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

running multiple parallel cases in openfoam slows the simulation

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

Like Tree2Likes
  • 2 Post By wyldckat

Reply
 
LinkBack Thread Tools Display Modes
Old   August 20, 2015, 22:00
Default running multiple parallel cases in openfoam slows the simulation
  #1
Senior Member
 
Join Date: Jan 2013
Posts: 118
Rep Power: 5
kkpal is on a distinguished road
Dear all,
I tried to 2 cases in openfoam at the same time, both of them in parallel with 2 processors. I've found that the simulation speed is severely slowed down, compared to running just one case at a time. These two cases surely did not reach the capacity limit of this computer since the computer has 24 processors and 126Gb ram. I suspected that this problem may have dealings with something inside the MPI.
In view of the above finding, I will either have to run my simulation cases, which is quite a lot , with one processors at the same time, or just run one simulation in parallel and then proceed to another. Both of these two choices are not efficient.
Could someone confirm this? And is there a way to resolve this problem and use openfoam more efficiently?
kkpal is offline   Reply With Quote

Old   August 21, 2015, 05:19
Default
  #2
Senior Member
 
Join Date: Mar 2010
Location: Germany
Posts: 147
Rep Power: 8
cutter is on a distinguished road
Hi,

this is not unusual. I don't know your mesh size etc. but the performace is probably limited by memory bandwidth and caches sizes. The fields of
large meshes cannot be kept in cache (even at your really nice machine), they need to be fetched from main memory repeatedly. This problem gets even worse when the cache and bus is used by multiple simulations at the same time.

Cutter
cutter is offline   Reply With Quote

Old   August 21, 2015, 11:08
Default
  #3
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,743
Blog Entries: 39
Rep Power: 103
wyldckat is a glorious beacon of lightwyldckat is a glorious beacon of lightwyldckat is a glorious beacon of lightwyldckat is a glorious beacon of lightwyldckat is a glorious beacon of light
Quick answer: From my blog post Notes about running OpenFOAM in parallel - I have a note about this topic... this post details how to handle those situations: mpirun, best parameters - post #9
kkpal and Bashar like this.
wyldckat 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
Suggestion for a new sub-forum at OpenFOAM's Forum wyldckat Site Help, Feedback & Discussions 20 October 28, 2014 10:04
Can not run OpenFOAM in parallel in clusters, help! ripperjack OpenFOAM Running, Solving & CFD 5 May 6, 2014 15:25
OpenFOAM parallel running error in cluster vishal_s OpenFOAM Running, Solving & CFD 5 March 11, 2014 16:11
Running Error using Compressible OpenFoam Parallel mode dhendria OpenFOAM Running, Solving & CFD 0 February 13, 2014 21:53
Something weird encountered when running OpenFOAM in parallel on multiple nodes xpqiu OpenFOAM Running, Solving & CFD 2 May 2, 2013 04:59


All times are GMT -4. The time now is 22:05.