CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Why the parallel computation is slow

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

LinkBack Thread Tools Search this Thread Display Modes
Old   May 1, 2008, 03:03
Default Dear friends: I am doing t
Senior Member
ztdep's Avatar
p ding
Join Date: Mar 2009
Posts: 404
Rep Power: 16
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
Dear friends:
I am doing the parallel computation of tutorial 2.3 dam break. my computer is xeon 3.0 with 2 cores. so i decompose the domain with 2 parts.
but i found that the parallel computation is slow that the single core computation.
so would you please tell me what is the reason.
ztdep is offline   Reply With Quote

Old   May 1, 2008, 05:55
Default Hi The dambreak case is ap
Senior Member
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Copenhagen, Denmark
Posts: 1,889
Rep Power: 34
ngj will become famous soon enoughngj will become famous soon enough

The dambreak case is approx 2000 cells, thus 1000 cells per processor. A thread at the forum states that below 100000 cells per processor does not decrease the computational time, as the exchange of information increase faster than the decreased computational time. (rule of thumb).
You are well below the 'limit' of 100000 thus if you increase the number of cells you will reach a point where two processors are faster.

- Niels
Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.
ngj is offline   Reply With Quote


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
Slow down on local parallel Roger CFX 1 October 9, 2008 18:15
Parallel computation Shrinivas Main CFD Forum 4 July 26, 2007 16:00
slow down running in parallel laf FLUENT 1 April 4, 2007 03:48
Parallel computation Jonas Pedro Caumo CFX 6 December 19, 2006 15:51
parallel computation lenson Siemens 6 April 11, 2005 10:14

All times are GMT -4. The time now is 04:20.