Comment (by Ian Hinder):

Parallel compilation can be faster than serial compilation even on a machine with a single core, because the parallelisation hides filesystem latency. I remember noticing this on a machine with a particularly sluggish NFS filesystem. I don't know if this is relevant on this system

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2234/trouble-in-the-tutorial-server