4 x E7-4870 is folding on 32 cores only?

A

-alias-

Limp Gawd
Joined
Jul 15, 2012
Messages
374
Very strange, It should be no problem for only 80 threads. The hard limit for fah6 (Gromacs 4.5) I found is 512 threads.
 
I am guessing that '80' is not a good number since it does fall in the range of 2^x. Try '-smp 64'. I know that '-smp 40' or '-smp 44' defaults back to 32 cores/threads.
 
Under Windows it can fold at all cores, but with only 80% load, so the main question is, why not under Linux? I am not sure I believe the theory of bad number.:D
 
You realize, 80% of 80 is 64 right. It seems that windsows is defaulting to 64 and balancing the load across all cores, where as the *nix one is going back to is default of 32.
 
Thanks, I will know more after the weekend. Right now it is folding under Ubuntu 11.10 with a TPF for 8101 in about 12min. So it is produces some thing like 400K PPD at the moment, hopefully at all 40/80 cores/threads.

This is not my server, it belongs to a friend that I communicate with on another forum in Norway, and I do not have directly access to the machine.
 
Your friend is probably looking at Ubuntu's system monitor which was limited to reporting 32 cores in earlier Ubuntu versions.

Use the command-line for optimal results (top and ps -L auxw for starters).
 
-smp 80 works just fine.

What do you get back when you do: grep CONFIG_NR_CPUS /boot/config-X.Y.Z (where X.Y.Z is your kernel version)?

Patonb hit the nail on the head as to why Windows will only load the system up to 80%. Windows uses a rather clumsy implementation for supporting >64 logical processors called "Processor Groups." For this reason, you will have what amounts to essentially two separate clusters on the machine, one with 64 threads and one with 16 threads. You can change Processor Group membership manually, but no single Processor Group can exceed 64 logical processors.

edit - Actually, tear's probably right. 400k is only about 10% shy of what E7-4870s should be doing on a P8101.
 
Thanks again all of you! My forum friend is reading this thread so I believe he will do the test you suggest after the weekend. He was in a hurry to make the server fold before this weekend came along, so maybe he did not have the time to install the Kraken before he left the building.
 
I concur with tear and Deadthings... smp -80 does work.
And don't use ubuntu system monitor it only goes up to 32 threads....

tear knows the tpf /ppd it should get as well... he helped me get turbo working on an e7-4870 4p last summer...
 
You must log in or register to reply here.
Back
Top