Why is MATLAB unable to detect the presence of multiple cores on my machine running Redhat Linux 5.x?

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MathWorks Support Team on 27 Jun 2009

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Edited: MathWorks Support Team on 13 Feb 2018

I am using MATLAB on an AMD Dual Core Opteron Processor 285 machine running Redhat Linux 5.x, however, MATLAB is unable to detect the presence of multiple cores on my machine. When I check the number of cores detected by MATLAB as follows:

feature ('Numcores')

MATLAB detects only one core on my machine.

 ans = 
 1

I checked the number of cores detected by my operating system using the following command from the Linux shell

cat /proc/cpuinfo

The output is as follows:

 processor       : 0
 vendor_id       : AuthenticAMD
 cpu family      : 15
 model : 33
 model name      : Dual Core AMD Opteron(tm) Processor 285
 stepping        : 2
 cpu MHz         : 2592.654
 cache size      : 1024 KB
 fpu     : yes
 fpu_exception   : yes
 cpuid level     : 1
 wp      : yes
 flags   : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext lm 3dnowext 3dnow pni ts fid 
 bogomips        : 5062.25
 TLB size : 1088 4K pages
 clflush size    : 64
 cache_alignment : 64
 address sizes : 40 bits physical, 48 bits virtual
 power management : tis fid vid ttp

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MathWorks Support Team on 27 Jun 2009

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https://www.mathworks.com/matlabcentral/answers/99177-why-is-matlab-unable-to-detect-the-presence-of-multiple-cores-on-my-machine-running-redhat-linux-5-x#answer_108524

Edited: MathWorks Support Team on 13 Feb 2018

From the '/proc/cpuinfo' output it is evident that the Operating System does not recognize the presence of two cores on the machine. If multiple cores are detected, one would see multiple outputs (one for each of the cores) similar to the one shown above. MATLAB's number of cores information reflects the number detected by the Operating System.

The OS could be detecting the wrong number of cores for one of the following reasons:

1. It could be that the machine's OS kernel is not SMP (symmetrical multi processor) aware. To confirm this one can execute the following command at the shell:

uname -a

If the word 'SMP' is present in the output, it means that the kernel is SMP aware.

2. There have also been reports that indicate this could be a hardware issue with the Linux box. For example, searching for "Redhat 5 SMP cpuinfo" on Google, brings up a page like this where such issues are discussed.

http://www.vbulletin.com/forum/showthread.php?t=256355