24cores job slower than 12cores job on abaqus explicite??!!!!

[ludoLLN]

Hello everybody and especially dag84,

As Dag84, we have bought a server with 32cores instead of 12cores before, we have 19 tokens and can so launch jobs on 24 cores maximum.
Up to now (we bought the station 1 month ago), cpu time with theses jobs on 24 cores are longer than those launched on 6 or 12cores on the old and new machine!!
We are excusively using abaqus explicite with highly non-linear (large-strain) problems.
If somebody has solved such an issue by configuring the workstation or using specific options when laucnching the job (parallelization method, domain size, etc...), I am interested!!

Thanks for your help.
Ludovic.
France.

 

[StefCon]

Hello,
I'm guessing now but when you say 32 cores you mean 32 threads. Assuming you have Intel xeons (2 of them), the maximum number of physical cores are right now 8 per CPU. So you got 16 cores. By using Intel's hyperthreading you get twice as many threads. For applications that scale perfectly or if you run one program per thread, hyperthreading increase the maximum cpu throughput by approximately 15% (source needed ). Since Abaqus does not scale as well, you should simply only use 16 parallel processors when you are running your jobs. The windows activity manager will say that you use 50% CPU but that is a lie! You max it out. I've also read that it is recommended to disable hyperthreading in the PC's BIOS.

If this solves your problem or not I'm not sure of. Hope it does.

/S

 

[ludoLLN]

Thank you StefCon,

We have in fact 4 cpus with 8 cores for each and as recommended by abaqus we have disabled the hyperthreading.
To be more precise on the workstation:
Serveur X3750M4 4 processor 8Cores (type E5-4600)
8 x (8GB (1x8GB,2Rx4,1.5V) PC3-12800 CL11 ECCDDR3)
System software: Linux

Regards
Ludovic

 

[StefCon]

Hi,
That is a nice machine for sure! In that case I'm all out of ideas. I saw some graphs Dassult Systemes did themselves where the analysis time started to increase when going from 32 to 64 threads. Maybe in rare circumstances this number is lower. Does your problem persist for all models? Maybe your hard drive performance is limiting? Perhaps the Linux kernel you are using needs a fix.

Please let me know if you find an answer,
Best regards,
S