[student666]

Hi all,

just a silly question.
I'm running an icoFoam simulation using parallel computing with 4 cores

mpirun -np 4 icoFoam -parallel

my silly question concerning what i see on task manager. (enclosed a picture)

I see that 4 task are running (icoFoam -parallel), but CPU usage is about 25% each.
So my doubt rise frome thinking: 25%*4=100%.

The calculation (1700000 cells fully hexahedral) is going very slowly, I expected a quicker running.

The question is:
Is it possible to run a simulation by decomposing the case (I use scotch) into 4 cores, but the system uses only one?
Or other way, If I have 4 cores but I decompose into 6 core, parallel computing starts anyway?

Thanks for any help.

Michele

[LaSerpe]

I guess you're running on your personal machine, what are its spec?

[student666]

Hi Giulio,

yes it's my personal machine; I think you're asking for the following (I edit the post):

michele@KebaXubuntu:~$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 37
Stepping:              2
CPU MHz:               2400.000
BogoMIPS:              4787.88
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              3072K
NUMA node0 CPU(s):     0-3

and

michele@KebaXubuntu:~$ cat /proc/cpuinfo
processor    : 0
vendor_id    : GenuineIntel
cpu family    : 6
model        : 37
model name    : Intel(R) Core(TM) i5 CPU       M 520  @ 2.40GHz
stepping    : 2
microcode    : 0x9
cpu MHz        : 2400.000
cache size    : 3072 KB
physical id    : 0
siblings    : 4
core id        : 0
cpu cores    : 2
apicid        : 0
initial apicid    : 0
fpu        : yes
fpu_exception    : yes
cpuid level    : 11
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm ida arat dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4787.79
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

processor    : 1
vendor_id    : GenuineIntel
cpu family    : 6
model        : 37
model name    : Intel(R) Core(TM) i5 CPU       M 520  @ 2.40GHz
stepping    : 2
microcode    : 0x9
cpu MHz        : 2400.000
cache size    : 3072 KB
physical id    : 0
siblings    : 4
core id        : 2
cpu cores    : 2
apicid        : 4
initial apicid    : 4
fpu        : yes
fpu_exception    : yes
cpuid level    : 11
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm ida arat dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4787.89
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

processor    : 2
vendor_id    : GenuineIntel
cpu family    : 6
model        : 37
model name    : Intel(R) Core(TM) i5 CPU       M 520  @ 2.40GHz
stepping    : 2
microcode    : 0x9
cpu MHz        : 2400.000
cache size    : 3072 KB
physical id    : 0
siblings    : 4
core id        : 0
cpu cores    : 2
apicid        : 1
initial apicid    : 1
fpu        : yes
fpu_exception    : yes
cpuid level    : 11
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm ida arat dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4787.88
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

processor    : 3
vendor_id    : GenuineIntel
cpu family    : 6
model        : 37
model name    : Intel(R) Core(TM) i5 CPU       M 520  @ 2.40GHz
stepping    : 2
microcode    : 0x9
cpu MHz        : 2400.000
cache size    : 3072 KB
physical id    : 0
siblings    : 4
core id        : 2
cpu cores    : 2
apicid        : 5
initial apicid    : 5
fpu        : yes
fpu_exception    : yes
cpuid level    : 11
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm ida arat dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4787.88
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

I'm not too much expert on this stuff, what do you think aoubt it?

Thanks

Michele

[student666]

I edit previous post as was incomplete on cat /proc/cpuinfo command line

[LaSerpe]

seems ok, instead of using task manager, try with top and look at what it says.
Looking at the picture you posted first, I can see 4 processes running, ie one for each processor

To me task manager is showing a misleading info, probably that's a percentage calculated from the total CPU (made of 4 proc, so 25% is the amount associated to 1 proc)

top should tell info about every single processor, (works this way on my ubuntu), just try

Giulio

[student666]

Yes, you're right, task manager is telling me "lies", by prompting command line top, I can see all 4 cores are using 100% each.

Ciao e grazie!

[jherb]

In the top tool you can switch the settings of how the percentage is calculated (it is called IRIX mode), see the help page (press h):

  1,I       Toggle SMP view: '1' single/separate states; 'I' Irix/Solaris mode

If IRIX mode is turned off all processes are add up to 100 % whereas if IRIX mode is turned on the percentage is given per processor. I guess you can also change this in you task manager.

[student666]

Thank you Herb for the suggestion, but I'm not able to do it. Anyway, I'm able to do it by typing "top".

Bye.

Michele