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

Thoughts on Openbenchmarking.org

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 6, 2022, 09:14
Default Thoughts on Openbenchmarking.org
  #1
Senior Member
 
Simbelmynė's Avatar
 
Join Date: May 2012
Posts: 529
Rep Power: 14
Simbelmynė is on a distinguished road
Hey,


So over at https://openbenchmarking.org/test/pts/openfoam we have some nice up-to-date information about current CFD hardware. I am curious what your thoughts are when it comes to the 30M vs 60M test cases, especially in the lower tiers (e.g. 5900X vs 12900k). 5900X performs reasonably well at 30M cells, but for 60M cells it is surpassed even by the 7700k. This really does not make sense to me. Does the extra cache give benefits for the 30M case but not for the 60M case, or is it something else?
Simbelmynė is offline   Reply With Quote

Old   January 7, 2022, 07:44
Default
  #2
Super Moderator
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,218
Rep Power: 44
flotus1 has a spectacular aura aboutflotus1 has a spectacular aura about
This site has come up from time to time. And each time I looked at it, I was just baffled by the results. Many of them just don't make any sense, as you found out yourself. Not sure what to make of it
Some of the oddities you describe could be explained by different memory configurations. I.e. simply not enough memory on one of the systems to run the 60M case in-core. But then again, what's the point of keeping such results.
flotus1 is offline   Reply With Quote

Old   January 7, 2022, 09:01
Default
  #3
Senior Member
 
Simbelmynė's Avatar
 
Join Date: May 2012
Posts: 529
Rep Power: 14
Simbelmynė is on a distinguished road
Yes I agree. Strange though that there are many such reported results and that the spread is quite low.



Another thing that seems a bit suspicious is the number of CPUs. I have a hard time believing a single 7763 is as good as 2 x 7453. Perhaps it is manual user input that is behind such reports? The idea is good though and the overview is much better compared to our in-house solution here at cfd-online
Simbelmynė is offline   Reply With Quote

Old   January 7, 2022, 16:18
Default
  #4
Super Moderator
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,218
Rep Power: 44
flotus1 has a spectacular aura aboutflotus1 has a spectacular aura about
The Epyc 7453 is a special case. With only 64MB of L3 cache, it is the weakest CPU in the whole lineup. Possibly with only 2 CCDs enabled, and thus reduced effective memory bandwidth. A single 7763 has to be faster than 2 of these.

The main issue is probably that these results are all crowd-sourced. And I don't know how much effort goes into verifying the results uploaded to the database. What's the memory configuration? Bios settings? Operating system?
There are just too many variables in play. Benchmarking with consistent results isn't easy, even people who do it for a living get it wrong sometimes.
flotus1 is offline   Reply With Quote

Old   January 7, 2022, 19:42
Default
  #5
Senior Member
 
Simbelmynė's Avatar
 
Join Date: May 2012
Posts: 529
Rep Power: 14
Simbelmynė is on a distinguished road
2 x 7F72 is only about 10% faster than the 7763. So although I hear what you say about the gimped 7453, I still think this is strange, unless perhaps Milan is really that good. Also, the standard deviation is really low for many of the benchmarks. I am not sure if that indicates that the same person has submitted several benchmarks for the same system. We have much larger variations in our benchmark thread here, with respect to the variables you mention.
Simbelmynė is offline   Reply With Quote

Old   January 14, 2022, 00:04
Default
  #6
Member
 
Yan
Join Date: Dec 2013
Location: Milano
Posts: 38
Rep Power: 11
aparangement is on a distinguished road
Send a message via Skype™ to aparangement
I've tried (half a year ago?) to run its benchmark by myself.

However even the "30M" case would use up the 256G RAMduring snappy mesh. I tried to setup a coarser mesh however my wall time is not comparable at all with the his report, even compare with the 30M setup (something like 20 minutes vs 30 seceonds, maybe the reported endtime is not the same as the clean case provieded).

Then I gave up digging...

I agree that the results are not in consistent with each other, althogh I don't have proof..
I highly suspect that some of the too fast cases are due to crashed simulaiton..

Quote:
Originally Posted by Simbelmynė View Post
Hey,


So over at https://openbenchmarking.org/test/pts/openfoam we have some nice up-to-date information about current CFD hardware. I am curious what your thoughts are when it comes to the 30M vs 60M test cases, especially in the lower tiers (e.g. 5900X vs 12900k). 5900X performs reasonably well at 30M cells, but for 60M cells it is surpassed even by the 7700k. This really does not make sense to me. Does the extra cache give benefits for the 30M case but not for the 60M case, or is it something else?
aparangement is offline   Reply With Quote

Old   January 16, 2022, 09:17
Default
  #7
Senior Member
 
Ford Prefect's Avatar
 
Join Date: Mar 2009
Posts: 138
Rep Power: 15
Ford Prefect is on a distinguished road
Yeah something is a bit fishy. If there are crashed cases I would have guessed that the standard deviation would be larger though. But I think that is a plausible reason for the strange results.
__________________
"Trying is the first step to failure." - Homer Simpson
Ford Prefect is offline   Reply With Quote

Old   February 16, 2022, 02:36
Default
  #8
Member
 
Guy
Join Date: Jun 2019
Posts: 34
Rep Power: 5
linuxguy123 is on a distinguished road
Quote:
Originally Posted by flotus1 View Post
The main issue is probably that these results are all crowd-sourced. And I don't know how much effort goes into verifying the results uploaded to the database. What's the memory configuration? Bios settings? Operating system?
There are just too many variables in play. Benchmarking with consistent results isn't easy, even people who do it for a living get it wrong sometimes.

So true. Want proof ? Go over to www.geekbench.com and compare the ratings people get on the same processor. It is not unusual to find a 2:1 rating difference between the fastest and the slowest.


Great discussion.
linuxguy123 is offline   Reply With Quote

Reply

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
Some fundamental thoughts about turbulence modeling... Avr.Tomer Main CFD Forum 9 September 27, 2019 23:34
CFX 12 in WB 2.0 - Your thoughts? flattie ANSYS 0 May 13, 2009 20:05
OpenFOAM: General thoughts?? open Main CFD Forum 5 September 9, 2006 09:08
thoughts on the different companies Jason Main CFD Forum 0 July 13, 2005 21:18
Thoughts about Courant-Friedrich Levy rate Hamm Main CFD Forum 6 June 3, 2004 05:51


All times are GMT -4. The time now is 19:39.