[boffin5]

Hi there,

Recently I got my more capable desktop PC up and running; it has an AMD EPYC 4313P processor with 16 cores. Now the problem is getting programs to run with it. Initially I am try to run OF simulations using 6 cores.

Right off the bat I found that I have to add 'oversubscribe' after the mpirun command, as in:

mpirun -oversubscribe -np 6 -parallel

But the run still failed, with this message:

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  8
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
Build  : 8-1c9b5879390b
Exec   : snappyHexMesh -dict system/snappyHexMeshDict.1 -parallel -overwrite
Date   : May 31 2022
Time   : 11:31:10
Host   : "boffin5-VirtualBox"
PID    : 2822
I/O    : uncollated
[0]
[0]
[0] --> FOAM FATAL ERROR:
[0] "/home/boffin5/cfdaero/rad6/system/decomposeParDict" specifies 6 processors but job was started with 2 processors.
[0]
FOAM parallel run exiting
[0]

So ubuntu still thinks I have 2 cores. So I went to msconfig, and in the advanced boot setting, changed the number of processors to 16 (see attached image). Then rebooted.



Next, in the ubuntu terminal I entered 'lscpu' to see my system configuration. The output:

boffin5@boffin5-VirtualBox:~$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   48 bits physical, 48 bits virtual
CPU(s):                          2
On-line CPU(s) list:             0,1
Thread(s) per core:              1
Core(s) per socket:              2
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       AuthenticAMD
CPU family:                      25
Model:                           1
Model name:                      AMD EPYC 7313P 16-Core Processor
Stepping:                        1
CPU MHz:                         3000.002
BogoMIPS:                        6000.00
Hypervisor vendor:               KVM
Virtualization type:             full
L1d cache:                       64 KiB
L1i cache:                       64 KiB
L2 cache:                        1 MiB
L3 cache:                        128 MiB
NUMA node0 CPU(s):               0,1
Vulnerability Itlb multihit:     Not affected
Vulnerability L1tf:              Not affected
Vulnerability Mds:               Not affected
Vulnerability Meltdown:          Not affected
Vulnerability Spec store bypass: Vulnerable
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user
                                  pointer sanitization
Vulnerability Spectre v2:        Mitigation; Retpolines, STIBP disabled, RSB fil
                                 ling
Vulnerability Srbds:             Not affected
Vulnerability Tsx async abort:   Not affected
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtr
                                 r pge mca cmov pat pse36 clflush mmx fxsr sse s
                                 se2 ht syscall nx fxsr_opt rdtscp lm constant_t
                                 sc rep_good nopl nonstop_tsc cpuid extd_apicid
                                 tsc_known_freq pni ssse3 cx16 sse4_1 sse4_2 hyp
                                 ervisor lahf_lm cmp_legacy cr8_legacy 3dnowpref
                                 etch vmmcall fsgsbase arat

My understanding is that for my 16 core processor, the line with CPU(s) should read 16, not 2.


As a last resort, I looked into the system BIOS, and made this change:


Aptio Setup -AMI
Advanced
CPU Configuration
Core Control [seven (7+0)] ...........(this was previously set to [AUTO])


I'm not sure about the 'seven', but that was the biggest option, so I figured that it might correspond to 16 cores (??) I didn't see any other place to specify the number of cores used.


After all this, my program still fails, with the same message.


Can someone help me untangle this Gordian knot?

[flotus1]

In bios, you can only lower the number of active cores. If you want all cores, you have to leave that setting on auto.
Is my guess correct that you are running Windows 10 as a host OS, and then OpenFOAM inside of some virtualized environment? Virtualbox as it seems...
Then the problem is with this layer, not on the bios level. Switch core control back to auto, check if all cores are enabled in the host OS, and work from there.
I am not exactly the worlds leading expert on virtualization. What I can say is if you don't want to leave a lot of performance on the table for OpenFOAM, don't use Virtualbox. There is WSL as an alternative, but from the benchmarks I have seen, it is also significantly slower than bare metal.