CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

Execution Time after few iterations very high

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 11, 2012, 04:47
Default Execution Time after few iterations very high
  #1
Senior Member
 
Tobi's Avatar
 
Tobias Holzmann
Join Date: Oct 2010
Location: Leoben (Austria)
Posts: 1,077
Blog Entries: 4
Rep Power: 19
Tobi will become famous soon enough
Send a message via ICQ to Tobi Send a message via Skype™ to Tobi
Hi all,

I have a question to you. After starting my simulation (~700.000 cells on 10 cores : ~ 70.000 cells per core) the execution time of the first 6 iterations is round about 4 seconds. After that the execution time goes to very high values.

Is that normal? Depends on the cores (too many?)?
Does anyone has some advices?

Thanks tobi
Attached Images
File Type: jpg ExecutionTime.jpg (54.8 KB, 15 views)
Tobi is offline   Reply With Quote

Old   September 11, 2012, 17:27
Default
  #2
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 8,251
Blog Entries: 34
Rep Power: 84
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Hi Tobi,

Are you certain this is a parallel related problem? Doesn't this behavior occur when running in serial?

From your description, it's very hard to assess the reason why this might be happening. It could be due to:
  • NFS acting up, in case you're using more than one machine.
  • The number of iterations for pressure increases considerably. This could be due to various other reasons, such as mesh, fvSchemes, fvSolution....
  • Can also depend on the solver or type of simulation you're trying to perform: simpleFoam, pimpleFoam, interFoam, interDyMFoam, etc etc...
Best regards,
Bruno
wyldckat is offline   Reply With Quote

Old   September 12, 2012, 03:48
Default
  #3
Senior Member
 
Tobi's Avatar
 
Tobias Holzmann
Join Date: Oct 2010
Location: Leoben (Austria)
Posts: 1,077
Blog Entries: 4
Rep Power: 19
Tobi will become famous soon enough
Send a message via ICQ to Tobi Send a message via Skype™ to Tobi
Quote:
Originally Posted by wyldckat View Post
Hi Tobi,

Are you certain this is a parallel related problem? Doesn't this behavior occur when running in serial?

From your description, it's very hard to assess the reason why this might be happening. It could be due to:
  • NFS acting up, in case you're using more than one machine.
  • The number of iterations for pressure increases considerably. This could be due to various other reasons, such as mesh, fvSchemes, fvSolution....
  • Can also depend on the solver or type of simulation you're trying to perform: simpleFoam, pimpleFoam, interFoam, interDyMFoam, etc etc...
Best regards,
Bruno
Hi Bruno,
thanks for your replay. I have no experience in - how many cores are good for a cfd calculation - that the cores are working good and dont transfer data to each of them.

In that case I think its not a parallel problem

But thanks for your replay. I was just wondering why it is so.
Maybe it is the fact, that I start from a solution and mapped it to the new mesh (extended mesh).

Tobi
Tobi is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3 bookie56 OpenFOAM Installation 8 August 13, 2011 04:03
Extrusion with OpenFoam problem No. Iterations 0 Lord Kelvin OpenFOAM 6 April 12, 2011 11:24
MRFSimpleFOAM goes divergenced! renyun0511 OpenFOAM Running, Solving & CFD 0 November 19, 2009 03:11
Negative value of k causing simulation to stop velan OpenFOAM Running, Solving & CFD 1 October 17, 2008 05:36
Multicomponent fluid Andrea CFX 2 October 11, 2004 05:12


All times are GMT -4. The time now is 08:09.