I am using Ubuntu 22 and Mathematica 13. According to the description of my laptop I should have four CPU cores, as seen in the following screenshot:

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However, Mathematica only seems to recognize two kernels when attempting any parallel computation (see the following screenshot).

enter image description here

Am I seeing something wrong, or is there a way to tell Mathematica to use all four kernels?

Many thanks!

  • 2
    $\begingroup$ You have two physical cores - and four logical "cores" because of hyperthreading. Read here: support.wolfram.com/27877?src=mathematica "By design, Mathematica automatically launches subkernels equal to the number of physical CPU cores." $\endgroup$
    – flinty
    Jan 25, 2023 at 22:30
  • 2
    $\begingroup$ It also says: "To override this setting, use the LaunchKernels[n] function, where n is an integer indicating the number of local subkernels to launch." $\endgroup$
    – flinty
    Jan 25, 2023 at 22:31
  • 1
    $\begingroup$ And here is your CPU specs which indeed show only 2 physical cores: intel.com/content/www/us/en/products/sku/88193/…. Note that Intel likes advertising HyperThreading as doubling the number of cores, but security paranoid folks (e.g. OpenBSD) recommend to disable it to protect from side-channel attacks. $\endgroup$
    – Victor K.
    Jan 25, 2023 at 22:35
  • $\begingroup$ Since when having a support ticket answering a question is reason to close it? This could be consider a duplicate of this but I don't see how the Wolfram Support argument holds $\endgroup$
    – rhermans
    Jan 26, 2023 at 9:13