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

Multi domain performance penalty????

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 13, 2007, 21:59
Default Multi domain performance penalty????
  #1
Stu
Guest
 
Posts: n/a
Can someone tell me if there is a performance penalty when using multiple domains in a sim. Example, I have a large tank, that I have meshed using icem and cfx-mesh. CFX-mesh for the more complex inlet pipes and Icem for the bulk of the rest of the tank. I join the domains together in cfx-pre and all works well.

Neglecting any difference in nodes/elements/tets/hexes, would the solution take longer to solve because it is using 2 doamins, or would it be faster if I did the entire mesh using 1 domain.

Thanks Stu

  Reply With Quote

Old   June 14, 2007, 06:43
Default Re: Multi domain performance penalty????
  #2
Joe
Guest
 
Posts: n/a
In the problems I've solved I've noticed little to no penalty. These were simple linear geometries with a domain interface in the middle.
  Reply With Quote

Old   June 14, 2007, 19:41
Default Re: Multi domain performance penalty????
  #3
Gert-Jan
Guest
 
Posts: n/a
The GGI's will deliver a small penalty.

For parallel processing the penalty can be larger. CFX has the drawback that each partition needs at least a part of each domain. So when you have 10 small parts and 1 large part and 3 processors, these 10 small parts are partitioned over the 3 processors as well as the large parts. Even if the 10 small parts would fit on 1 processor.

Gert-Jan
  Reply With Quote

Old   June 14, 2007, 19:46
Default Re: Multi domain performance penalty????
  #4
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

Whether multiple domains decreases efficiency is problem dependant. The issues are:

Increased efficiency due to: 1) Possibility of improved mesh quality and sizing compared to single domain

Decreased efficiency due to: 1) In parallel, partitioning is done on a domain by domain basis (by default) so there the partition interface area increases. 2) There is an overhead in interfaces. 1 to 1 interfaces have almost no overhead but GGI interfaces have a small overhead.

The balance of these issues determines the effect of the interfaces.

Glenn Horrocks
  Reply With Quote

Old   June 14, 2007, 23:36
Default Re: Multi domain performance penalty????
  #5
johnny
Guest
 
Posts: n/a
By default, CFX runs in "Independent Partitioning" which behaves as Gert-Jan describes. However, you can run "Coupled Partitioning" and then the partitions do not have this restriction.
  Reply With Quote

Old   June 16, 2007, 14:30
Default Re: Multi domain performance penalty????
  #6
Gert-Jan
Guest
 
Posts: n/a
Hmmmm, learning every day. Since when does this option exists?

Gert-Jan
  Reply With Quote

Old   June 18, 2007, 06:46
Default Re: Multi domain performance penalty????
  #7
johnny
Guest
 
Posts: n/a
I think it has been an option for a long time. Definitely it was there in 10.0.
  Reply With Quote

Old   June 18, 2007, 08:32
Default Re: Multi domain performance penalty????
  #8
Gert-Jan
Guest
 
Posts: n/a
I started with CFX 5.3. It was not present there. Hard to keep up all the new features.......

Gert-Jan
  Reply With Quote

Old   June 18, 2007, 19:57
Default Re: Multi domain performance penalty????
  #9
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

Yes, it has been there for a while. I have played with it a long time ago for my simulations with a few GGIs in the hope it increased the simulation speed but it actually made it marginally worse. Not sure why.

I would be interested to hear if it works better now, or if it is an improvement for some simulations and not for others.

Glenn Horrocks
  Reply With Quote

Reply


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
Domain Imbalance HMR CFX 5 October 10, 2016 06:57
CFX domain comparison Kiat110616 CFX 4 April 3, 2011 23:43
Error Message after switching to multi domain physics chili023 CFX 3 June 5, 2010 06:28
Multi flow in two different domain arunss CFX 3 May 11, 2010 17:06
multi domain heat transfer prob mohammed zubair CFX 1 June 27, 2006 10:30


All times are GMT -4. The time now is 01:41.