# Can I run more than two kernels simultaneously on my MacBookAir laptop?

I'm running Version Number 10.0.1.0 with Platform Mac OS X x86 (32-bit, 64-bit kernel).

I have two Mathematica programs running using "Local" and "Alternative Local Kernel".

Is this the most I can use? (I did try adding a third ["New"], but there seemed to be a licensing issue.)

• Since you suspected it could be a licensing issue, it would make sense to tell us what license you have. Dec 28 '16 at 14:05

You can run as many kernels at the same time as your license allows. Your hardware does not matter.

Run

FilterRules[SystemInformation["Kernel"], "MaxLicenseProcesses" | "MaxLicenseSubprocesses"]


to find out the number.

"MaxLicenseProcesses" refers to main kernels—what you are looking at in the kernel configuration options.

"MaxLicenseSubprocesses" refers to subkernels—what you use with the parallel tools (Parallelize).

• Possibly the kernel for the frontend also counts, so that if you have a frontend then you can run "MaxLicenseProcesses" minus one kernels. Dec 28 '16 at 14:37
• @C.E. It does not count. Dec 28 '16 at 15:57
• Then I don't know how to explain this: the code gives "MaxLicenseProcesses" -> 8 but if I start four different versions of Mathematica (say 10.0, 10.1, 10.2, 10.3 and 10.4) I cannot start a fifth version (e.g. 11.0). If the frontend kernel does not count, then I should be able to start eight versions of Mathematica. Dec 28 '16 at 16:04
• Thanks--will try the suggestion (when either of my two currently running kernels terminates), Szabolics. I take it that licenses vary on the number allowed--no standard one for my version?. I only have one version at hand, not the several that C. E. appears to have. Well I did add a ["New"] kernel, but then when I tried to run it I got a licensing notice. So, maybe I'm limited to 2 (I don't know how "front end" considerations enter here.) Dec 28 '16 at 16:05
• @C.E. What is SystemInformation["FrontEnd", "MaxLicenseProcesses"] on your machine? I can run 6 versions concurrently with front ends. I can also run 7 (not 6) kernels in the terminals after having started a Front End (with its 2 kernels). The 8th one fails. I seem to have a license that allows 8 kernel and 8 front ends to run simultaneously. Dec 28 '16 at 16:11