 15:23
Default
  #2
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,649
Rep Power: 65
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
This is a problem of the job scheduler. Since there is only 2x10 physical cores. The best solution is to not use hyperthreading and only run on 20 physical cores. W/ hyperthreading you are at the mercy of the job scheduler.

What does it mean the cpu is only computing with 32 cores? Do you mean that Fluent correctly launches 40 jobs but you only see 32 cores at 100% utilization and the remaining 8 not doing anything (e.g. stuckat 0%)?

Or is it something terrible where you tell Fluent to use launch 40 but it only launches 32?
LuckyTran is offline   Reply With Quote

Old   December 8, 2017, 11:34
Default
  #3
New Member
 
Jiffy
Join Date: May 2016
Posts: 5
Rep Power: 9
Jiffy is on a distinguished road
Thank you very much for your response!

Yes, I meant that Fluent correctly launches 40 cores but only 32 cores work at 100%. The remaining 8 are doing nothing.

It is not terrible But strange, and I just wonder why the Fluent does not use every cores. And second strange thing is, that when I setup 32 cores for computing (when Fluent launching), the computation is much more quicker then if Fluent launches 40 cores.

I disabled the hyperthreading, so I used only 20 physical cores and the computing time was the shortest of all my simulations! So I think it is the best solution for me - using only the physical cores.

Thank you again for your help
Jiffy is offline   Reply With Quote

Old   December 14, 2019, 15:18
Default
  #4
Member
 
Os
Join Date: Jun 2017
Posts: 80
Rep Power: 8
losiola is on a distinguished road
Quote:
Originally Posted by Jiffy View Post
Thank you very much for your response!

Yes, I meant that Fluent correctly launches 40 cores but only 32 cores work at 100%. The remaining 8 are doing nothing.

It is not terrible But strange, and I just wonder why the Fluent does not use every cores. And second strange thing is, that when I setup 32 cores for computing (when Fluent launching), the computation is much more quicker then if Fluent launches 40 cores.

I disabled the hyperthreading, so I used only 20 physical cores and the computing time was the shortest of all my simulations! So I think it is the best solution for me - using only the physical cores.

Thank you again for your help
Hello Jiffy

i am now struglling now with the same situation just like you !
because i ve noticed that my laptop I7 (4 cores ) does actually run the same simulation in twice the time of my workstation ( with 24 cores & 48threads ) .

At first i thought it's my licence that cant support the cores but i guess now that with your topic i can understand the problem .

Once You said that you deactivated the hyperthreasing Do you mean disable it from the BIOS or you just entred 20 cores instead of 40 ?

Many Thanks
losiola is offline   Reply With Quote

Reply

Tags
cores, fluent

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[General] Extracting ParaView Data into Python Arrays Jeffzda ParaView 30 November 6, 2023 22:00
SigFpe when running ANY application in parallel Pj. OpenFOAM Running, Solving & CFD 3 April 23, 2015 15:53
AMI interDyMFoam for mixer danny123 OpenFOAM Running, Solving & CFD 4 June 19, 2013 05:49
number of iterations to converge solution in Fluent as Ansys Workbench output param nnvoro FLUENT 4 May 2, 2013 02:18
DecomposePar unequal number of shared faces maka OpenFOAM Pre-Processing 6 August 12, 2010 10:01


All times are GMT -4. The time now is 22:37.